Undercover
farming
ucf
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NOVember/DECEMber 2020 Volume 17 No 6
I I R45.00 per issue
HYGIENE
DISEASES
SCOUTING
CUCUMBER
Hygiene in the fresh produce packhouse Page 4
Pythium disease on greenhouse crops Page 11
Scouting for pests and diseases Page 14
Improving cucumber yield Page 18
Wishing you well over the Festive Season & Every success for 2021!
Undercover growing solutions to help your business flourish
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info@vegtech.co.za
greenhouses I shade net I hydroponics I aquaponics PROPRIETOR I ADVERTISING SUZANNE OOSTHUIZEN 082 832 1604 suzanne@axxess.co.za EDITORIAL CONTENT & COMPILATION Johan Swiegers 082 882 7023 editors@axxess.co.za ADDRESS PO Box 759, Montana Park 0159 E-MAIL magazine@axxess.co.za FAX 086 518 3430 DESIGN Fréda Prinsloo PRINTING Business Print Centre DISCLAIMER Undercover Farming accepts no responsibility for claims made in advertisements or for opinions and recommendations expressed by individuals or any other body or organisation in articles published in Undercover Farming. COPYRIGHT Copyright is reserved and the content may only be reproduced with the consent of the Editor.
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Contents 4
How to correctly manage total alkalinity for different crops
5
Advantages of planting seedlings versus direct sowing
7 Hygiene in the fresh produce packhouse 8 Training on hydroponics systems & capacity building 10 Obtaining optimum fruit set 11 Pythium diseases of greenhouse crops 14 IPM & greenhouse insect pests – scouting and
FRONT PAGE: Even growing seedlings in Hishtil’s seedling greenhouses. Read p5.
INSIDE ...
record keeping
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Technological advanced grow systems for leafy greens
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Improving cucumber yield with optimal drip fertigation
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Subscription form
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any of us would rather not communicate over the events of the past year. But then, how sad it was for some to have lost loved ones, jobs, glimpses of future careers, still, there are so many testimonies reaching us daily of how people started to think ‘out of the box’, as it were. Some changed career paths; some farmers changed their practices or adapted to keep doing where they live to survive and even their wives started small enterprises. Flowing from these we are sure to publish success stories in the near future. We are over-joyed at good rains that fell across the country and even in severe drought stricken areas where no rain fell for around eight years. Imagine having been born and experiencing your first rain event at eight! We are again confronted with certain lock-down regulations by government but through it all, we still maintain; people must eat to live. Looking over the subjects in this final edition of 2020, we cover a variety of aspects pertaining to undercover farming. Training of management, staff and greenhouse assistants is an on-going process (maybe that is why it is called ‘train’-ing?). Hygiene, discussed in our GAP editorial is possibly top of the list in greenhouse keeping currently and should be followed to the tee in order to keep the quality of South African produce high and internationally recognized. For many, this is high season, some are bogged down, especially around the coastal areas, but people during the Festive Season tend to consume more than on average through the year, therefore we believe our undercover farming producers will be able to supply timeously to their markets. Let us not lose hope for the future – what your hand is at, do not look back at 2020 and the pandemic, let us stick to what we do best, and do it wholeheartedly. Blessings to all and your families!
A Christmas Blessing “And he rose and took the child and His mother by night and departed to Egypt and remained there until the death of Herod. This was to fulfill what the Lord had spoken by the prophet, “Out of Egypt I called my Son.” (Matthew 2:14-15) This is another angle to focus our thoughts around the event of Christmas. Reading the scripture, one realizes that, although the birth of Jesus was planned by God, events turned against the ‘natural’ development of the plan. However, further reading reveals the immediate reason and eventual return to Israel in order to fulfill the promise by God to offer His Son as Saviour for sinful mankind. Be mindful of our situation globally today – are we not facing a similar situation in some way? Let us devote ourselves during Christmas to the Son, being the greatest Gift to mankind!
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How to correctly manage alkalinity for different crops
total
Concrete irrigation canals are used to feed slightly acidic water from the Clanwilliam dam to the Vredendal irrigation area. Contact between the water and the alkaline cement adds alkalinity to the water.
When feeding water is chemically analysed, the total alkalinity should also be measured. Acidloving crops such as blueberries are grown at pH levels between 4.5 and 5.0 (total alkalinity; 0.0 - 0.2 meq l-1).
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ormal greenhouse crops are grown at pH levels between 5.3 and 6.3 with the optimum pH at about 5.8. In order to reach the desired pH level in a nutrient solution, the total alkalinity of the
feeding water need to be at the correct level. Normal greenhouse crops are grown at alkalinity levels between 0.2 and 1.0 meq L-1, depending on the crop and the production system. Experience will help growers to choose the correct total alkalinity for their feeding water and production methods in order to reach optimum pH-levels; however, the following background may help:
Since most crops need high levels of nitrate, nitric acid is generally used to treat the feeding water for normal greenhouse crops. However, some growers prefer to apply phosphate with phosphoric acid.
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Pre-setting of alkalinity Crop: A relatively low total alkalinity is needed for acidloving crops such as disas, azalias and blueberries (0.0 – 0.2 meq L-1). Levels
Experience will help growers to choose the correct total alkalinity for their feeding water and production methods in order to reach optimum pH-levels. between 0.2 up to 1.0 meq L-1 can be chosen for normal greenhouse crops, depending on growth conditions. Substrate: Since organic substrates release bicarbonate during decomposition, an increased root zone alkalinity (pH) can be expected as the substrate decomposes over time. Thus, a relatively low total alkalinity can be chosen for nutrient solutions on organic substrates (acid-loving crops ±0.0; normal crops ±0.4 meq L-1). Where inert substrates are used (sand, gravel or rockwool), a higher total alkalinity may be chosen (acid-loving crops ±0.2 meq L-1 and normal crops ± 0.8 meq L-1).
