The Grower April/May 2018

The

GROWER THE TECHNICAL JOURNAL FOR HORTICULTURE

Issue No. 239

Apr/May 18

BEYOND THE HORIZON How can UK businesses turn Brexit gloom into an opportunistic boom?

BUZZED OFF Addressing the productivity issues of native bumble bees

KNOWING YOUR ENEMY

Could studying vine weevil behaviours provide a viable long-term control solution for UK growers?

Stay one step ahead of

crop pests AHDB’s forecasting and monitoring services can help you find out when pests are most likely to be in your crops Head to horticulture.ahdb.org.uk/ahdb-pest-bulletin to access:

●● AHDB Aphid News ●● AHDB Pest Bulletin ●● AHDB Pest Blog

Receive free pest prediction alerts straight to your inbox

horticulture.ahdb.org.uk/ahdb-pest-bulletin

ACKNOWLEDGEMENTS If you wish to get in touch with our team about any aspect of this publication please use the following contact details:

COMMENT

GENERAL ENQUIRIES hort.info@ahdb.org.uk EDITORIAL

Steve Tones, Strategy Director, AHDB Horticulture steve.tones@ahdb.org.uk

Luke Garner Technical Writing Manager luke.garner@ahdb.org.uk Haroon Jabar Marcomms Senior Manager - Horticulture haroon.jabar@ahdb.org.uk KNOWLEDGE EXCHANGE

Debbie Wilson Head of Knowledge Exchange - Horticulture debbie.wilson@ahdb.org.uk DESIGN

Denis Hanlon Graphic Design denis.hanlon@ahdb.org.uk SUBSCRIPTIONS AND MAILING

Vicky Horbury Customer Relationship Coordinator comms@ahdb.org.uk IMAGE CREDITS

EPPO - page 9 Gary Naylor Photography – page 11 (Main image) Belish/Shutterstock.com - page 11 Twocoms/Shutterstock.com - page 11 Daphne Wong – page 16 Roma Gwynn - page 19 Harper Adams University – front cover; page 20

This publication is brought to you by AHDB For more information contact:

AHDB Horticulture Stoneleigh Park Kenilworth Warwickshire CV8 2TL T: 024 7669 2051 E: comms@ahdb.org.uk W: horticulture.ahdb.org.uk @AHDB_hort If you no longer wish to receive this information, please email us on the address above.

WHEN THE TOUGH GET GOING With the new season upon us, AHDB’s technical teams are now busily planning the major new research programmes on diseases and pests identified by sector panels.

We invest roughly two-thirds of the horticulture levy on crop protection.

This has largely been enough to support the ‘spray-and-kill’ approach to crop protection on which horticulture has depended for the last seventy years, but the future management of pests and diseases will increasingly rely on our ability to manipulate the various genetic, biological and agronomic factors that contribute to crop resilience.

For this we need long-term research programmes co-funded by the research councils and ways of sharing our costs and knowledge with research funders and providers elsewhere in the world.

With Brexit looming, the rising cost of labour poses a big threat and the spectre of unplanted land and crops rotting unharvested in fields is already with us.

This is why we are pushing ahead with more labour efficiency workshops, to enable everyone to make the best possible use of whatever labour they have.

I attended Fruit Logistica for the first time in February, and walking past countless suppliers of exotic produce from all over the world, I could not help but be impressed. I fear this rising tide of imports will continue to swell our supermarket shelves.

However the amount of trade being done by British produce companies was just as impressive. For the tiny outlay of levy funding and DIT cofunding involved, British growers have been able to put themselves at the heart of international trade. I saw for the first time just how important the exporting of British produce, knowledge and technological expertise is for our future.

I returned inspired by the energy, vision and entrepreneurial drive of the British growers I met, and with my faith in the future of British horticulture restored. Things are undoubtedly tough for many at the moment, but the tough are getting going; it’s a very fine industry to be part of.

© Agriculture and Horticulture Development Board 2018.

While the Agriculture and Horticulture Development Board seeks to ensure that the information contained within this document is accurate at the time of printing, no warranty is given in respect thereof and, to the maximum extent permitted by law the Agriculture and Horticulture Development Board accepts no liability for loss, damage or injury howsoever caused (including that caused by negligence) or suffered directly or indirectly in relation to information and opinions contained in or omitted from this document.

All rights reserved.

Apr/May 2018 3

CONTENTS 5 Contributors 6 News and updates

PROTECT

IN FOCUS

17 EAMU latest AHDB’s Bolette Palle Neve brings you up-to-date on all things EAMU

8 Lessons on lettuce Fusarium wilt Insights from a technical review to help UK growers manage Lettuce Fusarium wilt

18 Biopesticides – your questions Warwick Crop Centre’s Dave Chandler answers your questions about biopesticides

10 Beyond the horizon AHDB’s Steve Tones weighs up the Brexit challenges and opportunities for horticulture

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20 Knowing your enemy Studying vine weevil biology and behaviour to help keep them under control

LABOUR & LOGISTICS 30 The productivity puzzle UK productivity is mostly unchanged in a decade - how can horticulture buck the trend?

INNOVATE

12 The art of making some green Which new varieties could hold the key to significant financial gains for vining pea growers?

32 A.I. brain over manual brawn Could a fully automated broccoli harvester soon be a commercial reality?

24 Staying ahead of Xylella’s spread Investigating the measures being put in place to tackle the spread of Xylella

RESOURCE MANAGEMENT 26 Staying in control How to manage humidity and ensure greenhouse climate control

4 AHDB Grower

34

22 Plugging the gaps Discover the latest exciting successes from AHDB’s SCEPTREplus project

CULTIVATE

16 Producing perfect produce by parthenocarpy Can the traditional methods of cucurbit pollination be bypassed successfully?

28 Crop variability – is the answer in the soil?

Understanding soil and crop variability on the farm

21 Defying problem weeds John Atwood, ADAS, reveals the promising new stars of the weed control world

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14 Buzzed off Examining the fallout of the switch from non-native to native bumblebees in tomato crops

27 Time is up for trickle exemptions The vital facts you need to know about changes to water abstraction licences

VIEWPOINT 34 Insider insight: Past lessons in currant-lettuce aphid Gemma Hough reveals how an AHDB-funded studentship helped her achieve her career goals 35 Hort thought: environmental strategy We ask you whether you’re on board with the government’s new environmental strategy

CONTRIBUTORS Discover more about the people who have helped to contribute to this issue of The Grower magazine

ROB JACOBSON Dr Rob Jacobson is an independent IPM consultant with over 30 years’ experience in biological pest control. He has a successful history of implementing IPM in commercial crops with clients as far afield as Australia. Rob has a proven record of managing and delivering R&D projects for government organisations, AHDB and many private companies. He is a member of the Tomato Growers’ Association Technical Committee and is active in several IPM-related organisations. He has won the ‘Science into Practice’ category at the Grower of the Year Awards for his work on IPM in tomato crops.

Rob is buzzing with excitement at news of tomato pollination on page 14

DAVE CHANDLER Dave is a microbiologist and entomologist. His main areas of interest are: insect pathogens and microbial pest control; bee health; ecology and physiology of entomopathogenic fungi; biopesticide regulation and governance; and Integrated Pest Management (IPM).

Dave has worked at Warwick Crop Centre since 1990. Previous to this, he studied for a bachelor degree in biology at the University of Nottingham, followed by a PhD in mycology at Kings College London. He is a Fellow of the Royal Entomological Society, has been an adviser on IPM to the European Parliament and a research programme assessor for the US Department of Agriculture.

Dave takes your questions about biopesticides on page 18

NICOLA DUNN Nicola is an Environmental Chemist working in AHDB’s Resource Management Team with a specific focus on water. She is currently building a cross-sector programme of research and knowledge exchange on all things water-related, such as water quality and water resources. She also manages some carrot and Brassica research projects for AHDB Horticulture. Nicola joined AHDB in 2017 after seven years with the National Farmers’ Union working on environmental policy issues including water quality, NVZs, nutrient and soil management and waste. She is interested in the translation of research into on-farm change and ensuring a balance between environment and agriculture.

Nicola abstracts the key points from the new trickle exemptions guidelines on page 27

LIZZIE SAGOO Lizzie is a Principal Soil Scientist at ADAS with specialist knowledge of soil and nutrient management and diffuse pollution of air and water from agricultural systems.

Lizzie joined ADAS in 2003 following a PhD at the University of Leeds. She led the recent RB209 review of crop nutrient management and nutrition for horticultural crops for AHDB. In addition to the AHDB Horticulture precision farming project, Lizzie also leads a Cereals & Oilseeds project looking at the Sulphur requirements of oilseed rape and a Beef & Lamb project on integrating beef production into arable units on temporary grass leys.

Find out what causes variability in your soil with Lizzie on page 28

Apr/May 2018 5

NEWS & UPDATES IN BRIEF OPEN FOR BUSINESS RODENTICIDE RESISTANCE

A recent study by Reading University confirms that rats in some parts of the country are resistant to some of the most widely-used poison baits.

The report states that the study ‘shows the massive extent of L120Q resistance across the whole of central southern England’.

DIAMONDBACK MOTHS OVERWINTERING IN SOMERSET Diamondback moth (DBM) caterpillars have been found surviving in UK Brassica crops this winter and growers are recommended to check their own crops for the pest now. The caterpillars were discovered on the underside of leaves in un-netted swede crops.

NEW CROP PROTECTION FACTSHEETS

AHDB has published two new factsheets to help growers to control important pests. ‘Tarsonemid mite on strawberry’ provides information on cultural, biological and chemical control options, including introduction rates of predatory mites. ‘Leaf and bud nematodes in hardy nursery stock’ offers guidelines on symptom recognition and management options. Visit horticulture.ahdb.org.uk/publications.

HEALTH AND SAFETY IN PROTECTED EDIBLES PRODUCTION

A film has been produced by AHDB to enable workers, supervisors and managers in glasshouses to keep themselves safe by understanding and preparing for specific risks, such as working at height and in humid conditions. Available in eight languages on YouTube, just search ‘Horticulture TV’.

6 AHDB Grower

Horticulture and Potatoes exporters travelled over to Berlin, Germany for the annual exporting merry-go-round at Fruit Logistica The UK’s exit from Europe did not cast a shadow over the business and relationships that British fresh produce exporters created and built on at Fruit Logistica 2018.

There is a lot of business done in terms of export potential but there is quite a bit of domestic business completed because you have the retailers out here in big numbers.”

Six exporters (Bedfordshire Growers, Isle of Ely, James Hutton Ltd, AC Goatham and son, Angus Soft Fruits and JEPCO) joined AHDB on the British pavilion to showcase Great Britain’s horticulture and potato industries.

The AHDB stand provides a focused hub to do business and champion the UK’s reputation for outstanding food and farming. The exhibitors had dedicated branded exhibition booths, meeting space, and networking opportunities in a fully managed and catered stand.

Departing AHDB Horticulture Chairman, Gary Taylor, said, “If you are a grower, it is difficult to justify having a stand on your own. Being a part of a bigger stand attracts more people in and you have the added backing of the GB brand.

Richard Pett, Jepco, said, “This event allows us to cement our relationship with current partners both from the UK and abroad but we have also taken the chance to build further opportunities across wider Europe.

I’m really impressed by the new AHDB stand this year; it’s bigger, it’s brighter, it’s more welcoming and that is particularly important with what is happening with Brexit. We want the world to know that Britain is open for business and active on the international stage Michael Barker, Editor, Fresh Produce Journal

NEWS & UPDATES

SPINOSAD RESISTANCE FOUND IN ONION THRIPS A population of onion thrips, collected in the south of England, has been found to contain thrips resistant to spinosad, one of the few effective treatments currently available to growers.

