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biological pest control

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Researchers have found three species of predatory bug in the Miridae family that can limit the establishment of the harmful predatory bug Nesidiocoris tenuis in tomato crops. “Omnivorous predatory bugs could potentially be a great help in biological pest control,” researcher Gerben Messelink says.

In recent years the bug Nesidiocoris tenuis has become a serious problem in tomato growing. Although it controls whitefly and tomato leaf miner, the insect causes so much damage to the crop that growers tend to view it as a pest rather than a predator. These Mediterranean plunderers puncture fruits and flowers and cause necrotic rings which lead to stems breaking off. They inhibit plant growth, resulting in deformed plants. Tips fall off and production stagnates.

“Tomato growers in southern Europe have been using Nesi to control Tuta absoluta for years,” says researcher Gerben Messelink of Wageningen University & Research’s greenhouse horticulture business unit in Bleiswijk, the Netherlands. “Various other predators such as nematodes and parasitic wasps have been tried as well, but Nesi appears to be the most effective. Southern Spanish growers therefore mainly see this creature as a useful predator.”

But things are different hundreds of kilometres to the north, where Nesi is a serious problem for Dutch tomato growers. Crop damage is severe and the predatory bug is difficult to control selectively. Chemicals also have an adverse effect on Macrolophus, a relative of Nesi, giving pests such as whitefly free rein and disrupting the whole biological control system in the greenhouse. What’s more, this creature develops faster than related species. “It is a thermophilic insect, so when the temperature in the greenhouse is 20°C the population is already growing strongly,” Messelink says.

Omnivores in a spectrum

To tackle this problem, in 2015 WUR teamed up with the growers’ organisation LTO Glaskracht Nederland and submitted a project proposal, “Pest control with omnivorous predatory bugs”. This public-private partnership launched in 2016, financed half by the Dutch Ministry of Agriculture and half by the private sector. The private funding for this project comes from the Dutch tomato, gerbera and rose growers’ cooperatives, Stichting Programmafonds Glastuinbouw (the Dutch greenhouse horticulture programme fund foundation) and Koppert Biological Systems.

“Nesi is a predatory bug in the Miridae family, just like Macrolophus,” Messelink explains. “Miridae are omnivores that not only use plants as food but also serve as predators. There are many different species of Miridae and they are all located in different places in this spectrum. One species eats more plant, the other more prey. Macrolophus is a predatory bug that is very pest-oriented and only causes limited damage to plants. Nesi, on the other hand, quickly causes a lot of damage but is also a good pest controller.”

Messelink and his colleague Ada Leman ran a greenhouse trial last year in which they investigated whether establishment of this insect in tomato is limited if a population of other bugs is already established in the crop. To determine whether Nesi also affects the densities of its relatives, controls with these bugs without the notorious predator were also set up.

Insect cages

The greenhouse trial was carried out in large insect cages with one tomato plant per cage: grafted Brioso plants with two stems. The effect was assessed using three types of new predatory bug, which the researchers brought in from southern Europe. “We investigated the effect these three species had on pest control and we looked at the development and establishment of these insects in tomato and their secondary effects on Nesi. The result was quite spectacular,” the researcher says. “Nesi was able to establish in all treatments, but what we saw was that where we had built up a population with the new species first before introducing Nesi, establishment was reduced by an average of 90%.”

The final population density of the predatory bug among its three southern European cousins averaged 85%, 92% and 95% lower than the controls respectively. There was no significant effect the other way round.

Whitefly and cotton whitefly

“We confirmed in the laboratory that the adults of the three new species feed on the young Nesi nymphs, but it is not yet clear what effect Macrolophus has on the insect,” Messelink says. “We have observed that Macrolophus is often squeezed out in the greenhouse, and in the laboratory too we have noticed that this bug doesn’t feed on young Nesi nymphs. So using these new species could offer an advantage over Macrolophus. But it’s important to find out whether they are just as effective in controlling the main pests.”

Now that the researchers have established that the three southern European bugs control tomato leafminer, this year they are looking into the effect these species have on greenhouse whitefly and tobacco whitefly.

Standing army

Messelink is enthusiastic about the initial result. “You have to view the predatory bugs as a standing army. If you can deploy the new species preventively, if they can control different pests, tackle Nesi and don’t damage the crops, then we will be taking a big step forward in biological control.”

At the end of the day, the researchers want to be able to offer growers a total package. “We are looking for a predatory bug that controls an infestation as effectively as possible and doesn’t damage the crop,” Messelink says. “I have high hopes. I think these insects will be a big help in biological control in the future.”