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Farmers are facing a constant battle of increasing input cost. This is not limited to fertilizer and chemicals, but seed cost has increased exponentially in the last year.
Advantages of planting seedlings versus direct sowing
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ith the increased cost the risk of direct sowing cucurbits is become more difficult to justify and manage. Sending expensive seed to Hishtil SA can reduce the risk by ensuring the best performance is gained from seed and the highest quality seedlings are planted in the field. The following advantages are seen with farmers that made the switch from seed
to quality seedlings: • Uniformity – due to planting of uniform seedlings. • Improved final field stand and more efficient harvesting. • Losses of expensive seed can be minimised by effective use of plugs • Risk reduction due to shorter exposure in the field to pests and diseases such as rodents. • Using of seedlings will usually lead to earliness in yield. • Overcoming germination losses in harsh climatic conditions such as extreme heat and cold. • Saving of water and other resources due to reduced time in the field. • Improved planning and crop cycling due to predictable seedling delivery times from the nursery in turn leading to improved planning. • Allows usage of grafted seedlings to overcome soil borne pathogens and enhance vigour . An important point when moving from seed to seedlings is the fact that direct sown plants will develop a deep tap root. This does not happen with seedlings as the root system develops differently. Watering techniques should be adapted accordingly. For more information contact Hishtil SA at 015 395 4034 or e-mail to sales@hishtilsa.com
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+ levels. Disas also grow well at high NH4+ levels and should be considered as an acid-loving crop. Alkalinity buffer Ammonium in the nutrient solution: Should you plan to use a nutrient The EC of pure rainwater is 0.0 mS solution with a high ammonium level cm-1 with a pH of 7. Adding a drop (>1.0 meq L-1) on normal greenhouse of acid to this water may decrease the crops, then the pre-set alkalinity may pH substantially. Should a drop of acid be lifted to counteract the expected be added to the same volume of high acidifying effect of ammonium in the EC-water with a pH of 7.0, the pH will root zone. decrease much less. Fertilizers: Some water-soluble To understand this, it must be fertilizers such as mono potassium remembered that the H+: OH- ratio phosphate (MKP) and certain potassium is 1:1 at pH 7. For argument’s sake, sulphate products may have acidifying say that the ratio H+: OH- in distilled effects. When these fertilizers are added water is 10:10 and 1000:1000 in high to water with a low total alkalinity, EC water at pH7. Then, by adding a the pH will drop. To counteract the drop of acid with 90 H+ ions to rain expected drop in pH, the total alkalinity water, the H+: OH- ratio will change of the feeding water can be set a bit from 10:10 to 100:10 and the pH will higher. drop to 6.0 (10 times more acidic). Adding the same drop of acid (90 Alkalinity too high or too low H+) to high EC water (well buffered), Most soils are well-buffered, which the H+: OH- ratio will change from means that their pH values do not 1000:1000 to 1090:1000, causing only change easily. This is not the case for a small increase in acidity and only a soil-less conditions. Special precautions slightly lower pH. are needed to control the pH and Distilled water and rainwater are consequently the chemical and physical examples of water with a neutral pH form and availability of nutrients in the and a zero total alkalinity. The total solution. Some nutrients precipitate as alkalinity of water insoluble salts in from mountainous high pH solutions, Distilled water and rainwater high rainfall areas and these particles are examples of water with may be zero or may block drippers. a neutral pH and a zero total slightly acidic Compared to pH values of soil, alkalinity. The total alkalinity (corrosive) due to organic acids. Since the optimum pH of water from mountainous metal and asbestos of hydroponic high rainfall areas may cement water solutions may seem be zero or slightly acidic pipes deteriorate to be relatively low. (corrosive) due to organic when exposed to Having a look at the corrosive water, acids. dissociation pattern municipalities are of phosphate in forced to increase the alkalinity of their solution (Table 7), the optimum pH for acidic water sources. phosphate absorption should be slightly Due to the extremely low solubility of acidic. Since some micronutrients such lime, as shown in Table 15 (CaCO3 = as Fe and Zn precipitate at high pH 0.014 g L-1), it can be used to remove levels, forming insoluble salts, their acidity and add some alkalinity to absorption is also restricted at high pH corrosive water without the danger levels. of an over dosage. This implies that At pH values lower than 5, problems distilled water can be soaked in lime and may arise on crops that are sensitive to CA deficiencies (peppers and tomatoes). that a maximum of only 0.014 g L-1 will dissolve (14 mg L-1 /50 =0.28 meq L-1) This is due to high H+ concentrations lifting the alkalinity from zero to 0.28 that may suppress the absorption meq L-1. of Ca2+ and other cations. A high ammonium (NH4 +) level will aggravate Concrete irrigation canals are used to feed slightly acidic water from the Clanthis problem since it may also suppress William dam to the Vredendal irrigation the uptake of other cations. Therefore, area. Contact between the water and most soil-less crops are grown in the alkaline cement adds alkalinity to solutions with pH values ranging from the water, as it flows to growers further 5.3 to 6.3. The acid-loving blueberry down-stream. This increase in alkalinity is grown at pH 4.5 to 5.0 and is also is more noticeable during winter adapted to grow at relatively high NH4
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months when the need for irrigation water is small, resulting in a slower water flow, allowing a longer period of contact between the water and the concrete canal. The same effect may be noticed where water is conducted in asbestos-cement pipes. Decrease alkalinity The release of carbon dioxide (CO2): With the addition of acid to bicarbonate (representing total alkalinity), the end products are water and carbon dioxide (CO2), as seen in the following equation: H+ + HCO3 - ↔ H2O + CO2↑ This reaction is suppressed when the release of CO2 is prevented, and the pH will then not be lowered sufficiently. This happens where >0.8 meq L-1 of an acid is applied to the water under pressure. Using an acid application machine (injecting acid into a pipe with flowing water or nutrient solution under pressure) the maximum application should not exceed 0.8 meq L-1. Feeding water with a high total alkalinity, with an acid need of more than 0.8 meq L-1, should thus be treated in an open container, allowing the gas to escape before fertilizers can be injected.
