Agronomists’ Conference 2022: The latest advances in agronomy

The 16th Agronomists’ Conference took place on 6th December 2022, with speakers livestreaming from a venue close to AHDB’s headquarters in Warwickshire. Rachel Hicks reports.

Steve Foster, research entomologist from Rothamsted, was one of the rst speakers at the conference, and he kicked o with the Jurassic Park quote that “life will nd a way” – commenting that this is true of insects and insecticide resistance.

So what is the answer to increased pest resistance? According to Mr Foster, a calculated approach to IPM is needed – new cultivars/ variants that are inherently resistant to pest pressure are undoubtedly helpful, but a well-rounded approach is key, including cultural and safe chemical control options.

Following Mr Foster, Mark Ramsden, of ADAS explained that the more information you have on pest and disease risk, the more informed your decisions can be when it comes to managing that risk.

Mr Ramsden has been working on Horizon 2020 projects around Europe, and stressed the bene ts of using decision management tools in order to support growers’ agronomic decision-making processes. He did, however, say that these tools should not replace personal knowledge, training and experience or the site-speci c needs of a crop in any season – instead they should be used alongside this for optimal crop management.

According to Mr Ramsden, infection risk and management tools help to inform decisions rather than make them, such as AHDB’s BYDV management tool, light leaf spot forecast, phoma leaf spot forecast, sclerotinia infection risk tool and so on.

Most are forecast systems that use weather data in predicting when pests are likely to become a problem for the crop.

There are a number of these in use across Europe, designed to help growers with pest management. One such system is VPS, which has been providing decision support for over 30 years, and AHDB is extending this across Europe with the EU-funded IPM Decisions project, which is designed to be one well-rounded platform which covers every pest risk.

It’s being developed using the input of agricultural consultants, crop protection scientists, weather scientists, software developers, DSS developers, advisors and researchers. Currently, around 50% of the available systems on the platform are relevant to UK growers, and this list will grow in the near future.

For more information visit https:// platform.ipmdecisions.net/login

Diseases: What’s next for variety choice?

AHDB’s Paul Gosling (right) highlighted some of the trial ndings that don’t actually make it into the RL – including the yellow rust variety watch list, lemon wheat blossom midge and clubroot.

The yellow rust population has become very diverse and dynamic, particularly over the last decade, making genetic resistance vulnerable and resistance ratings potentially unstable.

The RL ratings only tell you what happened last year – they are not a predictive tool so won’t always match up with what happens in the coming season.

Launched in winter 2021 and based on RL trial data, the wheat yellow rust variety watch list aims to highlight varieties that may be vulnerable to falls in resistance in the coming year. It has a scale from ‘most resistant’ (against the rust races present in all trials across all sites) to ‘least resistant’ (highly susceptible to one or more races present in at least one trial on one site).

• Most of the varieties classi ed as most resistant had stable ratings

• The largest falls in ratings were seen in those classi ed as least resistant

• Not all of those classi ed as least resistant see falls (highly to one or more races present in at least one

Results last year suggested it worked in identifying varieties at risk – but Mr Gosling asked, how does it look after two years?

The majority of the varieties classi ed as ‘most resistant’ had stable RL ratings, while the largest falls in ratings were seen in those classi ed as least resistant. However, not all those classi ed as ‘least resistant’ saw falls. (See Figure 1)

So, is the wheat yellow rust variety watch list worth paying attention to? Mr Gosling says yes.

The last two years of data suggest the list is highlighting varieties at risk of falls in ratings.

The advice by AHDB is therefore to monitor the varieties identi ed as least resistant on the list more frequently, and be prepared to increase use of rust-active fungicides.

Lemon wheat blossom midge (LWBM)

Anecdotal reports on-farm suggest LWBM (Contarinia tritici) is being seen more frequently in crops. However, it appears earlier than OWBM, so may not be seen in normal crop walking as it may already have been and gone.

LWBM larvae feed on the owers, preventing pollination and thus reducing yield. However, there is little information available on how damaging it is to yield in the public domain.

AHDB has seen LWBM in RL trials. In 2022, a second wheat trial in North Yorkshire was badly a ected.

One of the breeders scored the crop for damage on a scale of 1–9 and took the trial to yield to see how yield loss would be impacted. The yield loss in crops rated 9 compared with those rated 1 was around 2.14t/ ha. None of the control varieties were signi cantly a ected by LWBM, so

Wheat and barley – registered products

ProductActive(s)

Mode of Action

Arizona*folpet Multi-site

Proline 275prothioconazole DMI**

Myresamefentri uconazole (Revysol) DMI**

Imtrex uxapyroxad SDHI

Elatus Plusbenzovindi upyr (Solatenol) SDHI

Peqtigafenpicoxamid (Inatreq) QII

Ascra Xprobixafen + uopyram + prothioconazoleSDHI + SDHI + DMI**

Elatus Erabenzovindi upyr + prothioconazoleSDHI + DMI**

Revystar XEmefentri uconazole + prothioconazoleQII + DMI**

Univoqfenpicoxamid + prothioconazole QII + DMI**

A further seven unregistered products were tested in 2022. Data on these will be released upon registration

*Arizona tested at full dose (100%) only **Azole Check labels prior to use: Imtrex, Myresa, Peqtiga, Elatus Plus shoild be used in mixtures with at least one fungicide with an alternative mode of action that has e cacy against the target disease.