Steve Foster, Rothamsted Research, screened a thrips sample collected from salad onions following reports that Tracer did not appear to be as effective as usual. His tests confirmed that individuals in the population collected had developed resistance to spinosad, the main active in Tracer, when it was applied at the field rate in his bioassays.

Thrips are a group of insects which are prone to insecticide resistance and resistance to pyrethroid insecticides in English populations was confirmed by Steve Foster’s research some years ago.

While the spinosad-resistant populations might not yet be widespread in the UK, growers should review their

integrated pest management strategies to reduce the risk of further resistance development.

Dawn Teverson, Knowledge Exchange Manager, AHDB said: “It’s really important that growers know whether a product is going to be effective against the target pest; there seem to be more and more pests showing insecticide resistance.”

Rosemary Collier, Director, Warwick Crop Centre said, “This research highlights how important it is to maintain the capability to monitor pests for insecticide resistance in the UK.” The AHDB SCEPTREplus crop protection programme is currently reviewing the commissioning of trials to find new controls for this pest on leek and other crops in light of the new information on insecticide resistance.

GET YOUR HANDS ON GREATSOILS Getting GREATsoils is high on the agenda for many growers, but understanding which practical measures will have the biggest impact on soil health, and how to test that what you’re doing is actually making a difference, is often challenging.

As part of the AHDB GREATsoils programme, a wealth of resources have now been published to provide clear recommendations and advice to help growers get the best from their soils.

If you’re interested in earthworm counts, soil respiration or infiltration tests, but are not sure how best to implement them in your growing systems, the series of bite-size soil testing instruction videos will help.

A series of published case studies explain how changes to soil management have made a significant difference to commercial horticultural crop production; from Cobrey Farms, asparagus growers who have installed grassed waterways to prevent soil erosion, to Fresh Growers Ltd., who have reviewed the best soil testing methods for carrot production.

Grace Choto, Knowledge Exchange Manager at AHDB, said, “Many growers are actively looking to improve their soils as its one of their most valuable resources. However, understanding how to test soils, what to look for, and importantly how to make the right decisions based on the data from soil testing can be challenging.

We have produced a range of factsheets and videos that we hope will make getting GREATsoils easier.”

Other factsheets in the range include the importance of soil pH and the benefits of compost to soil health.

The resources can be found via horticulture.ahdb.org.uk/ greatsoils Apr/May 2018 7

LESSONS ON LETTUCE FUSARIUM WILT

In response to the recently confirmed outbreak of lettuce Fusarium wilt in the UK, AHDB commissioned Dr Andrew Taylor, University of Warwick, to produce a technical review on the current available knowledge to help UK growers manage this potentially damaging disease

The lettuce wilt outbreak, caused by Fusarium oxysporum f. sp. lactucae (FOL), has been identified as race 4 (FOL4), the same pathogen causing serious challenges to protected lettuce production in the Netherlands and Belgium. Effective control measures are currently limited.

It is likely that a very low level of FOL4 inoculum was introduced into the UK initially, leading to low or undetectable levels of infection. Subsequent cropping in the same area led to a build-up and spread of inoculum, until sufficient spores were present to cause economically damaging levels of disease.

Though FOL is specific to lettuce and will not cause symptoms on other crops, it can colonise and multiply on the roots of a range of other crop (e.g. spinach) and weed hosts. Leaving soils fallow and weed-free, and reducing the intensity of cropping can help to prevent build-up of inoculum in the soil.

STOPPING THE SPREAD

The main way FOL is transmitted appears to be through infested soil, which can be spread on farming equipment, trays, pallets, plants and footwear. Hygiene measures are therefore crucial to prevent the spread of the disease.

8 AHDB Grower IN FOCUS

Quaternary ammonium compounds are one of the most effective disinfectants for F. oxysporum. However, many disinfectants are less effective in the presence of soil. Trays and pallets moved between growers and propagators need to be thoroughly cleaned of soil and plant material to enable disinfectants to be effective.

Kim Parker, Crop Protection Scientist at AHDB, said, “It will take the whole industry working together to ensure good hygiene is in place across the entire supply chain to prevent the disease from taking hold in the UK.” In Italy, FOL race 1 has been detected at very low levels on seed. While transmission of FOL4 via seed is possible, the significance of this route of transmission is unclear and it cannot explain the rapid spread of FOL4 across the Netherlands and Belgium.

EFFECT OF TEMPERATURE

Like other Fusarium wilts, evidence from the Netherlands suggests that FOL4 may have a preference for higher temperatures.

Some growers have resorted to growing protected lettuce only in the cooler months of the year and growing crops such as fennel, pak choi and endive in the warmer summer months.

However, outdoor growers should be aware that FOL4 may still be able to cause substantial disease at lower temperatures as a high level of Fusarium wilt was observed in a protected lettuce crop grown in Lancashire in December 2017 when air temperatures were only 8°C. CONTROL OPTIONS

Resistant cultivars would offer the best control option for FOL. While there is some resistance to FOL4, particularly in outdoor lettuce types, no indoor butterhead cultivars are resistant, although breeding work is in progress.

If an outbreak of lettuce FOL is suspected, soil disinfestation before re-cropping is a priority. Disinfestation using steam or Basamid (dazomet) can reduce disease incidence by more than 90%. Repeat treatments are required, with at least one treatment per year.

There may be scope to incorporate biologicals into soil after disinfestation to improve the efficacy and longevity of treatment, but this requires further investigation.

Biofence (Brassica carinata pellets) is available in the UK as a soil amendment to be incorporated before planting.

Italian researchers showed that Biofence applied 14–60 days prior to lettuce

IN FOCUS transplanting reduced disease severity by up to 80% for FOL race 1.

A table of fungicides and biological control agents that are currently approved for use on lettuce in the UK and with reported activity against F. oxysporum is available in the full report.

Products should be applied either prior to, at, or immediately after transplanting.

Repeat applications may improve efficacy of biological control agents.

No single product has been shown to give complete control, although thiram as a seed treatment, azoxystrobin, fosetyl-aluminium, and fluopyram + trifloxystrobin as foliar sprays and three biofungicides (Trianum-P, T34 Biocontrol and Prestop) have shown promise in different trials.

SCEPTREplus will conduct a trial in 2018 to investigate the efficacy of new and alternative biological and chemical control options for FOL, considering mode and timing of applications.

Parker added, “The limited control options stress how vital good hygiene practises are to prevent disease infection. These need to be implemented before any symptoms are seen; it is important that the industry acts now.”

The full technical report is available to read at horticulture.ahdb.org.uk/ lettuce-fusarium-wilt-and-root-rot

ACTIONS FOR GROWERS No single measure will result in complete control, rather using a range of disease management approaches offers the best chance to manage the disease. Growers should consider the following recommendations: HYGIENE ●● ●● ●● ●●

Limit the number of visitors to production areas Ensure all visitors follow hygiene procedures Overshoes should be worn to prevent spread Remove soil from plant trays, pallets and equipment before treating with disinfectants ●● Dispose of any infected plants and surrounding soil and consider soil disinfestation for whole cropping areas

MONITORING

●● C heck lettuce plants for symptoms regularly and cut open suspect plants to look for vascular browning ●● Send intact plant samples with suspect wilt symptoms to Andrew Taylor, University of Warwick, to check for FOL and confirm that it is race 4

CULTURAL CONTROL ●● ●● ●● ●●

Reduce the intensity of cropping Introduce rotation crops such as pak choi Avoid growing lettuce in warmest summer months Minimise plant stress, e.g. nutrient imbalance, herbicide damage, drought or soil compaction ●● Leave soil fallow and remove all weeds ●● Remove all loose plant material from glasshouses and use a propane burner to eliminate remaining material on the soil surface

SOIL TREATMENTS

●● Disinfest soil using steam or the application of Basamid

YMPTOMS TO LOOK S OUT FOR

Lettuce Fusarium wilt causes stunting and yellowing, ultimately leading to plant death. If you suspect FOL, cut the plant down the middle; a key characteristic symptom of the disease is a brown/black/red discolouration of the vascular tissue of the stem or taproot.

Early diagnosis is critical for limiting the spread. If symptoms are observed, send plant samples (with roots attached) to Andrew Taylor, Warwick Crop Centre, University of Warwick, Wellesbourne, Warwick, CV35 9EF. FOL4 cannot currently be accurately diagnosed from soil samples.

Hygiene measures are therefore crucial to prevent the spread of the disease

Project leader: Dr Andrew Taylor, University of Warwick AHDB contact: Kim Parker

Apr/May 2018 9

BEYOND THE HORIZON

With a year remaining before the all-important Brexit date, Haroon Jabar asks AHDB International Market Development Director Phil Hadley and AHDB Horticulture Strategy Director Steve Tones to weigh up the challenges and opportunities for Britain’s Horticulture enterprises

Phil Hadley, International Market Development Director, AHDB Horticulture phil.hadley@ahdb.org.uk Q: CAN YOU SET THE SCENE ON THE KEY CONCERNS FACING THE HORTICULTURE INDUSTRY TODAY?

Steve Tones: UK growers have driven up productivity of all horticultural crops hugely over the last fifty years through a combination of technical innovation, major restructuring and consolidation of businesses and supply chains.

All of this has been possible only because the industry has been able to draw on effectively affordable, capable and motivated seasonal labour from various Eastern member states of the EU. A reduction in the availability of this labour is the most immediate threat posed by Brexit.

Growers are themselves already responding to this threat by offering improved rates of pay and working conditions. However, if reliable alternative sources of labour are not secured in the near future, the only option available to UK growers will be to export their production overseas to places where skilled labour is readily obtainable.

Automation and robotic technologies offer promising long-term alternatives to human labour for many activities, but even the most advanced of these will probably not be commercially available for some years. However, for those businesses that are able to weather the short-term storm through innovation or adaptation of one kind or another, the long-term future will almost certainly offer tremendous opportunities.

Q: IN WHAT AREAS DO YOU SEE OPPORTUNITIES FOR THE UK’S FRESH PRODUCE INDUSTRY POSTBREXIT?

Phil Hadley: The UK is a net importer and if there’s an imposition of tariffs or additional costs, this could create opportunities for import displacement for 10 AHDB Grower IN FOCUS

UK-based growers. That might also result in an uplift in retail price, which would be challenging in the marketplace.

If import prices rise, there will potentially be gaps for some companies to grow more fresh produce, but the challenges will be limited land, investment and the ability to get enough labour to deal with a potential rise in production.

Steve Tones: The main opportunity for UK produce lies in import displacement.

The government might usefully support this through the industrial strategy and by other means. Horticultural productivity is almost completely reliant on effective crop protection measures.

A highly responsive regulatory system is therefore needed to ensure that growers are able to access new environmentally safe pesticides and biopesticides as soon as they become available.

Q: HOW CAN COMPANIES MAKE THE MOST OF BREXIT? Phil Hadley: Introduced tariffs and changes in the value of Sterling against other currencies will affect the relative price of exported and imported produce and materials in different ways, which may strengthen the competitiveness of British produce in some situations and weaken it in others.

Businesses that plan ahead and put themselves in a position to manage these risks and respond to market opportunities will be the ones most likely to thrive and prosper. But there are no certainties. Things will be tough for many. Even if there is an increase in the demand for British produce, growers who could respond may lack the capacity, resources or confidence to do so.

Steve Tones, Strategy Director, AHDB Horticulture steve.tones@ahdb.org.uk

Q: DO YOU SEE CHANCES FOR UK COMPANIES TO REACH NEW MARKETS?

Phil Hadley: Opportunities lie in targeting key markets where particular products are in demand. Some of the businesses that currently export to EU markets may find there are alternative markets that they’ve not dealt with before which become attractive if the EU market comes under pressure. There’s no doubt that other businesses in the EU and further afield are also looking at the UK as both a threat and an opportunity.