Choosing an acid By using nitric acid (HNO3), or phosphoric acid (H3PO4) or sulphuric acid (H2SO4) as H+ sources, the bicarbonate (HCO3 -) in the feeding water can be replaced with NO3 -, H2PO4 - or SO4 = respectively. Since most crops need high levels of nitrate, nitric acid is generally used to treat the feeding water for normal greenhouse crops. However, some growers prefer to apply phosphate with phosphoric acid. Blueberry growers may avoid high nitrate levels (associated with nitric acid) by choosing sulphuric acid. Due to the formation of insoluble phosphates and sulphates at high pH levels (blocking drippers), phosphoric acid and sulphuric acid should not be applied to water with a total alkalinity of >1.9 meq L-1. Nitric acid should then be used to lower the total alkalinity to <1.9 meq L-1 before phosphoric or sulphuric acids may be applied. Author: Dr NJJ (Nic) Combrink of the Horticultural Faculty, University of Stellenbosch. Readers who wish to obtain his new very valuable updated manual on Nutrient Solution Management, may contact Dr Combrinck at njjc@sun.co.za
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Hygiene in the fresh produce packhouse Postharvest practices in fresh produce farming involve transporting, sorting, washing, and storing or packing the crop. Although this information may seem to some producers as being over emphasised, it still remains extremely important to use Good Agricultural Practices because fruit and vegetables are on every consumer’s plate.
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ost critical to the handling of fresh produce after harvesting are; “Clean hands,” “clean water,” and “clean surfaces.” As with harvesting, the farmer has to ensure that workers are healthy and trained to use proper hygiene. In the pack house, all surfaces, for example; boxes, grading tables, knives, vehicles, and, of course, hands that come into contact with fresh produce have to be sanitized. Use only clean (potable) water for washing and cooling, making sure that there aren’t any pests like rodents or birds in the pack house. Producers must realize Good Agricultural Practices do not exist by themselves; it is part of a larger picture of efforts to ensure that our food is safe to eat, and to verify that farms are implementing GAPs appropriately. There are three major issues in the area of farm food safety: buyer requirements, regulatory requirements, and moral/ethical standards (doing the right thing for people consuming the food you grow). With the global focus on Good Agricultural Practices to verify that farms are producing fruits and vegetables in the safest way possible, the retail and food service industries are using third-party GAP audits to verify that their suppliers are complying with specific agricultural practices. GAP audits based on globally accepted farm food safety principles and practices are executed in all countries.
Wholesale and retail buyers of fresh produce want to limit their businesses’ risk of being part of a foodborne illness outbreak. They want to protect their name or brand, and they don’t want to lose money because of an outbreak. Therefore, it has become very common for wholesale buyers to require the farms they buy from to follow GAPs. Pickers and packers Harvesting and pack house assistants’ health and hygiene is the most important part of a food safety program, but it is often the most difficult to implement, which is why it is so important to train workers in farm food safety practices. Food safety practices are implemented, but regular training is the key to its success. Workers are a critical part of any farm food safety plan because they are responsible for using food safety practices every day while they work. Workers can carry human pathogens (microscopic organisms that can cause illness) such as shigella, bacteria that cause dysentery (persistent diarrhea
A picker should wear clean head gear, clean clothing or overalls, clean shoes and harvesting equipment to work with.
and loss of body fluids). In some cases, acute kidney failure and death occur. It is contracted orally by direct contact of faeces with foodstuffs (hands that became contaminated after using the bathroom without being properly washed). Salmonella is another type of bacteria found in faeces and soil and survives for up to nine months in water. It is transmitted by eating fruits, vegetables, or water contaminated with faeces from an infected animal or person. Furthermore, Hepatitis A, a very contagious virus causes liver inflammation, diarrhea with stomach pains, jaundice (sudden yellowing of skin and eyes), dark urine, fever with headache, and nausea. Norovirus is often associated with cruise ships where crowded conditions
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Training on
hydroponics systems & capacity building To implement a Successful Hydroponics system in your Greenhouse Operation, you need thorough training as a Farm Manager. Your team needs hands-on Capacity Building as well to gain operational Skills. General
H
ydroponics Greenhouse Farming is a hot topic today. Many farmers and new entrants to food production require information to start an operation. In this article we focus on Training and Capacity Building needs for you as a Farmer, Farm Manager or Management Team member. Training of staff is usually the next step, executed by the management team itself. They would have received training with the concept of â&#x20AC;&#x153;Train-the -Trainerâ&#x20AC;? and afterwards, are capable to train their staff. Business plan and System Requirements The first step is to create a Business plan with an off-take agreement in place, to showcase that your plans are viable. With a Feasibility Study including a Technical Design you are then ready to head to funding or financial institutes, and afterwards approach greenhouse suppliers for quotations.
Construction Phase As soon as the aforementioned steps are in place with finance or funding approved and the most suitable Greenhouse Supplier contracted, the construction phase starts. Usually during this phase training of greenhouse staff takes place. Logically, as the first (future) Management Team Members are recruited and they observe the project grow until being completed and handed over to the owner. Construction Supervision and the elementary part of training happen simultaneously. Training Content The training syllabus encompasses all crop related topics. Starting with;
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Variety choice, Climate Control, Plant Management, Irrigation & Fertigation, Plant Health requirements, Labour Management tools and Data Recording to provide Management Information. A proper training location is preferable, e.g. a board room near to the greenhouse operation in order to offer participants first hand practical experience of implementing their theoretical knowledge after the formal workshop. Cultivation Workshop students cannot wait to start their first crop which is called the Cultivation Phase. During the first months of the cropping phase participants complete their training, and after a few weeks, or months (depending on the crop type), they are ready to harvest.