…from previous page provided a good comparison.

Mr Gosling was keen to point out that this was based on a single trial, so any results come with the caveat that more research is needed.

However, the results of this rst trial suggest that LWBM can have signi cant yield impacts.

While the life cycle of LWBM isn’t 100% clear, it probably needs similar conditions to OWBM – warm and wet in May, with soil temperatures above 13ºC. However, eggs are laid earlier than OWBM, at around GS 51–55.

There is no varietal resistance known, but some breeders are currently working to nd it. No crop protection products currently have LWBM on the label.

One good thing is that LWBM seems to be less persistent in the soil than OWBM – up to three years but maybe as little as two, so rotation should be e ective at helping to control it.

Clubroot appearing in some trials

AHDB has seen clubroot in a couple of trial sites which had no previous history of clubroot over the last two years. In both cases, the clubroot became evident in the autumn and, rather than abandoning the trials, the team took them through to yield to see what impact the infection had.

At the Berwick RL trial in 2021, the site had a medium soil texture, with winter OSR grown four years previously.

The eld was limed prior to drilling, which happened on 20th August.

By 20th October, clubroot symptoms were discovered fairly uniformly throughout the trial. Galls and clubbing on the roots were obvious, with some plants becoming stunted and failing to ower. The symptoms were scored and the trial taken to yield.

Crome, being the only clubrootresistant variety being trialled at the site, was the only variety in the trial to not be signi cantly, a ected, yielding approximately 1.5t/ha above the average.

So is the clubroot risk increasing?

Autumns seem to be increasingly warmer and wetter – and infection is most likely to occur in warm, wet soils, which helps zoospores to disperse (optimum temperature being 16–25ºC).

Crops are most susceptible to infection from August–midSeptember, and most vulnerable at one to two leaves unfolded.

Delayed drilling minimised the potential window of infection and helps the crop to avoid clubroot. Crops drilled earlier to avoid CSFB will be more vulnerable to clubroot. Mr Gosling does pose the question of whether the widespread use of cover crops could be making the clubroot problem worse.

With some cover crop mixes having brassicas in, Mr Gosling says he hopes growers who include OSR in their rotation are making sure to keep away from such mixes, but he also points out that other mixes could potentially be hiding brassicaceous weeds.

Fungicide performance update for wheat, barley and OSR

Rebecca Joynt (right) of ADAS explained that the fungicide performance project aims to evaluate different fungicides and their relative performance against different diseases to provide independent data to support decisions when creating a spray programme.

When it comes to choosing fungicides, the key points are:

• Match fungicides to the primary disease risk, which depends mainly on variety, sowing date, location and local weather/ microclimate

• Mixtures and alternations of fungicides with different modes of action, from different fungicide groups, are often the most effective and reduce the likelihood that fungicide resistance will develop in pathogens

• Resistance poses a significant threat to the performance of fungicides. Therefore it is essential to take resistance management into account when planning fungicide programmes.

The trials are designed to create high pressure scenarios, including high risk locations, highly susceptible varieties, and evaluation using a single spray timing. Both protectant and eradicant activity are evaluated separately.

In the 2022 wheat fungicide trials, 10 di erent fungicides were tested, six of which contained a single mode of action (straights) and four were mixtures containing di erent modes of action (see Table 1).

A further seven products, which aren’t currently commercially available, were also tested and data will be made available upon registration.

Wheat results

As a summary of the results, the 2022 sensitivity monitoring data shows no significant shifts, and all isolates tested were within previous ranges. Mefentrifluconazole and fenpicoxamid are the leading actives, with mixtures containing these (i.e. Revystar and Univoq) giving the highest levels of control.

Septoria populations are heterogenous and individual samples vary considerably by site and season. However, ADHI and azole isolates with reduced sensitivity are slowly accounting for an increasing proportion of the population. These less sensitive isolates are becoming more complex, carrying an increasing number of mutations.

Pre- and post-application monitoring shows a single fungicide application is sufficient to drive changes in the septoria population, so it remains critical that resistance management measures are built into spray programmes: mixtures, alternation and multi-sites are key components of this approach.

In the yellow rust trials, Elatus Era was particularly effective but all mixes performed well. Meanwhile, mefentri uconazole and SDHIs tested were highly active on brown rust, with fenpicoxamid and prothioconazole showing useful activity.