Steve Tones: The markets in which the greatest import displacement opportunities lie include those for berry fruits, apples, beans, nuts, cut flowers and ornamental plants, and the various added value food, drink and entertainment products made from these things. Markets may also develop for novel crops not currently produced in significant volumes.

Q: WHAT WOULD BE THE MOST BENEFICIAL GOVERNMENT APPROACH TO BREXIT IN TERMS OF TRADE, SUPPORT PAYMENTS AND SEASONAL LABOUR? Steve Tones: UK growers already compete successfully with overseas suppliers in the UK produce marketplace, but to do so depends on freely available and affordable skilled seasonal labour. Until robotic alternatives to human labour have been developed and introduced, retaining access to such labour remains crucial to the viability of UK horticultural production.

IN FOCUS

Government soft loans or grants to accelerate the development and uptake of automation and robotics technologies

by UK growers would have a welcome accelerating effect on such innovations.

Q: AS A REPRESENTATIVE OF BRITAIN’S FRESH PRODUCE INDUSTRY, WHAT WOULD YOU MOST LIKE TO SEE COME OUT OF THE BREXIT NEGOTIATIONS?

Phil Hadley: Trading arrangements around volumes, tariffs, access to market and the level of bureaucracy associated with moving products should not unduly hinder trade or create additional cost or time delays. With short shelf-life products, you can’t easily cope with an increase in shipping delays.

If the value of Sterling is weak relative to the Euro, it will reduce the value of money EU workers receive when converted into euros, so wages may need to be increased to attract them to the UK. One option would be for companies to source workers from further afield that are less subject to these EU currency variations.

Q: DO YOU HAVE CONCERNS THAT THE LEVEL OF QUALITY AND ENVIRONMENTAL STANDARDS MAY BE REDUCED WHEN BRITAIN LEAVES THE EU? Phil Hadley: The government has made it clear it is committed to exceptionally high standards for domestic products, particularly when it comes to the environment. When it comes to imports, it is equally important we don’t create an uneven playing field and avoid a race to the bottom.

Steve Tones: In light of the competition between them, the retailers seem unlikely to permit a significant reduction in the quality or environmental standards of produce offered to their customers, whose expectations are already well established.

There’s no doubt that other businesses in the EU and further afield are also looking at the UK as both a threat and an opportunity Phil Hadley, AHDB The chief negotiators: The UK’s David Davis (left) and the EU’s Michel Barnier (right)

Apr/May 2018 11

THE ART OF MAKING SOME GREEN New varieties could hold the key to significant financial gains for vining pea growers.

Stephen Belcher, PGRO, reveals some of the leading contenders

To the layperson peas either come in cans or frozen packs, are green and round, and are a somewhat tricky challenge to pick up on a fork – and that’s often about as far as their thinking on the subject goes.

To the grower, however, the production of this delicious vegetable is a much more complex operation.

Vining peas have a vital requirement to be harvested at a precise crop maturity, which means planning for a successful harvest requires great experience from those concerned; and variety choice is one key element of this complex science.

So, with the vining pea industry having a farm gate value of around £52 million per annum, and an estimated retail value of £500 million per year, improvements of just 5% in yield and quality could net the industry an impressive £2.6 million extra at the farm gate each year.

AHDB project FV 340b is an extension of project ‘FV 340: Vining pea trials’ and hopes to be able to help deliver these financial benefits for vining pea growers.

In order to achieve this a number of varieties have been tested against one of the industry standard varieties, Avola, to ascertain changes growers could make to increase the profitability of their crop (the other standards being Bikini and Ambassador).

However, it is not quite as simple as picking a wellperforming variety from a trial, as vining peas are grown on many different soil types, each giving potentially different results for each variety. To that end, AHDB has funded a series of variety trials grown on a light silt soil type in the south of Lincolnshire (near Holbeach). A separate descriptive list is now produced for this area and soil type and currently describes 52 varieties, with a range of leaf types, and maturities ranging from -1 to +15 maturity days compared to the standard Avola.

Stephen Belcher, PGRO All of the varieties trialled represent improvements in yield, size-grade, colour, uniformity and/or disease tolerance compared to Avola, all of which are criteria that should benefit the grower when it comes to maximising payment from processors and retailers.

TRIED AND TESTED

While there were many results from the trials, the varieties Beverly and Tomahawk showed considerable promise for growers. The former, with a maturity of -1, is now the earliest maturing on the list. The latter, Tomahawk, has out-yielded the early standards. Another such example of a successfully trialled variety was Maurice, which has out-yielded Oasis at TR100 (see ‘What is a Tenderometer?’ for more on TR ratings) and has good field resistance to downy mildew (Peronospora viciae). Also late maturing and out-yielding Oasis were Reflection and CS-445AF. In a previous year’s trial, Sherwood, an early maturing replacement for Avola, matured at the same time as Avola while giving a significant yield increase at TR100.

Improvements of just 5% in yield and quality could net the industry £2.6 million extra

AHDB project code: FV 340b Project leader: Steve Belcher, PGRO AHDB contact: Dawn Teverson 12 AHDB Grower CULTIVATE

CULTIVATE

THE BATTLE AGAINST DOWNY MILDEW

Currently downy mildew in peas is mainly controlled by the use of Wakil XL seed treatment, crop rotation (one year in five) and use of disease tolerant varieties in areas of high disease pressure. However there are reports that some varieties do not perform well in all pea growing areas due to the presence of different races of downy mildew. AHDB project FV 436, which is being undertaken by Lea Herold, PGRO, is studying the effects of different races of downy mildew on pea varieties, further details of which can be found on AHDB’s website.

At a time when restrictions have been placed on the use of seed treatments to control downy mildew, the use of varieties with a high tolerance to the disease will be more important.

The varieties Saltingo, D165618, Fantastigo and D856607 also completed trials in 2017 in project FV 340b and, encouragingly, showed good field resistance to downy mildew.

At its core, project FV 340b is designed to provide vining pea growers with independent, relevant and accurate evaluations of vining pea varieties so that a considered and informed variety choice can be made. Richard Fitzpatrick, General Manager at HMC Peas in Spalding, Lincolnshire, explained the benefit of AHDB’s work to growers, saying, “This is an extremely worthwhile project as it allows growers to choose new varieties based on quality independent research.

It demonstrates the strengths and weaknesses of new varieties in a climate of less reliance on pesticides and more emphasis on plant disease resistance and vigour. In times where we are experiencing more extreme weather events we also need to find varieties that are more able to withstand these extremes. The vining pea crop is an important part of the crop rotation, but it needs to remain financially viable, therefore it is vital that we have independent variety trial data.”

FURTHER RESEARCH

Further details are included in the AHDB-funded publication ‘Vining Pea Variety Guide’ - which contains details of varieties completing trials between 2008 and 2017 – and can downloaded for free from the AHDB website horticulture.ahdb.org.uk/publications

WHAT IS A TENDEROMETER?

A Tenderometer is used by most pea processors to pay their growers based on the Tenderometer value of the peas delivered to the processing plant. In essence, a Tenderometer is a machine that measures the force required to crush a sample of peas through a press, giving a reading in Tenderometer units. A Tenderometer Unit is a direct measure of the maturity and quality of the raw product being supplied, analysed in bulk, and it is from this that the quality of peas is graded.

Apr/May 2018 13

BUZZED OFF

Not all tomato growers have been entirely pleased with the enforced change from non-native bumblebee species to the native Bombus terretris audax. Independent IPM consultant, Rob Jacobson, examines their concerns in more detail Bumblebees were first introduced to British tomato growers in 1989 via trials on the Isle of Wight. The benefits, in terms of reduced labour and improved fruit set, were so great that by 1992 bumblebees were being used to pollinate virtually all long-season tomato crops in the UK. There followed revisions to hive design but biological pollination was so reliable that growers came to expect perfect fruit set with minimal maintenance.

In the 1980s, three commercial bumblebee producers tested many populations of Bombus terrestris to determine which provided the best results in tomato crops. They independently selected two non-native sub-species; B. terrestris terrestris (Btt) and B. terrestris dalmatinus (Btd); the British native subspecies, B. terrestris audax (Bta) was dismissed due to inferior performance.

CHANGE BRINGS CHALLENGE

However, in 2014, Natural England produced a document which suggested that non-native bumblebees could hybridise with wild Bta, leading to the local extinction of Bta. Following an open consultation, Natural England revised its policy, and permission to use non-native bumblebees in unscreened glasshouses was withdrawn from 31 December 2014.

Commercially-reared native Bta could still be used without a license.

development or ambient conditions be sub-optimal for their performance.

No growers considered the performance of Bta to have surpassed Btt/Btd, but 34% believed that their performance was similar - albeit with many more Bta hives being used. However, 28% of growers said Bta were poorer, 28% much poorer and 9% very much poorer than Btt/Btd. In fact, one grower estimated that poor fruit set cost his business £50,000/ha in 2015. In addition, reduced confidence in bumblebees led to 75% of growers devoting more labour to monitoring fruit set, at additional cost to their businesses.

Planned Bta hive input schedules varied greatly between suppliers, sites, tomato types and growing season length. Many growers said they required additional hives to those included in the planned schedule, with 28% occasionally ordering extra Bta hives and 69% saying this was a frequent requirement.

Interestingly, 47% of growers thought Bta colony life was considerably shorter than they had come to expect from non-native bumblebees. Shorter than anticipated colony life could result in gaps in the planned schedule, causing a breakdown in the continuity of bumblebee activity which might explain why so many additional Bta hives were ordered.

The use of Bta in 2015 proved to be far from the reliable and maintenancefree experience to which growers had become accustomed. In fact, several growers suffered such poor results that they reverted to labour-intensive manual methods of pollination not required since bumblebees were first introduced in the 1980s. The British Tomato Growers’ Association’s Technical Committee organised an in-depth survey, funded by AHDB, of tomato growers to gather more information about the current situation.

Growers representing 98% of the UK tomato production area participated.

14 AHDB Grower CULTIVATE

Growers reported improved results when they changed from fortnightly to weekly hive deliveries Four growers reported improved results when they changed from fortnightly to weekly hive deliveries, which was thought to reduce peaks and troughs in bumblebee activity.

One-third of growers said their staff had asked “Where are the bees?” at some point during the season. This related to the apparent lack of Bta activity during working hours. One grower believed that this was because Bta foraged early in the morning and their activity was underestimated. If correct, then Bta activity may be poorly synchronised to pollen release in tomato flowers; this theory requires further investigation.

All types of tomato are affected by poor set but problems are most serious in smaller fruiting cultivars which produce more flowers. One grower, who reported a reduction in bumblebee efficacy since the switch to Bta, also reported a move to small fruiting cultivars during the same period.

This was typical of an overall UK trend.

In 2011, only 28.8% of UK tomato production was of the cherry/cocktail type but by 2016 (i.e. post Bta) it had increased to 76.9%. This is clearly an important factor.

AN ALTERNATIVE CULPRIT?

MOUNTING COSTS

The clearest overall message from British tomato growers was the general belief that Bta are less ‘vigorous’ than previously used non-native sub-species and more likely to fail to provide adequate pollination should any aspect of flower

Rob Jacobson, Rob Jacobson Consultancy

Only 12% of growers considered that the condition of plants could be the underlying cause of poor set experienced on their sites. Nonetheless, there is a strong belief among some respondents that vegetative, rather than generative, tomato An example of missed set in tomatoes

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plant growth results in weaker flowers and poorer set. One grower thought that current crop husbandry practice led to poor pollen quality in modern tomato cultivars. In his opinion, if plants are strong and generative, thenpollen flows freely and may not even need disturbance by bumblebees to pollinate. Another grower said that pollen did not flow freely in humid conditions and speculated that Btt/Btd could cope with this but Bta could not. In fact, very little research has been published on flowering and fruit set in tomato since the late 1980s when bumblebees were first introduced.