Coaching by a Delphy Consultant During the Cultivation Phase it is crucial to
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spend as little as possible on school fees. Of course there is a learning curve (e.g. 2-3 years), before participants reach their full potential. But that curve is anticipated to be as short as possible and with a high success rate (target set at 80% in the first year). The Delphy Consultant plays the role
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Delphy trained students filled with joy over their competency certificates. Herbert Stolker, Senior Consultant of Delphy appears with them in the photo.
of knowledge partner in all the abovementioned processes. From Business plan through Construction phase, training up to Coaching of the Farmer and his Managers is a comprehensive service offered by Delphy. The coaching is usually by contract for the first growing season (1 year) but in practice, the actual clients (greenhouse owners) renew the contract year after year. Hygiene in the fresh produce
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cause the virus to spread rapidly. People become infected by eating food or drinking liquids contaminated with Norovirus, touching contaminated surfaces or objects and then touching their mouths, and causes sudden onset of diarrhea, vomiting, nausea, and abdominal cramps. Workers’ hands can also be a source of contamination if they do not wash them properly with soap and water after going to the bathroom or returning from a break (e.g., after eating/snacking or smoking) and then handling produce. The fecal–oral route is the most common way for produce to become contaminated. Cross-contamination occurs when bacteria or pathogens are carried from one object to another. It can happen in many different ways, including from: dirty clothing, contaminated footwear, contaminated tools or equipment, cuts, open sores or bruises. With the Covid 19 epidemic in mind, pathogens spread by coughing, sneezing, spitting or just touching the mouth, working in too close proximity with others and not wearing masks, should be made aware of imminent dangerous situations.
Training and awareness Training employees about constant awareness when and how to properly wash their hands is of utmost importance. Workers must wash their hands when
Herbert Stolker of Delphy, at a training session on hydroponics basics with attendees.
Many Greenhouse Suppliers include Delphy’s services in their quotations. For them it is important to have another satisfied customer who successfully operates in his/her business.
Added value By this cooperative method, the added value is obvious. A smooth-running farm operation with skilled and encouraged workers and a committed management team are a recipe for success. they are contaminated by any of the abovementioned actions. Worker training should include how to wash hands properly, and provide the chance to practice this skill during the session. For growers, farm workers, packers, and shippers, prevention is the key to controlling potential microbial hazards and sources of contamination. Preventing problems before they become critical contamination hazards is of utmost importance in any fresh fruit or produce operation. Studies have shown that once contamination occurs, it is very difficult to remove all pathogens.
Visitors Visitors include people (other than hired workers) who enter the farm with permission (like “pick-your-own” customers, agricultural tour groups, and school groups). Visitors should be made aware of basic sanitation and hygienic principles on the farm. They must be made aware of food safety policies set by the farm and have access to toilet and hand washing facilities. Policies can be reviewed with visitors through posters, hand outs, short policy summaries, or verbally when they enter the farm. Personal hygiene and awareness Good personal hygiene begins at home. Being clean and in good health when at work, show workers respect the health of others and the produce they work with. Workers should be motivated at each
Many commercial South African farmers as well as small-scale farmers are satisfied customers of Delphy services over a number of years. These ascribe their success to the thorough training Delphy offers. Today’s Greenhouse Cultivation is Topsport! You need Professionals in your team, including a good Coach. By: Herbert Stolker, Senior Consultant at Delphy, based in KZN. meeting to apply these habits at home, and also convey this message to their families. Workers are critically important in preventing contamination in the field, during harvest, and in the packing shed. They are on the “front line” as the ones most closely and most frequently involved in viewing, selecting, harvesting, and handling produce. It is very important that workers be trained and empowered to recognize, respond, and confidently report to their supervisors any conditions in the field and in the packing house that may potentially contaminate produce. Importantly of course, workers should not be a source of contamination to themselves. The Worker Environment Equally important, is the environment in which it is expected the worker or assistants must operate successfully. Not only the farm office, kitchen and bathroom must be hygienic, but the workers environment; their tea break space, bathrooms, showers, locker rooms and working clothing and boots must be kept in hygienic condition at all times. The foreman of the harvesters, truck or tractor drivers, pack house manager, must all at all times be diligent in GAP rules of the business. Regular meetings over farm practices and crop hygiene must be held and kept record of in pursuing GAP and produce excellence. Source: GAP Training.
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A producer prepares for a bumper season, but finds along the way he was not pro-active against poor fruit set which could lead to a serious financial setback. With high input costs currently experienced and having lost through this yearâ&#x20AC;&#x2122;s economic slump, the greenhouse farmer needs to be proactive in his planning towards good fruit set.
Obtaining optimum fruit set The photo shows irregular set where a few fruit on the truss set very early compared to the rest. These fruit will always dominate, and there will be a big discrepancy in both fruit size and time of harvest that will have an impact on the financial returns.
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hen comparing varieties, growers often use yield as the most important determining factor. Surely the tomatoes must also be of high quality and therefore market ready, the disease resistance good and the harvesting team ready. But what makes one variety different from another when it really comes to yield advantage? Yield is made up of two factors â&#x20AC;&#x201C; fruit size and fruit number. Fruit size is affected by the genetic capacity of the variety, the overall fruit load, management and climatic conditions. Most growers assess relative fruit size
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All things being equal, this is usually a reaction of the ability of the variety to set fruit, i.e. to turn flowers into fruit. This is the one single factor that sets two optically during the Very often a grower will varieties apart in growing life of the use fruit size as a critical their ability to yield crop and only pay selection factor and will well, particularly particular attention to under difficult dismiss a variety as having the fruit size at the end conditions. fruit that is too small (on of the crop cycle. Very An assessment of observation only) without often a grower will use a widely planted fruit size as a critical really paying any attention variety, reiterated selection factor and to the overall yield. the importance will dismiss a variety of thorough and as having fruit that is uniform fruit set. The seedlings were too small (on observation only) without transplanted in early January and the really paying any attention to the overall third truss was showing yellow flowers yield. at the time of assessment. What was What probably is more valuable to 11 assess, is fruit number or fruit load.
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flowering means pollination at the same time, leading to even fruit size and also ripening and harvesting at the same time.
immeÂdiately obvious was that trusses one and two had suffered from poor set. On each truss only two or 3 flowers had set fruit. The rest have dropped off, or would set so far behind the primary Ultimately, fruit that it is too small according to the this is an easy market requirements. This meant that observation to at least three flowers per truss have make, while failed to set. intuitively one knows that good During January and February extremely fruit set is better, high temperatures prevailed and despite but what is this the best efforts of the grower the characteristic conditions were too extreme for this really worth to the variety to set fruit properly. A similar grower? trend was also experienced in early summer at the same farm, thus one There are some basic can easily conclude that this particular calculations one needs to do. variety, while good in other ways, has a For instance, should problem with fruit set in only the first two Uniform flowering the heat. trusses be problematic, means pollination at the assuming that the later In comparison, same time, leading to trusses set 100 per experimental varieties under evaluation showed even fruit size and also cent, then one can not only complete set, ripening and harvesting calculate the lost value per fruit, and per ha but also uniform set. at the same time. for different market On each truss five to six prices. For his high fruit have set more or quality fruit the grower would probably less at the same time, and conspicuously expect to average a current average on the flowering truss, all the flowers gross return for his total crop. By losing were open at the same time. Uniform
two flowers on just the first two trusses of each plant, due to poor fruit set could cost a grower a grand percentage of his estimated total yield. To make this situation even more painful, this loss is from the net profit, as all the planting, establishment and production costs still have to be paid, whether there are five fruit on the truss or three. Absolute set, where either a fruit sets or the flower drops, is not the only important factor â&#x20AC;&#x201C; equally important is the ability to set fruit on a truss at more or less the same time. Therefore, when selecting a variety, pay attention to the uniformity of flowering, the uniformity of fruit set and the ability to set fruit under a range of climatic conditions. This one point could make a huge difference to the producersâ&#x20AC;&#x2122; net income! By: M. Burnett
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Pythium species are fungallike organisms (Oomycetes), commonly referred to as water moulds, which naturally exist in soil and water as saprophytes, feeding on organic matter. Some Pythium species can cause serious diseases on greenhouse vegetable crops resulting in significant crop losses.
Pythium diseases of greenhouse crops
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Pythium species are fungal-like
organisms (Oomycetes), commonly referred to as water moulds, which naturally exist in soil and water as saprophytes, feeding on organic matter. Some Pythium species can cause serious diseases on greenhouse vegetable crops resulting in significant crop losses.
roots which can survive prolonged adverse conditions in soil, greenhouse growing media and water, leading to subsequent infections.
Figure 1. The disease cycle of Pythium damping-off and
crown and root rot of greenhouse vegetable crops. Pythium infection leads to damping off in seedlings and crown and root Disease cycle rot of mature plants. Several Pythium Pythium can be introduced into a species are known to cause damping-off greenhouse in plug transplants, soil, and crown and root rot in greenhouse growing media and plant refuse and cucumber, pepper and tomato crops. irrigation water. Greenhouse insects There are no Pythium resistant varieties such as fungus gnats (Bradysia impatiens) available although some varieties may and shore flies (Scatella stagnalis) can have disease tolerance. also carry Pythium, which spreads by Over-watering, poor root aeration, forming sporangia, sack-like structures, root injury and improper root zone each releasing hundreds of swimming temperatures can weaken the crop zoospores (Figure 1). and, thus, trigger Pythium outbreaks. Zoospores that reach the plant root Saturated growing media that are either surface encyst, germinate and colonize too cold or too warm can be conducive the root tissue by producing fine threadto Pythium build up and spread in water like structures of hyphae, collectively and recirculating nutrient solution. Plants called mycelium. These hyphae release grown under optimal environmental hydrolytic enzymes to destroy the root conditions are less susceptible to tissue and absorb nutrients as a food Pythium than plants grown under poor source. Pythium forms oospores and conditions. chlamydo-spores on decaying plant
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Symptoms ‘Pre-emergence’ damping-off causes seeds and young seedlings to rot before they emerge from the growing medium, while ‘post-emergence’ damping off kills newly emerged seedlings. In ‘postemergence’ damping-off, the pathogen causes a water-soaked, soft brown lesion at the stem base, near the soil line, that pinches off the stem causing the seedling to topple over and die. In mature plants, Pythium causes crown and root rot, where plants suddenly wilt when weather turns warm and sunny and when plants have their first heavy fruit load. Often, upper leaves of infected plants wilt in the day and recover overnight but plants eventually die. In the root system, initial symptoms appear as brown to dark-brown lesions on root tips and feeder roots and, as the disease progresses, symptoms of soft, brown stubby roots, lacking feeder roots, become visible (Figure 2). In larger roots, the outer root tissue or cortex peels away leaving the string-like vascular bundles underneath. Pythium rot also occurs in the crown tissue at the stem base. In cucumber, diseased crown turns orange-brown in colour, often with a soft rot at the base; brownish lesions extending 10 cm up the stem base may be seen. Monitoring & Identification Routinely monitor your crop for slightly wilted plants and check wet