MOVING FORWARD

“The survey work has already indicated that there are significant issues regarding tomato crop pollination using the newly introduced native sub-species of bumblebees,” revealed Paul Faulkner, from tomato grower Eric Wall Ltd., adding; “this project is an excellent example of the Tomato Grower Association Technical Committee working with the best British researchers and AHDB, reacting quickly to emerging issues in order to minimise the economic impact of such issues to producers while potentially returning many times the cost of the research, even within the lifetime of the project.”

Phase two of the work, project PE 031a, began in January and will look to build upon the findings from PE 031, with an end goal of establishing a foundation upon which to build a practical research programme to address some of the issues raised in the survey, such as: ●● Bta biology and behaviour under different environmental conditions with particular emphasis on synchrony between bumblebee foraging and optimum pollen flow ●● Bta colony life in greenhouses and the associated impact on hive input schedules ●● The influence of environmental conditions on flower quality and pollen flow in small fruiting cultivars ●● Changes in bumblebee usage and agronomic practice required to optimise pollination and fruit set

Some suffered such poor results that they reverted to labour-intensive manual methods of pollination not required since the 1980s AHDB project code: PE 031 Project leader: Rob Jacobson, Rob Jacobson Consultancy AHDB contact: Nikki Harrison

Apr/May 2018 15

PRODUCING PERFECT PRODUCE BY PARTHENOCARPY Can the traditional methods of pollination in cucurbits be bypassed to create perfect produce via parthenocarpy? Jessica Knapp, University of Exeter, investigates

It is no secret that, like most plants that produce a fruit, Cucurbit crops generally require pollination from insects for their fruit to be large and well formed.

However, the process requires co-operation from the insects and sometimes considerable work from the grower to ensure that each plant achieves the pollination required.

So, if there was an ‘easier’ way to ensure cucurbits achieved marketable size then it would be a significant boost to growers everywhere in terms of savings on pollinators and labour.

This is where ‘parthenocarpy’– the term used for fruit set in the absence of fertilisation – becomes of interest because of its potential to help cucurbits to reach maturity via the use of selective breeding.

AHDB project ‘CP 118 Cucurbit pollination: mechanisms and management to optimise field crop quality and quantity’ set out to investigate if pollination is limiting to fruit quality and quantity, and if so, under what environmental conditions, in courgettes (variant: Tosca).

Initial findings showed that while pollination increases the size, weight, and growth rate of courgettes, natural parthenocarpy means that many fruits were able to reach marketable size and shape without any pollination at all.

Results of a literature review showed that all techniques to induce parthenocarpy (selective breeding, hormone application, or genetic modification) were able to increase fruit quantity without adversely affecting quality in 18 pollinatordependent crop species (not including seed and nut crops as parthenocarpy causes seedlessness) which traditionally require pollination for fruit set.

Despite the natural parthenocarpic tendency of courgette, no selectively-bred parthenocarpic varieties are currently grown at a commercial scale in the United Kingdom. Pollination experiments show that 41% of fruit set is still dependent on natural pollination, with percentage fruit set, the size and weight, but not sugar content, of courgettes being significantly increased with pollination.

Fortunately, at most of the study sites the pollination rates were so high that there was no statistical difference in the yield of hand (artificial) and open-pollinated (insect pollinated) fruits. This may explain why, when commercial bumblebee colonies were introduced, there was no difference in yield (percentage fruit set, weight, or length) between fields with or without colonies.

Of course, pollination is entirely dependent on the availability of pollinators and suitable habitat to sustain their populations.

Therefore, the high level of pollination observed in this study is likely to vary between courgette-growing regions. For example, our study across different sites in the UK showed that more wild flowers in field margins resulted in more pollinators in courgette fields. Therefore, allowing uncultivated areas around the crop to be colonised by wild flowers could be an effective way of boosting pollinator visitation, which in turn may increase yield.

Since the total economic value of insect pollination to courgette is estimated to be worth £2.7 million in the UK (£3,400 per hectare), growers may wish to preserve their wild flowers on the edge of fields as a way of mitigating potential fluctuations in pollinator populations and yield. In doing so, they may also enhance other ecosystem services vital for agricultural production, such as natural pest control.

Since a crop’s need for pollination could be greatly reduced, parthenocarpy could allow producers to extend their growing seasons to exploit environmental conditions usually adverse for pollinators, furthering their economic advantage, increasing agricultural resilience, and improving food security.

Many fruits were able to reach marketable size and shape without any pollination 16 AHDB Grower CULTIVATE

AHDB project code: CP 118 Project lead: Jessica Knapp, University of Exeter AHDB contact: Grace Choto

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EAMU LATEST

Bolette Palle Neve, Crop Protection Scientist, AHDB bolette.palle-neve@ahdb.org.uk

BRIDGING THE DATA GAP Getting plant protection products approved for minor crops is always a challenge but even more so for the ornamentals sector. In the past few years we have been working with CRD to improve the success rate for ornamental approvals. The first step in the right direction was when CRD approved single-use splash resistant gloves as a mitigating factor for workers entering crops which had been treated. We have since seen a number of EAMUs come through with a requirement for workers to wear gloves. These approvals would have been refused in the past.

One of the problems with conducting risk assessments for ornamental crops is the significant lack of data to support use in this sector. This means that it is difficult for CRD to assess the actual risk of applying plant protection products in ornamental crops.

For a while we had problems obtaining approvals due to the perceived risk to the environment. However, it became apparent that a crop interception value of 0% was being assumed for these risk assessments –

EAMUS IN FOCUS Terpal (ethephon + mepiquat chloride)

basically assuming that 100% of the product would end up on the soil or growing media.

Plant protection products are expensive and growers would never apply a product where 100% would end up on the soil unless in the case of pre-emergence herbicides or other soil treatments. Through discussion and clarification with the CRD, this concern has now been resolved, and has resulted in successful authorisations.

To further help obtain additional approvals for ornamentals we are currently discussing new approval categories for ornamentals with CRD. The hope is that if we split the current group ‘ornamental plant production’ the risk assessments can become more targeted and hopefully lead to more successful EAMU applications. The approval groups we’re currently looking at are: pot plant and bedding plant production, container-grown HNS production, field-grown HNS production, and cut flower production. These proposed groups will be discussed further with our ornamentals panels and CRD over the next few months.

“In recent years, as new approvals and EAMUs for PGRs have been issued we have seen an increasing number of restrictions applied to their use.

For example, chlormequat is now only approved for use on protected ornamentals as a single product, Stabilan 750 (EAMUs 1416/17 and 0910/17), at a lower rate and with fewer applications permitted than in the previous EAMU. Chlormequat products have historically been widely used, but particularly on pelargonium and osteospermum, where early application improves plant structure as it promotes lateral branching, and it is the industry standard for poinsettia production,” explained Jill England, ADAS, adding; “Terpal is, in principle,

a good alternative to chlormequat. The formulation includes both mepiquat chloride and ethephon. The former belongs to the same chemical group as chlormequat (quaternary ammonium compounds, QACs) and should perform in a similar manner, and the latter breaks down within the plant to ethylene; both can promote lateral branching. Terpal applied as a spray performed well in Bedding and Pot Plant Centre trials in 2017, both on bedding and pot plants, including poinsettia, but the drench rates used were too strong. Further work planned for 2018 will determine appropriate rates for sprays and drenches on a range of bedding, pot plants and poinsettia.”

To discover all of the latest EAMUs visit horticulture.ahdb.org.uk/eamu-news Apr/May 2018 17

BIOPESTICIDES – YOUR QUESTIONS In the final part of our series on biopesticides, Warwick Crop Centre’s Dave Chandler answers some of your questions on all aspects of biopesticides, from usage to regulatory queries

Q: IS THE APPROVALS PROCESS FOR BIOPESTICIDES AND CONVENTIONALS THE SAME?

All plant protection products need approval at both EU and national level before they can be sold for use. The basic procedure is the same for all products, but the data requirements for biopesticides are less than those for conventionals to reflect the fact that they are less hazardous. A new system has just been put into place designed to fast-track the approvals of pheromones and microbes because these are known to be minimal risk products.

Q: WHAT IS THE CORRECT WAY TO STORE A BIOPESTICIDE AND HOW DO I FIND THIS INFORMATION?

The information you need is on the label and most suppliers also produce detailed technical guidance notes that are important to read. Different biopesticides have different storage requirements.

It should be remembered that the microbial biopesticides are alive, so storing them in excessive temperature conditions (for example, at temperatures above 30oC, or below freezing) can be very harmful to them. For this reason most need to be kept under cool conditions and some should be stored in a refrigerator.

This brings us onto a related point – the need to understand the product, know how it works, and to have good training for all staff that are working with biopesticides. The term ‘biopesticides’ covers a wide range of entities, including living microbes, pheromones and other natural products. They all have their own mode of action and have particular requirements for storage, application, etc., that you need to understand in order to get the best out of them. Biopesticides are harder to use than conventional pesticides but there are distinct benefits in using them as part of IPM. In many respects we’re in a similar situation to when ‘macro’ biocontrol agents came onto the market; it took some time for growers to optimise the use of these biocontrols in their own growing systems, but they’ve proved to be really valuable.

Q: HOW IMPORTANT IS IT TO HAVE SEPARATE SPRAY EQUIPMENT FOR BIOPESTICIDES?

Conventional chemical pesticides can be harmful to microbial biopesticides. For example, some conventional fungicides will kill fungal-based biopesticides. Therefore you need to think about stopping direct contact between biopesticides and any chemicals that they are not compatible with. It’s clearly important to wash out all spray equipment after use to ensure that no residue is left.

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The standard recommendation is to triple rinse, but this can still leave residues behind, so we are trying to encourage growers to have separate spray tanks for chemical pesticides and microbial biopesticides.

Q: HOW DO I MAKE BIOPESTICIDES MORE RELIABLE?

Growers have been using biopesticides more and while they find some work very well, others can give variable results. This is not surprising as they are a new technology and it will take time to optimise their use. We are looking at ways to get the best out of biopesticides in the AHDB AMBER project. One of the most important things is to follow the best practice guidelines for the product. This is all about getting the basics right: store the product correctly, read the label and the technical guidance, and make sure you are applying the product properly. We are concerned that growers are not paying enough attention to good spray application; nozzles are not being checked and changed, even though this is cheap and quick to do, while spray equipment is not being cleaned out. Similarly few growers are calibrating their sprayers properly. Conventional pesticides can be fairly forgiving and so in the past growers may have gotten away with poor spray application, but this isn’t the case with biopesticides.

In AMBER we are also working to fill some of the gaps in knowledge about how biopesticides work on different pests, diseases and on different crop types. Our partners at Silsoe have done a lot around spray application issues. One of the things they are working on at the moment is optimising the spray volume.

In general, we think the water volumes being recommended for biopesticides are too high, with too much of the product being lost through run-off. We are also investigating how biopesticide performance is determined by the size and structure of pest populations. Some biopesticides work slower than conventionals, which impacts on their ability to control fast-growing pests with short lifecycles. However, the details of how pest lifecycle affects biopesticide performance is not well understood, so we’ve started to address this using a combination of computer modeling and experiments. Finally, we’re also investigating the persistence of biopesticides on the crop, as this is important for determining the optimal strategy in terms of the timing and frequency of application.

“From the AMBER project it’s clear that accurate application for biopesticides is a key area where growers can make some big differences, through simple changes prior to application, such as ensuring equipment is properly cleaned, calibrated and appropriate for the biopesticide that is being applied and following best practice guidelines,” explained Joe Martin, Crop Protection Senior Scientist at AHDB.

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Biopesticides all have particular requirements for storage and application that you need to understand to get the best out of them Q: HOW DO I INCORPORATE A BIOPESTICIDE INTO MY EXISTING IPM PROGRAMME?

Biopesticides are not like-for-like replacements for conventional pesticides, rather they are tools to be used as part of an IPM programme. The basic idea behind IPM is straightforward – combine different tools together in complementary ways, underpinned by careful monitoring of pests and their natural enemies. The challenge is to design and implement an IPM programme that meets the needs of your particular crop and growing system, and which is practical, cost effective and flexible enough to respond to things such as sudden changes in pest pressure. By understanding the strengths and weaknesses of individual biopesticide products you can then build them into IPM in a rational way that works for you.

An interesting example of this is the work that Rob Jacobson has done in protected edibles, using biopesticides as a supplementary treatment. In this system, biopesticides have been used as a back-up to preventative control using predators and parasitoids; if the pest population starts to outstrip the ability of the predators or parasitoids to control it, then applications of biopesticides can slow the pest growth down and allow the macro agents to get back on track. This system can work well for spider mite and western flower thrips control for example, and the supplementary treatment can make all the difference between success and failure in IPM. Where conventional pesticides are in use, biopesticides can be incorporated during periods when pest or disease pressure are lower, or close to harvest to take advantage of their short harvest interval.

Q: ARE THERE MORE BIOPESTICIDES THAT WILL BE AVAILABLE SOON?

There has been a year-on-year increase in the number of biopesticides becoming available in the UK, and as the market develops we expect to see many more arrive on the market.

To find out more about AHDB’s AMBER project, visit: bit.ly/AMBERproject

AHDB project code: CP 158 Project lead: Dave Chandler, University of Warwick AHDB contact: Joe Martin

Apr/May 2018 19

Vine weevil adults lay eggs at lower temperatures than previously thought, down to 6°C

KNOWING YOUR ENEMY

Jude Bennison, ADAS Entomologist, explains how current studies into the biology and behaviour of vine weevils could help to keep them under control Vine weevil is the main pest of containergrown hardy nursery stock and due to the withdrawal of, and restrictions on, using most longer-term incorporated plant protection products for control of larvae the battle is becoming increasingly more difficult. Therefore, a robust integrated pest management (IPM) strategy is needed, tackling both adults and larvae.

IMPROVING KNOWLEDGE ON VINE WEEVIL BIOLOGY AND BEHAVIOUR

In the first year of AHDB project ‘HNS 195 - Improving control of vine weevil on hardy nursery stock’, Tom Pope at Harper Adams University showed that vine weevil adults feed and lay eggs at lower temperatures than previously thought, down to 6°C. Last year, air temperature records from protected structures in West Sussex showed that temperatures were 6°C or above for at least one hour on most nights of the year. However, it is not known for how long temperatures need to exceed 6°C before egg laying recommences. Laboratory experiments in 2017 showed that overwintered adults need a five-week period of intense feeding before they recommence laying eggs.

This is problematic because the currently approved entomopathogenic fungus Metarhizium brunneum (anisopliae) (Met52 Granular Bioinsecticide) for control of vine weevil larvae needs warm temperatures (15-30°C) to be effective. The product is recommended to be used as part of an IPM programme (not the only method for vine weevil control) and is best used during potting in the spring, rather than in the autumn, when temperatures are more 20 AHDB Grower PROTECT

suited. Gill Prince and Dave Chandler at Warwick Crop Centre are looking at the potential of cold tolerant fungal strains for vine weevil control and have obtained 11 candidate strains from different parts of the world.

Current experiments are testing growth of the fungi on agar plates at a range of temperatures between 4°C and 40°C. Once completed, selected fungi will be used to test infection and kill of vine weevil larvae at different temperatures to assess if any would have the potential for development as a new biopesticide.

‘LITTLE AND OFTEN’

Various entomopathogenic nematode species and products are used by growers for control of vine weevil larvae. However, many growers regard their use as time consuming and costly as application using high volume drenches is very labourintensive. In year one of the project, ADAS experimentally tested a ‘little and often’ approach to nematode application through the overhead irrigation. Both 20% and 40% rates of Steinernema kraussei (Nemasy L) applied five times from June to October gave equal control of larvae on fuchsia compared to the industry standard of two full rate nematode drenches in September and October. Last year, ADAS repeated the experiment on four fuchsia varieties at a commercial hardy nursery stock nursery to validate the results.

This time Heterorhabditis bacteriophora (Nemasys H) was used for the June to September applications and the coldtolerant product Nemasys L in October.

The 40% rate applied five times through the irrigation gave equal control of larvae to two full rate drenches applied in September and October on all four fuchsia varieties and the 20% rate gave equal control on ‘Tom Thumb’ and ‘Riccartoni’.

The ‘little and often’ system can offer a cost-effective strategy that saves on labour time, but needs testing on a wider range of plants.

FUTURE WORK

The project continues for two more years and aims to provide growers with a robust IPM strategy for vine weevil control.

If you’re considering applying nematodes via overhead irrigation, make sure you watch our new video which provides more details on the procedure: horticulture.ahdb.org.uk/ videos

AHDB project code: HNS 195 Project leader: Jude Bennison, ADAS AHDB contact: Wayne Brough

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DEFYING PROBLEM WEEDS John Atwood, ADAS, reveals the promising new stars of the weed control world that may help secure the future for hardy nursery stock growers Like many horticulture sectors, the withdrawal and dwindling availability of effective herbicides over the previous decade is causing concerns about the lack of chemical options to manage weed problems in the future. For growers of hardy nursery stock, this has recently gathered pace with the loss of Ronstar Granules and Ronstar Liquid (oxadiazon) along with ever more onerous restrictions on the remaining authorised herbicides.

As this is a high priority area for growers, AHDB Horticulture has continued to build on earlier weed control projects by funding a five-year project, ‘HNS 198 - Improving weed control in hardy nursery stock’, that began in 2016 with the aim of developing new weed control treatments for container- and field-grown hardy nursery stock. Along the way there have been success stories, but also some disappointments where promising herbicides have failed regulatory hurdles.

BOOM AND BUST

Two residual herbicides, Sunfire (flufenacet) and Defy (prosulfocarb), and one selective contact graminicide, Centurion Max (clethodim), were chosen to test for efficacy on a range of common weeds of container production and for crop safety.

Sunfire and Defy were both effective for pre-emergence control of annual meadow grass. Defy, in addition, gave good control of American willowherb including early post-emergence activity, and Sunfire gave partial control of pearlwort. Unfortunately, both herbicides were ineffective against bittercress species, chickweeds and groundsel. Sunfire already has an EAMU for ornamental plant production, including use under protection, however its use will be limited to situations where grass weeds are anticipated. In this respect it could complement Flexidor (isoxaben) which does not control grasses. Defy would mainly be of value for American willowherb control as a complement to Flexidor.

However, it currently only has an EAMU permitting use pre-emergence of a crop, so a modification of the EAMU to enable use over dormant crops would be required. As a winter herbicide for container production it could be an alternative to Devrinol (latest product not currently authorised) should Devrinol not be granted an EAMU for use in ornamentals. However, Devrinol would be preferred as it has a more comprehensive weed control spectrum.

Sunfire was generally safe when applied after potting over 10 hardy nursery stock species. A few subjects (Buddleia,

Hydrangea and Weigela) suffered temporary scorch but the plants grew away from this within six weeks. Defy is not safe when applied over actively growing plants and will be tested over dormant stock shortly.

The loss of Aramo (tetraploxydim) as a selective contact grass control treatment for use over ornamental crops has been significant, particularly for field-grown crops, as it controls annual meadow grass unlike other graminicides. One possible alternative, Centurion Max, was tested for safety over 10 hardy nursery stock species.

Two subjects (Hydrangea and Spiraea) suffered temporary scorch, but plants grew away from this within six weeks. Centurion Max was effective in controlling annual meadow grass at a range of sizes from one true leaf up to 10 true leaves. It can currently be used on ornamental crops under LTAEU and an EAMU has been applied for.

Looking ahead, the project will investigate the opportunities for the recently granted EAMU for Logo (foramsulfuron + iodosulfuron-methyl-sodium), including for use as a growing season directed spray in field-grown trees where the spacing permits alleyway applications.

A few subjects suffered temporary scorch but they grew away from this within six weeks

AHDB project code:HNS 198 Project leader: John Atwood, ADAS AHDB contact: Wayne Brough Apr/May 2018 21

PLUGGING THE GAPS

With dwindling crop protection options, SCEPTREplus has been busy testing new and existing actives to find solutions to help UK growers remain resilient to pests, weeds and diseases; and the trials are already starting to deliver new products Trial results generated in the first year of SCEPTREplus, AHDB’s flagship crop protection programme, have so far identified a number of useful products.

Two of these AHDB has secured Extensions of Minor Use (EAMU) for and another product tested now has on-label approval, with a further four applications already in progress.

The seven herbicide trials primarily focused on replacing linuron, which will be withdrawn

by June 2018. A range of efficacy and crop selectivity trials were carried out on carrots and parsnips, herbs, sweetcorn, celery, outdoor cucurbits, rhubarb and narcissus.

In order to generate product approvals from the trials, the SCEPTREplus team first review all trial results and assess the need for further data generation for efficacy and crop selectivity. They also consider whether residue data needs to be generated or can be sourced following discussions with the product manufactures. At that point the AHDB Minor Use team will progress applications with CRD in order to enable growers to have access to products as quickly as possible.

The approval for ‘Dual Gold’ will help sweetcorn growers by providing a different mode of action for weed control and an additional option at pre-emergence, supporting resistance management strategies.

WEED CONTROL

Herbicide trials were some of the first to start in 2017 to fit with commercial production schedules and trials for rhubarb and narcissus continued throughout the winter.

22 AHDB Grower PROTECT

The trials identified over 31 useful actives, with two EAMUs already secured and further applications now in progress.

‘Centurion Max’ will benefit herb growers as Clethodim, the active ingredient, can be used to effectively control troublesome annual and perennial grasses, though growers are strongly advised to test a small area of crop prior to extensive use.

David Norman, Fresh Produce Consultancy and researcher for the celery herbicide trials, said, “The revocation of linuron puts the future of UK celery production at risk, so finding alternatives and quickly, is crucial, hence this SCEPTREplus trial was one of the first commissions.

“The trial has identified three possible new herbicides for celery, Aclonifen and two currently coded products, all of which could provide part of the answer for replacing linuron.”

Further work is required on cucurbits and pumpkins looking at the newer herbicides identified in year one.

PEST CONTROL

The first year pest control trials ranged from aphid control, using a model target approach, to specific targets including asparagus beetle, onion thrips on leeks, two spotted spider mite, western flower thrips (WFT) and spotted wing drosophila.

Trials for WFT control have identified three biopesticides that achieved good levels of control when used in combination with N. cucumeris, giving good compatibility when used in an IPM approach with macro-biologicals.

Azatin, a botanical biopesticide which is widely used in the Netherlands, was trialled under code but will now be available to UK growers with an on-label approval from April 2018.

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Botanigard WP, used in a tank mix with Majestik, has an existing approval so can now be adopted into growers’ IPM programmes.

The further coded biopesticide will be taken forward for regulatory approval.

From the trials reported so far on onion thrip control in leeks, two insecticide treatments were identified to reduce thrip damage in leeks.

The two spotted spider mite in tomatoes trial identified four new products that gave significant reductions in pest numbers with potential for inclusion in IPM programmes.

The replicates tested in asparagus beetle trials so far indicate that seven of the 10 new products kill over 50% of the larvae within one day, and all of them have a considerable effect four days after treatment.

The aphid work in year one focused on willow-carrot aphid (Cavariella aegopodii) on carrots, currant-lettuce aphid (Nasonovia ribisnigri) on lettuce, peach potato aphid (Myzus persicae – Rothamsted P clone) on Brassicas and

cabbage aphid (Brevicoryne brassicae) on brassicas. In year two it will expand to look at other species not tested, including aphid control in peppers. Work on Tuta absoluta and aphid control in peppers is due to start in 2018.