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ultrafiltration (membrane filters), micropore filtration (high pressure, rapid flow areas in the greenhouse where Pythium membrane or sediment filters), heat is more likely to be present. Pythium pasteurization (95-97°C for 30 seconds occurs mostly in spring, at early fruit set or 85°C for 3 minutes), UV radiation, and later in the season on mature plants. sonic energy, magnetism, aeration (i.e. In cucumber, Pythium can also occur in oxygenation), ozonation, etc. the summer on young plants brought in Biological – bio-filtration (slow sand or for the fall crop. lava rock), water retention ponds. Monitor plants for wilting, and in Chemical: chlorine, chlorine cucumber, check the stem bases for dioxide, copper, hydrogen peroxide, discoloration. Always confirm Pythium electrochemical, soaps (wetting agents), diseases by sending representative plant iodine, etc. samples with roots, crowns and foliage to a plant diagnostic laboratory. Resistant varieties: Although there are no resistant vegetable varieties, Integrated Disease Management some vigorous varieties may have Disease management consists of a some tolerance to Pythium. Contact combination of cultural, biological and your local seed/transplant supplier for chemical tools to control and/or manage further information on Pythium tolerant crop diseases effectively. Cultural varieties. controls keep Pythium from reaching Seedlings & Transplants: Transplant the roots while biological and chemical in the morning or late afternoon/ controls inhibit or suppress Pythium in evening to avoid stress from high day the root zone. time temperatures. Allow for good Cultural Controls air circulation around seedlings by Sanitation: Field soil, debris, pond and proper plant spacing and good aeration stream water, and roots and plant refuse of irrigation water and re-circulating of previous crops can contain Pythium. nutrient solution. Use healthy Follow a strict greenhouse sanitation transplants and handle them carefully program throughout the year and a to avoid wounding plants and roots thorough year-end clean up. Clean and and practice good sanitation when disinfest all interior greenhouse surfaces transplanting; do not let them dry and equipment including tools, hoses, when setting out. Water seedlings in walkways, carts, totes, troughs, tanks the morning so that plants are not wet and water supply lines. Use sterile overnight. propagating media. Remove dying plants Plant growing conditions: Ensure that by placing them directly into plastic bags transplants have the proper root zone for disposal away from the greenhouse. temperature and adequate moisture Irrigation water: Untreated water from when moved into the greenhouse. The rivers or streams poses great risk for growing media must be well drained as Pythium introduction, while treated saturated bags with low oxygen levels municipal water is considered safe from can predispose transplants to Pythium Pythium. Water storage and nutrient diseases. tanks need to be Use warm, aerated disinfected periodically irrigation water (18Very often a grower will and covered to prevent 22°C). Avoid low use fruit size as a critical Pythium contamination. light levels, low pH, selection factor and will Nutrient Solution: high salts and warm dismiss a variety as having Generally, greenhouse growing conditions vegetables are raised (above 28°C) which fruit that is too small (on on rockwool in favour Pythium. observation only) without plastic sleeves or bags In greenhouse really paying any attention containing rooting cucumbers, the to the overall yield. medium (i.e. rockwool nutrient solution slabs, sawdust or should be delivered coconut fibre) through which water and at pH 5.0 for approximately 5 weeks nutrient solution are circulated. Since followed by adjusting the pH to a Pythium and other pathogens can build 5.8-6.2 program for one week. Target up in nutrient solution, periodically rockwool block wetness at 70-75% disinfest recirculating nutrient solution between watering. using physical, biological or chemical Use white/colourless drip lines instead methods. of black or place drip lines on the shaded side of the grow bags. Filtration methods: Disease monitoring: Plants must be Physical - slow sand filtration, Pythium diseases of greenhouse crops
Figure 2. Pythium crown and root rot in greenhouse cucumber showing orange discolouration of the crown area and rotted roots and root tips.
monitored for any signs of Pythium diseases throughout the cropping cycle. Remove and destroy severely infected plants and replant in new growing bags. Infected plant materials, including grow bags, must be safely disposed away from the greenhouse by deep-burying, incinerating or composting. Control fungus gnats (Bradysia impatiens) and shore flies (Scatella stagnalis) which spread Pythium.
Biological and Chemical Control Prevent Pythium diseases by practicing integrated disease management strategies based on cultural and biological controls. Use fungicides as a last resort at the onset of disease. Rotate registered fungicides with different chemical groups and strictly follow label directions to avoid resistance development in Pythium. Routinely monitor plants and evaluate the level of disease control if fungicides are used. Stop fungicide treatment and get professional advice if fungicides fail. Source Dr. Siva Sabaratnam, Plant Pathologist, BC Greenhouse Growers’ Association.
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IPM & greenhouse insect pests – scouting and record keeping
For some greenhouse farmers, IPM or Integrated Pest Management sounds like a repeat of an old adage. This critical subject however, is of such major importance to growers of fresh produce, flowers, berries or even cannabis that it needs to be repeated to ensure the industry at large applies it.
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ntegrated Pest Management in greenhouse crops and monitoring for pests is a critical step in quantifying potential damage that can be caused by a pest and aids in determining if intervention to control the pest is warranted. Scouting also helps growers determine the prevalent life stage of the insect or severity of the disease which is often critical to properly selecting and timing management strategies. Scouting for insect and disease pests involves monitoring the crop and cropping area for insects and diseases and also for signs, like visible fungal colonies, and disease symptoms, like leaf spots, and may include following a specific protocol to determine the incidence or severity of the disease. This important exercise includes looking for the insect at all life stages – egg, immature or adult – and attempting to quantify the population. It may also include inspecting for crop damage caused by the insect and setting traps to collect them. Growers should keep records of their scouting, including maps of their greenhouse, a record of sampling and pest pressure, as well as the control measures utilized including specific materials, rates and dates. Scouting should begin as soon as plants are placed in the greenhouse.