However, one of the conventional pesticides and one biopesticide significantly reduced the stem-based lesions associated with this disease.

DISEASE CONTROL

SECOND YEAR TRIAL PLANS

Disease trials in 2017 included botrytis control in stored cabbage, bacterial canker in cherry, Pythium aphanidermatum in cucumber and downy mildew on lettuce as a model crop.

Although one product caused significant levels of phytotoxicity in the downy mildew trials, other products, including a biological product and a number of conventional products, gave significant levels of control.

Both disease trials provided useful data which can be taken forward.

Work in year two will continue to expand the understanding of the products tested in the first year trials, including further efficacy and crop selectivity assessments.

Where a model crop approach was used, as with downy mildew, a broad spectrum of crops will be further tested.

As well as continuing to investigate and expand upon the crop protection solutions from the first year, an additional 15 crop or target priorities have been identified and shortlisted.

With the initial model crop trial completed, promising treatments for downy mildew control on other crop species will follow within the SCEPTREplus programme.

Different treatments in the cucumber root rot (Pythium aphanidermatum) trial had negative impacts on the crop including reduced root development, wilting, reduced growth and yield.

Full details of the second year trials are available at horticulture.ahdb.org.uk/ SCEPTREplus.

The reports for first year trials will also be made available on the website.

Table: Number of new products tested and identified in pest, weed & disease trials in first year trials for SCEPTREplus Crop or target

Weed control*

Pest control

Disease control

New treatments tested

Useful treatments identified Conventional treatments 8

Biological treatments -

Carrots and parsnips

16

Herbs

6

5

-

Sweetcorn

21

6

-

Celery

10

3

-

Outdoor cucurbits

17

4

-

Rhubarb

16

6**

-

Onion thrip/leek

10

2

0

Western flower thrip/ornamentals

5

0

3

Two spotted spider mite/tomatoes

5

3

2

Downy mildew, Bremia lactucae/ protected lettuce

8

5

1

Pythium root rot, Pythium aphanidermatum/cucumber

6

1

1

*Narcissus and winter rhubarb trial data still being analysed **From summer trial

The trials identified over 31 useful actives, with two EAMUs already secured and further applications now in progress

SCEPTREPLUS Apr/May 2018 23

STAYING AHEAD OF XYLELLA’S SPREAD

Could the emergence and spread of the bacterial pathogen Xylella be a potential worldwide threat to horticulture? AHDB’s Wayne Brough investigates the measures being put in place to try to avoid an outbreak in the UK

While by no means a new pathogen, Xylella fastidiosa has seen a rapid spread across Europe in recent years having previously been confined to the Americas, giving rise to a range of diseases such as citrus variegated chlorosis in South America. In 2013 the pathogen was reported in olive trees in Italy. In 2015 France experienced a major outbreak in Polygala myrtifolia, while Spain reported an outbreak in cherry in 2016, and in a variety of other plants such as almond, olive and acacia in 2017. Other odd outbreaks on imported plant material across Europe have also been recorded which were subsequently quickly eradicated.

Xylella fastidiosa is a bacterial pathogen which affects the water conducting tissues of the plants it infects. A diverse species, it is subdivided into at least six subspecies (ssp.), but the three main subspecies include X. fastidiosa ssp. fastidiosa, ssp. pauca and ssp. multiplex, the latter being the main threat in the UK due to its climatic requirements.

Unlike many other bacterial diseases which are dispersed by water splash, X. fastidiosa is dispersed over short distances by a large range of sapfeeding insects. In the UK this will be via leafhoppers and froghoppers, of which there are at least ten common species. Long distance dispersal is via the movement of infected propagation and finished plant material either within countries or internationally.

One aspect which makes the pathogen so commercially important is the wide range of plants it can infect, with over 350 species from 75 families already identified as hosts.

24 AHDB Grower PROTECT

Lists of important commercial plant species have been circulated by Defra/APHA (see ‘Xylella fastidiosa: Implications for the nursery trade’ on the ww.gov.uk website) and are periodically updated. Symptoms include leaf scorch, chlorosis, wilt, poor quality fruit, dieback and eventually death, many of which can be confused with other disease or disorder symptoms.

Pathogen detection and identification of X. fastidiosa is currently based on DNA analysis techniques.

In 2015, the EU announced emergency measures to deal with the disease, which have been subsequently amended. On the discovery of an outbreak (as opposed to an interception) any host plants will be destroyed within a 100m radius and a five kilometre buffer zone will be imposed restricting the movement of specified plants for up to five years.

Anyone importing host plants from the EU needs to ensure that the plants are accompanied by a valid plant passport confirming they have been sourced from disease free areas and sites. From 1 March 2018, there will be additional measures for high risk hosts, including annual inspections of production sites, plant sampling and testing prior to plant movement, and the requirement to hold records for three years.

LATEST THINKING ON THE PATHOGEN In November 2017, a European Conference was held in Palma de Mallorca, Spain, to find an answer to the global problem. The three-day conference brought together the world’s leading authorities on the disease to exchange information on the biology,

identification, spread, detection and control of the pathogen. Highlighted below are some of the more relevant and interesting developments from the range of presentations undertaken by the speakers: A review of potential insect vectors in the UK identified 18 species in four families. In Europe only the meadow spittle bug is confirmed to be a vector of the pathogen. It is very common and widespread in the UK and polyphagus, feeding on 100-plus, mainly herbaceous plant hosts, but it can move onto trees in late summer in dry years. The majority of the other potential insect vectors in the UK are commonly recorded in grasslands and marshes, and are therefore less likely to be found near commercial nurseries thereby posing less of a risk as a vector.

Research has been carried out in Bari, Italy, to examine the control of the meadow spittle bug in olive plantations with a range of conventional insecticides, bioinsecticides and other substances. Neonicotinoid and pyrethroid insecticides were found to have the highest efficacy against juvenile stages and adult populations.

An assassin bug was also assessed as a potential biocontrol for the vector by other researchers in Italy.

The development of synthetic antibacterial peptides to inhibit bacterial development and induce plant defence against the pathogen was also reported.

Other research on potential control measures has examined the natural bacteria in olive sapwood. Under field conditions, the population level of cultivable ‘endophytic’ bacteria in

PROTECT

the sapwood is highly variable, but bacteria in the genus Methylobacterium occupy the same ecological niche as X. fastidiosa ssp. pauca and may have potential as a biocontrol, but further studies are required.

Work is ongoing to both develop efficient sampling procedures for the early detection of the pathogen in plants which are free of disease symptoms and to evaluate new diagnostic methods for use in both the laboratory and field, the latter includes the use of thermal imaging methods.

Molecular and classical breeding techniques have been used to develop resistance in grapes in California while maintaining grape quality, and olive varieties are currently being screened for potential resistance traits. This could be a long-term control measure

for some of the more important crops grown either in larger numbers or over wider areas.

Physiological aspects are also being evaluated and investigations initially indicate that calcium could play an important role in modulating the virulence of the pathogen.

Work on the basic biology of the pathogen including the identification of signalling factors which control the form of the bacteria in the plant (motile cells to move and proliferate the pathogen and sticky cells which form a biofilm and are responsible for vessel blockage in the plant and insect acquisition) and how this may be influenced by the chemistry of the plant sap is still ongoing, but could reveal potential elements of the bacteria’s lifecycle to focus on to develop new methods of control.

THE FUTURE

Reports from countries in which the pathogen is endemic or recently established appear to indicate that no single approach is sufficient to control the pathogen, and that an holistic approach including the use of clean plant material, appropriate cultural practices, efficient but environmentally friendly vector control coupled with efficient monitoring practices, are all needed to manage the pathogen and minimise its impact on commercial crops. Making sure the disease does not get into the UK is therefore the most cost effective way of currently managing the pathogen, but with the current level of international plant trade, procedures need to be developed for the inevitable day that the pathogen is confirmed.

One aspect which makes the pathogen so commercially important is the wide range of plants it can infect AHDB continue to review the latest research and are in contact with APHA to monitor developments. Up-to-date information can be found on our website at: horticulture.ahdb.org.uk/xylella-fastidiosa Pictured: A grapevine leaf displaying leaf scorch symptoms, due to a Xylella infection

Apr/May 2018 25

STAYING IN CONTROL Managing humidity is vital to ensuring greenhouse climate control, but it’s not as complex as many fear. Jon Swain, GrowSave, explains more

An important and often misunderstood aspect of greenhouse climate control is the issue of humidity. With its proliferation of terms and ideas, this subject can cause confusion and it was a topic of a recent GrowSave event, where growers assembled to get a reminder of the basics of humidity control.

GETTING CONTROL

Making sure that the greenhouse is in good condition and the measurements the computer makes are accurate is the first step towards good control. This includes ensuring that the structure is complete and any repairs are made quickly, having good and even heat distribution to be able to respond to the demand for heat, and checking that vents close completely and open together to well-defined positions.

Similarly, the key indications of humidity come from the measuring boxes, which need to be well-placed, in good condition and regularly checked and calibrated.

Most UK growers use relative humidity (RH) or humidity deficit (HD) as a lead control parameter. RH is an indicator of how much moisture is in the air as a percentage of saturation, with an RH of 100% describing fully saturated air. For small differences in temperature between plant and air, higher RH values lead to increased risk of condensation;

many growers aim to keep the RH below 80% to minimise this risk.

However, RH control is not good for driving transpiration and plant growth. Transpiration is driven by the ability of the plant to lose moisture through the stomata in the leaves and requires air capable of accepting moisture; this can be described by a concept called vapour pressure deficit.

The vapour pressure deficit (VPD) is measured in kPa and is the difference between the pressure of fully saturated air and the pressure of the water actually in the air. To keep an active plant, a VPD of >0.14kPa is required. Humidity deficit can be used as an approximation of VPD and is often a better-understood unit. HD tells us in g/m3 of air how much more water the air can hold; the higher the value, the drier the air and, therefore, the more active the transpiration of the plant. Typical HD values for plant growth are in the range of 2.5 – 6.0g/m3. A humidity deficit of zero means the air is fully saturated and will have an RH of 100%.

De-humidification is, more often than not, the greatest need

LEARN TO VENT

Manipulating humidity is often a function of changing the relative humidity. This is achieved by increasing or decreasing the greenhouse air temperature; warmer air can hold more moisture, so RH is decreased, even when the quantity of water in the air has not changed. To change the amount of water in the air, we either need to de-humidify or introduce water depending on what we are trying to achieve. De-humidification is, more often than not, the greatest need. We can achieve this relatively easily by replacing warmer, wetter air from inside with drier, cooler air from outside through venting.

The role of air movement in humidity control is becoming better recognised. Good air movement has two main benefits; the greenhouse climate is much more even, meaning that control is easier and more predictable and that plants grow more evenly. In addition, good air movement ensures the microclimate around the plants does not stagnate and the plant can remain active. Similarly, with good air movement, it is much more likely that microclimate conditions reflect the measurements made by the measuring boxes.

FOR MORE INFORMATION ON HOW YOU CAN MAKE ENERGY SAVINGS IN YOUR BUSINESS VISIT: HORTICULTURE.AHDB.ORG.UK/GROWSAVE

26 AHDB Grower RESOURCE MANAGEMENT

RESOURCE MANAGEMENT

TIME IS UP FOR TRICKLE EXEMPTIONS Defra and the Welsh Government are ending water abstraction licence exemptions in England and Wales. Nicola Dunn, AHDB, spells out the changes

The Environment Agency and Natural Resources Wales regulate water abstraction through a licensing system that has been in place since the 1960s.

However, certain abstractions have been exempt from licensing control because they were considered low risk or not widely used. This has meant that farmers using spray irrigation require an abstraction licence while those using trickle irrigation did not. The government consulted on bringing these exempt activities into the licensing system in 2009 and 2016.

THE CHANGES

Exemptions for all forms of irrigation (other than spray irrigation which is already licensable) and land drainage systems used in reverse to maintain field water levels will come to an end. Most new licences will be granted based on volumes typically used over the last seven years.

Licences will have conditions to protect the environment during low river flows. While licences will be issued with time limits, the government intends to phase out time limits as part of abstraction reform.

ENVIRONMENTAL PROTECTION

Hands off Flow (HoF) conditions will apply to some licences in order to protect the environment at low river flows and during drought conditions. HoF conditions will usually be applied in over-abstracted catchments when flow is at or below given thresholds and will prevent abstraction at those times.

COMPENSATION

It may be possible to claim compensation where loss or damage can be demonstrated as a result of being granted a licence for a lesser quantity, or if your licence is refused. The costs are recovered from other abstractors through the charges for their licences.

INCREASED VOLUMES

Any new or increased volume abstractions must go through the standard application process (where no compensation will be payable). There will be an aligned process to allow applications for previously exempt activities to be applied for, together with planned (variations to increase) abstractions.

NEXT STEPS

Changes to the exemptions came into force on 1 January 2018. Anyone currently operating under an exemption and abstracting more than 20m3/day will need to apply for a licence before 31 December 2019. Licences will be determined within three years from the end of the application window. Abstractors can continue to take their existing volumes during this process until a licence is granted, or until the application period closes if no application is made.

Evidence from the previous seven years of the historic abstraction will be needed to support applications, e.g. meter readings, pump ratings, calculations, invoices, photographs or receipts.

Guidance is available from the Environment Agency: www.gov.uk/guidance/apply-fora-new-abstraction-licence-for-a-currentlyexempt-abstraction and Natural Resources Wales: https://naturalresources.wales/ permits-and-permissions/waterabstraction-and-impoundment/ changes-to-water-abstraction-licensingexemptions/

ABSTRACTION REFORM These changes are occurring in parallel with other changes to the abstraction system taking place over the next five years. Government intends to introduce permits which will: ●● H ave volumes reflecting current business ●● A llow abstraction at any time when river flows are high

●● I ntroduce flow-based conditions to all permits affecting surface water ●● Allow easier water trading

●● R emove time limited licences and introduce a new risk-based catchment approach to permit reviews AHDB commissioned research in 2016 (project CP 159) to investigate the resilience of potato and horticulture businesses to changes in abstraction licensing. Key recommendations for growers were to: ●● Q uantify headroom and take account of this in business planning

●● C arry out economic assessments to understand benefits from improved water management

●● C onsider feasibility of investments in water storage, e.g. reservoirs ●● M aximise rainwater harvesting and grey water recycling ●● I mprove soil water retention through land management improvements

Anyone operating under an exemption and abstracting more than 20m3/day will need to apply for a licence Apr/May 2018 27

CROP VARIABILITY – IS THE ANSWER IN THE SOIL? AHDB’s GREATsoils programme has been looking at what growers can do to try to understand soil and crop variability on their farm. Lizzie Sagoo and Paul Newell Price, ADAS, share the findings so far

Consistency of crop size and quality are key issues for growers. However, withinfield variability in crop growth is usually apparent in most crops and fields. Soil variability is one of the main factors determining differences in crop growth within and between fields. Variations in soil texture, moisture holding capacity, organic matter content, nutrient content, drainage, compaction and soil depth are reflected in crop growth differences.

The challenge for growers, agronomists and researchers is to try to disentangle the various soil and other yield-limiting factors to understand which are most important in driving crop variability.

MAPPING VARIATION IN SOIL TYPE

A good starting point is to try to understand the underlying spatial variation in soil physical characteristics (soil type, slope and drainage). Many growers already have a good idea of how soils change across their fields and soil electrical conductivity (EC) scanning and satellite soil brightness imagery can be used to help identify soil variability as a basis for creating soil management zones within a field.

Soil EC surveys can help identify variation in soil texture, soil moisture and soil compaction. Satellite soil brightness maps describe how intensely the ground surface layer of bare soil reflects incoming sunlight and can be used as a combined indicator of variation in soil texture, organic matter content and soil moisture at the time the image was taken. Soil brightness imagery is affected by cultivations and stubble and it is worthwhile to ‘groundtruth’ the imagery.

It can be useful to compare soil EC or soil brightness maps with information on within-field variability in crop growth.

Soil EC maps have been shown to correlate well with crop growth because of the influence of soil texture on moisture holding capacity, organic matter content and nutrient availability.

WHAT ABOUT SOIL NITROGEN SUPPLY?

The growing crop is usually the best indicator of within-field variability in soil nitrogen (N) supply. Satellite imagery, tractor mounted sensors and UAVs (Unmanned aerial vehicles) can all be used to map the crop canopy and may be used as a basis for variable rate N fertiliser applications. The project demonstration on variable rate N at Glassford Hammond Farming showed a strong relationship between crop canopy measurements and N uptake in a Savoy Cabbage crop. However, variable rate N management will only be of benefit if nitrogen is the main cause of variability in crop growth – there are a number of other limiting factors that may also cause crop variability.

UNDERSTANDING CROP VARIABILITY

Understanding how soil and environmental limiting factors vary within a field and from year-to-year can help produce more consistent crop yield and quality. For each crop grown, look for consistent patterns of crop growth/ yields between years. Use yield maps (if available) for combinable crops and crop canopy maps for other crops.

Variation in crop yield and quality in any single year is due to a combination of

(i) interacting soil and weather factors, and (ii) more unpredictable variability in factors such as weed, pest and disease pressure. Even with good agronomy it can be very difficult to manage variable annual pressures on yield and quality, but it is useful to understand the pattern of more constant crop variation.

Sometimes the reason for yield variability may be clear, for example areas of lower soil pH. However, if the reason for the variability is not clear, consider targeted soil and crop sampling in contrasting high/low performing areas. In each area, dig out a block of soil, assess soil structure and rooting, and look for any evidence of soil compaction or poor drainage.

Take soil and leaf tissue samples for analysis of macro- and micro-nutrients.

Guidance on tissue sampling and interpretations of analysis results is given in AHDB’s Nutrient Management Guide (RB209).

Variable rate nitrogen management will only be of benefit if nitrogen is the main cause of variability in crop growth

GREATSOILS 28 AHDB Grower RESOURCE MANAGEMENT

RESOURCE MANAGEMENT

CASE STUDY: VARIABILITY IN LETTUCE HEAD WEIGHT In 2017 a case study at G’s Growers in Cambridgeshire sought to map and understand within-field variability in lettuce head weight. An Isaria tractor-mounted crop sensor was used to assess lettuce growth in a 30ha field.

The variability in crop growth identified by the Isaria corresponded well with the variation in soil organic matter content across the field. Soil samples taken on a regular one hectare grid from the field showed that soil organic matter varied from less than 10% in the southeast section of the field (corresponding to Willingham series silty clay loam soils) to greater than 35% in the northeast and southwest sections of the field (corresponding to Adventures’ series peat soils), and this pattern of variability can be seen in the satellite soil brightness map (with lighter areas corresponding to lower soil organic matter).

The Isaria crop canopy map was used to identify points of thinner and thicker crop within the different iceberg lettuce varieties in the field for targeted soil and tissue testing.

Within each of the varieties, where the crop was thinner, the soil organic matter content was also lower. However, soil and tissue macro- and micro-nutrient analysis were unable to identify a clear crop nutrition reason for these differences.

Soil moisture probes installed in the northeast and southeast sections of the field in areas of contrasting higher and lower soil organic matter content showed consistently higher soil

Isaria tractor mounted sensor

available water in the higher organic matter soil. Although the field was irrigated, it is possible that differences in soil moisture holding capacity related to organic matter content can partly explain the differences in crop growth across the field. Soil organic matter content was the main driver of crop growth variation within the field.

SUMMARY

Focussing on crop variability can help identify and address yield limiting factors. If the causes of yield variation can be identified and eliminated, the yields in the low yielding areas can potentially be increased resulting in ‘quick wins’ for all crops grown in the rotation. This approach is most effective for yield limiting factors, such as localised areas of low pH, that can be corrected by variable rate liming and areas of poor soil drainage that can be addressed to some extent by maintaining and repairing field drains.

However, remember that it may never be possible to eliminate the effect of soil variability on the crop, particularly in inherently variable fields. There is still some debate around whether it is better to manage this variability to produce an even crop across the field, or manage inputs to maximise yield potential in both high and low yielding areas, thereby accepting a degree of yield variability across the field.

Have you visited our website for more information?

Unearth a wealth of information on soil management at: horticulture.ahdb.org.uk/greatsoils

AHDB project code: CP 107c Project lead: Lizzie Sagoo & Paul Newell Price, ADAS AHDB contact: Jim Dimmock Isaria crop canopy map at G’s Growers – red areas indicate thinner crop

Apr/May 2018 29

THE PRODUCTIVITY PUZZLE With the news that UK productivity remains largely unchanged in a decade, we take a look at how the horticulture sector can buck the trend

The Office for National Statistics reported last year that UK productivity had fallen again in the second quarter.

Since 2008 the UK’s level of productivity has remained very static, falling behind other major economies.

The latest AHDB Horizon report, Driving productivity growth together calls for industry to seize the opportunity of the government’s new industrial strategy and forge new partnerships to drive a dramatic acceleration in productivity growth across agriculture and horticulture.

In this context, productivity refers to the amount of work produced per hour or worker; it is not about how much we produce but how efficiently we produce it.

Two indicators are frequently used to measure productivity growth as a whole – total factor productivity (TFP) and average labour productivity (ALP).

TFP measures how effective our agriculture and horticulture sectors are at converting all inputs into outputs. It is a useful and important way of measuring our industry’s productivity over time and against key competitors.

Across the whole of the developed world, rates of productivity growth have slowed over the previous two decades.

Nonetheless, the rate of growth in TFP in the UK has fallen behind that of many of our major competitors, averaging 0.9% per year as opposed to 3.5% in the Netherlands, and 3.2% in the USA. WHY GROWING PRODUCTIVITY MATTERS?

Growing our productivity will improve our industry’s competitiveness to compete with other countries operating in the same markets as us.

In increasingly global markets, the lower our competitiveness, the less able we are to supply British consumers with high-quality, sustainable British food. Low productivity also affects our industry’s ability to seize new market opportunities overseas.

30 AHDB Grower LABOUR & LOGISTICS

LABOUR & LOGISTICS

If our rate of growth had kept pace with the US since 2000, the contribution of UK farming to the rural economy would have been £4.3 billion higher by 2013 A more productive growing sector will benefit our natural environment; techniques that are associated with productivity growth such as precision farming improve the efficiency with which we use natural resources while maximising output.

WHAT CAN WE DO TO GROW PRODUCTIVITY?

Funding agricultural research and design (R&D) has been recognised by the industry and government through the government’s Agri-Tech strategy. In 2015, overall investment in agricultural R&D by both public and private sectors in the UK was around £490 million, putting the UK ahead of some of our main competitors in terms of investment as a proportion of agricultural Gross Value Added (GVA).

There are widespread concerns that the organisation of funding for R&D suffers from poor coordination and strategic direction. This diminishes the scale of R&D and its ultimate impact on the performance of our industry. There is currently no ‘one-stop shop’ of industry knowledge which results in the lack of overall coordination.

Secondly, evidence shows that British farmers and growers under-invest in new skills and training relative to their competitors.