Tools for scouting Greenhouse assistants must be trained to use the following tools for scouting pretty useful: • Hand lens for inspecting small insects,
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mites, insect eggs or feeding damage. • White paper over which you can shake plants to count pest and beneficial insects. • Yellow sticky cards. • Coloured flags or wooden stakes to mark pest hotspots or spray treatments to crops. • Permanent marker to write scouting dates on sticky cards. • Camera/cell phone for taking pictures. • Containers for collecting plant, disease and insect samples. • Diagram of your facility made by hand or graphics program. • Reference materials for helping identify pests (find these resources at your pesticide/insecticide supplier). Methods for scouting In order to make the most out of time spent scouting, consider the following general recommendations • Section the greenhouse into manageable portions and scout them separately. Scouting a single range or bay at a time provides a methodical system to ease in recordkeeping. • Walk down available paths when scouting. Seek to inspect new areas or greenhouse benches each time. Re-examine hotspots weekly where you have recorded high pest populations previously. • Inspect 20 plants per 1,000 square feet of production space by turning over leaves, shaking the plant over a piece
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of white poster board and removing the plant from the pot to look at the roots, if the crop is highly susceptible to root pathogens. • Insert flags of different colours in pots signifying hot spots of each pest. Insert stakes in pots describing what each bay or plant grouping has been sprayed with: plant growth regulators, insecticides or fungicides. Consider placing indicator plants for each pest species or insect-spread virus in the greenhouse and check them once or twice a week: • Tomato, eggplant, lantana or marigold for greenhouse whitefly or silverleaf whitefly. • Marigolds, crotons, chrysanthemums, roses, impatiens and ivy geraniums for spider mites. • Peppers and fuchsias for aphids. o Gerbera, verbena or chrysanthemum for thrips. • Petunia or fava bean for impatiens necrotic spot virus or tomato spotted wilt virus. If using biological control with banker plants, inspect the numbers of insects on them weekly to ensure a sufficient population for your beneficial insects. What am I looking for? One of the hardest things to learn about scouting is how to pick up on the visual cues that something is damaging the crop. Damage can come in many forms. Consider the following signs of insect damage and disease:
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• Cupped, chloric, stippled, spotted or malformed foliage. • Any discoloured or damaged foliage or flowers. • Accumulation of insects. • Shed skins of aphids that look like dandruff. • Pockets of less vigorous or dying plants. • Anything out of the ordinary. Using sticky cards in the greenhouse, yellow sticky traps are utilized to capture pests. The index-sized cards should be placed at plant level. Follow these general guidelines to get the most benefit from using sticky cards: • Place a minimum of one sticky card per 100 square meters of production area. • Replace the sticky card weekly, recording the number of each type of insect per card. A common trick is to attach a tag or write the date the card was placed to ensure cards are replaced frequently enough. • Check the sticky card for the presence of beneficial insects if using biological control methods. Yellow sticky traps can be used to capture pests and are highly attractive to thrips, whiteflies, fungus gnats and winged aphids. Blue sticky cards are more selective and tend to mostly attract thrips. Sticky cards are not useful for detecting building hotspots of aphids or spider mites.
Recordkeeping • Create a diagram of your facility by hand or using a computer image created by a program like Google Earth. Mark hot spots of different pests with coloured tacks or stickers on paper maps or indicate them with different coloured marks on a whiteboard weekly. Next to the marks, write the date scouted to see where hotspots have moved in the greenhouse. • After gathering sticky cards, create a graph in a program such as Microsoft Excel where you can monitor populations, especially if using biological control methods. Ed: These are important and useful measures the greenhouse grower should train his manager and assistants in. It should be part of their daily routine and even become their lifestyle. This will inevitably pay off in the long run. The above editorial was compiled from various sources with in-depth knowledge and years of experience in greenhouse management.
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THE FOUR MOST OFTEN FOUND INSECT PESTS IN A GREENHOUSE Insects can be more than a pest. From tarnished appearance to disease spread, troublesome whiteflies, aphids, mites, and thrips can wreak havoc on your crop. Stay ahead of insect pressure and grow beautiful, marketable plants with an effective control program. Here is a list with pictures and description of the most often found insects in a greenhouse. Show these examples to your assistants in order for them to get acquainted with the looks of the insect and where on the plant to seek for it.
Whiteflies The greenhouse and sweet potato are the most prevalent whiteflies. It’s not uncommon to have every growth stage present – break the life cycle in two places, larvae and adult, to end whitefly invasion. Compared to the smaller, slender sweet potato whitefly, the greenhouse whitefly has wings that form a triangle. Sweet potato whiteflies must be tested for B- or Q-biotype.
Spider Mites Mites generally feed by piercing the underside of leaves. Scout often and watch out for a speckled or mottled appearance to the upper leaf surface, a telltale sign of mite invasion. Adult mites have four pair of legs, however just-hatched larva have only three sets. The male has a pointed abdomen and is usually smaller than the female.
Aphids Watch for aphids on and under tender new growth. Aphid populations multiply quickly, treat early with a fast and highly effective product to combat a rapid population boom. Aphids may be winged or wingless and feed with a piercing “beak” mouthpart. They are the only insects with cornicles (thorn-like tubes) on their abdomen.
Thrips Adult thrips are winged and can enter the greenhouse via contaminated material or by fly-in. These tiny pests hide deep within the plant, thus high-pressure, fine droplet sprays are suggested. Thrips can range from light brown to black in colour. Adults have four long-haired fringed wings that they hold flat to their back.
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Technological advanced
grow systems for leafy greens For anyone who cares about natural resources, it is not difficult to obtain research on the carbon footprint of food transportation and many other ways in which we harm the environment during the food production process.