To some degree, the under-investment in skills and training reflects low levels of demand by producers that could be unlocked by generational change and reduce the wide variation in farm business performance and profitability in the UK. VIEW FROM HORTICULTURE

Carol Ford, Commercial Director at AC Goatham & Son, explained how her company is tackling the task facing the UK, saying, “At AC Goatham & Son we have invested in all areas of our business as part of a 20-year strategy for growing the business, but in particular our investment in our orchards and growing technology is significantly increasing our yields and the quality of the fruit.

“Over the last three years the business has embarked on the largest programme of conference pear planting believed to have taken place in the UK for over 40 years. In its first cropping year, 2016, this new planting system produced yields predicted to be around 25 tonnes per hectare, rising to 65 tonnes per hectare at maturity. The current UK average on the old planting system is 17 tonnes per hectare.

“All of our new apple orchards are grown using this new planting system and we are also seeing yield and quality increasing across all varieties.”

SO WHAT DO WE DO NEXT?

The AHDB sets out a five-point action plan, which has at its core increased industry collaboration and partnership to drive lasting change: ●● A nationally coordinated strategy for research and innovation that favours near-market programmes that will unleash productivity gains in the immediate term ●● A new, ‘What Works’ centre for agriculture and horticulture that will act as a beacon for evidence-based change on farm ●● A mandate for AHDB to coordinate Knowledge Exchange programmes ensuring consistent, joined-up and sustained delivery of best practice across all sectors

●● A new, national skills framework for farmers and growers, with careerlong professional development ●● A boost for farmer-to-farmer learning and stretch targets for the uptake of benchmarking and farm management skills

●● We want to hear your thoughts and ideas on driving productivity growth in your business, sector or industry.

Email hort.info@ahdb.org.uk with your views and opinion.

Tom Hind, AHDB Chief Strategy Officer “If key stakeholders are willing to join forces across industry, academia and training providers, in the context of the government’s new industrial strategy, together we can drive a real change in productivity growth.

Productivity growth is of critical importance for two fundamental reasons: Firstly, productivity plays a significant part in our industry’s overall competitiveness, which is critical if we want to operate in increasingly globalised markets. This matters both because we want our industry to seize market opportunities at home and abroad and we want the industry to become less dependent on direct support as we move away from the Common Agricultural Policy.

Secondly, productivity is also a key driver in overcoming the environmental challenges we face. Productivity and environmental responsibility go handin-hand.

The UK has some of the most productive, dynamic and inspirational farming and growing businesses in the world. Yet, as a whole, our industry’s rate of productivity has grown more slowly than in some of our major competitors.

We want this report to be the start of an urgent national debate on productivity growth. AHDB will play its part, and we will be drawing in ideas and inputs from across the supply chain and multiple partners to forge the quickest and best solutions.”

January 2018

You can view all the latest AHDB Brexit Horizon reports at www.ahdb. org.uk/brexit Tweet us at @The_AHDB

Driving productivity growth together

Apr/May 2018 31

AI BRAIN OVER MANUAL BRAWN Could a fully automated broccoli harvester that saves growers significant amounts of time and money soon be a commercial reality? Sarah McWilliam, KMS Projects, updates on the AHDB-funded project aiming to do just that Around 75,000 tonnes of broccoli are grown and harvested by hand each year in the UK. Research commissioned by the NFU showed that increases in the National Living Wage may make this unsustainable for many growers, driving crop production to low cost countries1.

The development of a fully automated harvesting system is therefore crucial for UK growers.

Designing a selective, automated harvester to replace the manual system is no easy task. It must accurately identify and measure the size of each broccoli head and select only those which fit the grower’s pre-determined profile for picking. Then, each selected head must be cut and collected without damaging the uncut crop. All of this must be achieved in real time while the rig is in continuous motion.

COMMERCIAL REALITIES

KMS Projects’ harvester is designed to be a stand-alone rig powered by and mounted on the front of a standard tractor. It uses sophisticated imaging and data analysis techniques to identify the broccoli plants and to select heads of the required size for harvesting. The cutting mechanism is moved swiftly into position by a six-axis robotic arm and the heads cut and lifted leaving the rest of the crop undamaged in the field.

The team built a prototype rig and tested it throughout the 2016 and 2017 growing seasons, refining and improving on various elements of its design before demonstrating it working at twice the speed of a manual cutter to an audience of invited guests in November 2017.

The demonstration was the culmination of a great deal of work, some of it genuinely ground-breaking, to overcome the challenges inherent in this project.

Chief among these was to find a reliable method of accurately accounting for the forward motion of the rig over the field. This is vital so that the location data of the broccoli heads obtained by the imaging system could be used to send the robot to each head with pinpoint accuracy without being affected by changes in tractor speed or the unevenness of the ground.

The demonstration was the culmination of a great deal of work, some of it genuinely ground-breaking

After proving their concept in 2015, KMS Projects have been busy working on a follow-up project (CP 153a) to develop the concept into a single module rig capable of selectively harvesting commercially grown broccoli.

1

32 AHDB Grower INNOVATE

https://www.nfuonline.com/assets/59514

INNOVATE

The harvester collects location and size data about every broccoli head it passes over, including those not immediately selected for cutting Another huge challenge was to find a way for the harvester to reliably identify broccoli curds partially hidden by leaf cover. The solution is perhaps the most exciting aspect of the project. The team have created a method of detection which uses ‘deep learning’ artificial intelligence techniques to train the rig to classify different sizes of broccoli head with impressive accuracy. One of the key advantages of this method is that the imaging system is continually learning from the data it collects.

The HMI (human machine interface) has been designed and work has already begun to integrate it with ISOBUS, taking the concept closer to a turn-key solution.

The rig is equipped with its own communications hub and a user-friendly website interface has been created which will provide access to performance analytics using real-time updates direct from the harvester both to the tractor driver and remotely-sited farm managers.

The harvester collects location and size data about every broccoli head it passes over, including those not immediately selected for cutting. This real-time information can be used for yield mapping and also for improved harvest planning, as decisions will be informed by accurate, detailed data.

THE END GAME

The team’s ultimate goal is to see their prototype developed into a three-module, commercially available machine. This machine will be capable of operating 24 hours a day, without tiring. It will cut broccoli heads that exactly match customers’ specifications, reducing growers’ reliance on manual labour and cutting harvesting costs significantly.

The harvester’s systems and processes which identify, locate and cut broccoli heads have obvious applications with other crops such as cabbage and lettuce varieties.

KMS Projects have a programme of R&D work planned which should deliver the first multi-module prototype machine during 2018. Assuming that operational tests of the prototype are successful, a commercially available multi-module machine should therefore be available to growers in the foreseeable future.

AHDB project code: CP 153a Project leader: Sarah McWilliam, KMS Projects AHDB contact: Jim Dimmock

Apr/May 2018 33

INSIDER INSIGHT PAST LESSONS IN CURRANT-LETTUCE APHID We catch up with Team Leader for insecticide discovery at Syngenta, Gemma Hough, to discover how an AHDB-funded studentship helped her achieve her career goals

Q: Can you give us a quick overview of the project you undertook for your studentship?

A: The project considered key aspects of the biology of Nasonovia ribisnigri which influence its control.

In particular, it made comparisons between biotypes which succumb to (wild-type) or overcome (resistancebreaking), the host plant resistance (Nrgene) in commercial lettuce cultivars.

Experiments were carried out looking at: • Effects of temperature and photoperiod on development • Overwintering biology of eggs • Overwintering biology of nymphs/ adults on alternative host plants • Population dynamics focusing on factors that contribute to the aphid mid-summer crash Results from this project can be used to inform further development of an Integrated Pest Management (IPM) strategy.

Q: Why did you decide this was the route for you?

A: During my Biological Sciences degree I had developed an interest in entomology with a passion for aphids.

When I saw the studentship advertised it seemed like the most suitable progression for me.

Q: What did you enjoy most about your studentship?

A: There were many enjoyable parts to my studentship but I always enjoyed presenting my work to growers and the scientific community. I enjoyed the exchange of ideas and it was rewarding for me to understand how my research could help growers.

The most exciting moment during my project work was when I finally determined the right environmental conditions for stimulating the 34 AHDB Grower VIEWPOINT

production of aphids in their sexual forms which went on to produce eggs.

I had been trying for one year and there was overwhelming joy when I opened the incubator to see eggs covering my currant cuttings.

Q: Conversely, were there any low moments and what lessons did you take from them?

A: Experiments do not always go to plan; whether that be torrential rain during your field trial assessment, or a resource intensive experiment which doesn’t provide the answers you need.

In my opinion these experiences are an important part of developing your skills as a researcher. You learn from your mistakes, plan more robust experiments next time and develop problem solving skills.

Q: How has the studentship helped you in achieving your career aims?

A: I’ve had a very successful career in crop protection so far and I think I owe a lot of that to my studentship as it gave me exposure to the industry and helped me build my network of contacts. My first job after my studentship was at ADAS as a Research Entomologist where I continued to use and expand all the experimental skills and knowledge I had gained during my studentship.

Q: Looking back is there anything you’d do differently?

A: My project was very broad with lots of questions to address. If I was to do this project again I think I would focus on answering fewer questions in more detail - once you answer one question, you create several more to answer.

Q: Would you recommend a studentship to others?

A: Yes, a studentship with AHDB gave me the opportunity to engage with the industry and understand the impact of my research.

Name: Gemma Hough Studentship location: University of Warwick Project title: Biology and control of currant-lettuce aphid, Nasonovia ribisnigri

I’ve had a very successful career in crop protection so far and I think I owe a lot of that to my studentship

HORT THOUGHT

VIEWPOINT

Each issue we ask you to weigh in on a topic that the industry is talking about. This time we take a look at whether you agree with the latest UK environmental strategy

Q: “Do you agree with the government’s new 25-year environmental strategy?”

YES

YES DAVID DAWE, LEAD AUDITOR, NATURES WAY FOODS

ANDY JOHNSON, MANAGING DIRECTOR, WYEVALE NURSERIES

“I’m pleased that at least the government is thinking about our countryside and the environment. But in truth I think it’s just lip-service and hot air as twenty five years in politics is lightyears and this government will be long gone by then.”

“It would be difficult not to agree with the aims set out in the strategy. As an ISO 14001 company we are passionate about plants and their contribution to a better environment and to operating with minimal environmental impact.

It is encouraging to see the emphasis on expanding productive and amenity woodland, improved natural spaces in the urban environment and the conservation of our green heritage.

The horticultural sector has a huge amount to offer in delivering these goals, but it is vital that this strategy is backed up by supportive strategies for the UK nursery industry creating a stable market for UK tree growing and investment in UK nursery expansion.

UNDECIDED CHARLES KIDSON, MANAGING DIRECTOR LOWER REULE FARM LTD “I have yet to read the report in full, but while environmental schemes have benefits they must not exist to the detriment of the nation’s ability to feed itself in a sustainable manner. The percentage of total money invested in schemes on bureaucracy rather than tangible benefits needs to be reduced.”

HERE’S WHAT THE REST OF YOU THOUGHT:

No or Undecided: 33%

The promotion of careers, ensuring access to a source of labour and research and development are but a few of the factors needed. Of course, tougher legislation will be required but the prime driver must be appropriate incentives and support allowing the confidence to adapt to the many challenges quickly. There will be a pressing need for UK grown plants, and as it takes years to deliver trees and shrubs from propagation to planting, with many years of production in the ground at any time confidence and stability are key.”

WHAT DO YOU THINK? Yes: 66%

Have your say and get involved by tweeting us @AHDB_Hort with your thoughts, using the hashtag #Hortthought Apr/May 2018 35

Dishing the dirt New soils resources are available at:

horticulture.ahdb.org.uk/greatsoils • Carrot case study – Martin Evans, Freshgro • Maintaining optimum soil pH • Compost increasing soil organic matter • Engineering the landscape to secure asparagus production

For general soil management resources and content visit:

ahdb.org.uk/greatsoils ahdb.org.uk

@The_AHDB