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eing passionate about the environment and inspired after attending a hydroponics course presented by the late Ben Safronowitz, Cape Town couple Will & Lynn Gunning started NFT Hydro in 2015. It is now a well-established international brand. In 2015 they manufactured the first hydroponics kit systems available in South Africa, using their own bespoke designed hydroponics profiles, extruded locally. Since then, their offering has evolved to include semi- commercial kit systems for growing vine crops, leafy greens and micro-greens. These afford any new grower the ability to learn practically on one of their hydroponic systems, under the guidance and instructions of NFT Hydro. Their semi-commercial systems are sizeable enough for any new grower to start a fresh produce business and enter the market with superior quality hydroponics-grown produce, sustainably grown. At the same these semicommercial systems can be scaled up to
A fully grown spinach plant, well-rooted and grown in the NFT system. a commercial level of production over time. All the Gunningsâ&#x20AC;&#x2122; systems are locally manufactured by the company and can be adapted to suit the precise requirements of new growers or
commercial farmers. A commercial hydroponics set-up in a 10m x 30m greenhouse will offer 300 x NFT hydroponics profiles containing 8 640 plant sites (holes) for growing a
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Even growth obtained with the system. These plants are just about ready to be harvested.
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The system profile ends showing fertigation feed. variety of leafy greens. This allows the grower to harvest 4320 plants every 3 â&#x20AC;&#x201C; 12 weeks, depending on factors such as growing technique, crop type and methods of harvesting. Growers can decide to harvest the fresh produce either as living lettuce, with roots intact or harvest the leaves of the plant, leaving the plant in the system for longer. Depending on the climate of the country or area of the farm or production site, either shade net structures or plastic covered greenhouses are utilized for production with the NFT systems. Depending largely on affordability and the climate zone of the project, the system will function according to the
growerâ&#x20AC;&#x2122;s specifications. When climate procedure of scouting the greenhouse control and nutrient dosing systems are for any pests, using bright yellow or blue introduced, a slightly higher financial sticky cards to identify any early signs of investment is required, but then, higher pests being present in the greenhouse. yield and quality It is of essence that growers The main advantage fresh produce is of a greenhouse with have their greenhouse gained. climate control and attendants follow a daily Pest management nutrient dosing systems procedure of scouting the is essential in is that year-round any hydroponics greenhouse for any pests, production is possible greenhouse set-up. using bright yellow or blue allowing growers to One of the most sticky cards to identify any grow deeper into the crucial aspects seasons. early signs of pests being is air movement Minimal greenhouse present in the greenhouse. by utilizing fans staff is required to and wet walls. It run the greenhouse fitted with NFT is of essence that growers have their hydroponics systems and climate / greenhouse attendants follow a daily irrigation technologies. Two to three persons are enough on a commercial production site with several greenhouses for scouting plants, overseeing climate and fertigation, as well as nutrient dosing, water quality and general hygiene. At harvesting, additional part time assistants (with previous training and the necessary skills) are required. The pack house staff is employed on a temporary basis as well.
Water lettuce in the profile system.
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Since 2014, Will and Lynn Gunning have steered their business with a deepseated passion and diligence to suit every clientsâ&#x20AC;&#x2122; requirements according to his/her production intent and marketing strategy. Whether it is a first time or progressive grower or simply upgrading on existing systems, their experience and care taken in every transaction, after sales service and subsequent partnerships in the hydroponics industry breathes new air into undercover farming production locally and internationally. JS
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Improving cucumber yield with optimal drip fertigation
Well managed fertigation systems offer best results and even yield.
Production of greenhouse grown cucumbers can be increased by optimal drip fertigation management that improves yield, quality, water and nitrogen use efficiently.
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o establish reasonable water and fertilizer inputs is of great importance to improve crop yield, water and fertilizer use efficiency in a greenhouse. During an experiment the effect of different levels of irrigation and nitrogen (N) fertilizer on the yield, fruit quality, and water
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and nitrogen use efficiency of cucumbers under fertigation systems in a greenhouse was recorded. The least square method and multiple regression analysis were used to select the largest single target and multi-objective optimum in this study. The treatments comprised three drip irrigation levels (with ET0 as the reference crop evapotranspiration, W1: 60% ET0; W2: 80% ET0 and W3: 100% ET0) and four N fertilizer levels (N0: 0 kg/ha; N1: 180 kg/ha; N2: 360 kg/ha and N3: 540 kg/ha). Results revealed that the single factors of irrigation and N had an extremely significant effect on the yield. The fruit yield increased with the amount of irrigation water and reached 55.9 t/ha and 51.6 t/ha with the use of N 540 kg/ ha and 360 kg/ha, respectively. The
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yield of 49.6 t/ha, the highest water use efficiency (WUE) of 55.8 kg/m3 and vitamin C of 128.4 mg/kg were obtained from conditions involving medium irrigation levels (80% ET0) with the application of 360 kg/ha N. The highest soluble sugar content at 2.8% was achieved when the irrigation level was 60% ET0 and the application of N was 360 kg/ha. The nitrogen production efficiency (NPE) and partial factor productivity of nitrogen (PFPN) decreased with the increase in the nitrogen application rate. The highest NPE and PFPN of 263.4 kg/kg and 265.9 kg/kg were obtained from irrigation levels of 80% ET0 and 100% ET0, respectively. The yield response factor key of the cucumbers was 0.94. Taking into account the yield, quality, and water and nitrogen use efficiency, the irrigation level of 80% ET0 with the nitrogen level of 360 kg/ha proved to be the best fertigation strategy. Within a 90% confidence interval, it was concluded that when the irrigation interval was 124–151 mm and the nitrogen interval was 318–504 kg/ha, the yield, WUE, and Vitamin C reached ≥90% of their maximum values at the same time. The outcome of this research exercise is of great significance to the precision management of water and fertilizer in greenhouse produced cucumbers. By: H. Wanga and Y. Xianga, Science Direct.
ADDRESS: CODE: CONTACT NUMBER: Account Name: Nufarmer Pty Ltd t/a Undercover Farming Bank: First National Bank, Kolonnade Branch Code: 25 10 37 Account No: 62007699806
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