Experience in rose and gerbera

As part of the same study, the researchers also investigated the use of omnivorous predatory bugs in gerbera and rose. “We think that this insect can offer a solution in these crops too,” researcher Gerben Messelink says.

“Whitefly, caterpillar, Echinothrips – all these pests can be controlled with predatory bugs, so it is possible but we still need to do more research. We have observed that this insect has difficulty establishing in gerbera, mainly because of the mildew control technique that’s currently used. Growers spray the crop, and it is not so much the toxic value that eliminates the predator; research has shown that spraying under high pressure ‘blows away’ the predator. So if we can find another way of controlling mildew, we can also build up a population of predatory bugs in the crop and control pests that way.”

The researchers are also trialling building up a population of these predators in rose. “Rose is a woody plant, which makes it difficult for this insect to establish. Bugs prefer hairy, herbaceous plants. But we might be able to keep these predators in the crop by using a host plant, for example. We have already demonstrated that we can control Echinothrips in rose effectively this way.”


Three species of predatory bugs in the Miridae family can limit the establishment of their harmful cousin Nesidiocoris tenuis in tomato growing. Researchers looked at the effect they have on pest control. They investigated the development and establishment of these three southern European predators in tomato and their secondary effects on Nesi. The final population density of Nesi with the three predatory bugs tested was around 90% lower than in the control. It is likely that these omnivorous insects could ultimately also offer a solution in rose and gerbera.

Text and images: Marjolein van Woerkom.

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Predatory mites are the most important natural enemies used for biological pest control in greenhouse horticulture.

Many of these predatory mites are mass-reared on prey mites that feed on fungi growing on bran. In collaboration with companies in the Netherlands and Spain, we investigated whether predatory mites could also be reared directly with artificial diets based on insect proteins. High-quality proteins from sources such as black soldier flies and mealworms were found to be suitable food sources.

However, formulating these semi-liquid diets wasn’t easy as the predatory mites were unable to consume diets offered in microcapsules. The next step, therefore, was to focus on diets for prey mites. Several species of prey mites were reared on diets with different nutritional values. When administered on plants, the prey mites reared on high-protein diets produced predatory mite populations five times the size of those feeding on bran-reared prey.

These nutritious prey mites can therefore enhance pest control by quickly boosting populations of predatory mites.

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Supplementary feeding of predatory mites with a pollen preparation has outgrown the trial phase. A large number of growers is successfully using this method. While pest numbers are low, predators that also eat pollen have the chance to build up a vigorous population. Dutch growers Wesley Klauwi from sweet pepper nursery Zuidgeest Growers and cucumber grower Bart de Groot explain how they do it.

“Snack peppers are different from standard pepper varieties, and you have to learn to respond to that.” Wesley Klauwi is responsible for crop protection at Zuidgeest Growers, a nursery famous for its Vitapep orange snack pepper. “Caterpillars and aphids are the biggest problem at this nursery. We have the other pests well under control, even though we have had a lot of pressure from thrips here over the last couple of years”, he explains.
The sweet pepper nursery gained experience this year with supplementary feeding of predatory mites with Nutrimite, a preparation based on cattail pollen. It is highly nutritious for predatory mites and unattractive to pests. What’s more, this pollen doesn’t produce allergic reactions.

Spreading pollen

In the first week of January, Amblyseius cucumeris was used to control thrips on the four hectare site in Maasdijk (south-west Netherlands). A bag was hung on every twelfth plant, and Amblyseius degenerans was added two weeks later. The rows in the greenhouse are 50 metres long. Klauwi opened the tubes halfway down the rows. He then provided three to four batches of supplementary pollen at 14-day intervals.
He disperses the product with a small leaf blower, first around the places where he has distributed the A. degenerans and then around the whole greenhouse. “We want to see plenty of predatory mites round about March, and we have achieved that at all our sites,” he says.

Good results

Supplementary feeding of natural predators is becoming more and more popular. Marcel Verbeek of Biobest says that about half of his customers now feed pollen. The major advantage of this method is that it allows natural predators to develop well at a time when there are not yet enough pests to sustain them. Predatory mites in a sweet pepper crop can often survive simply on the pollen from the flowers, but a cucumber crop produces no pollen at all. This makes it much harder to build up a good population of natural predators.
Several predatory mites eat the pollen preparation, namely A. degenerans, A. swirskii and Eurseius gallicus. A. cucumeris also responds to the preparation but less vigorously than swirskii and degenerans. “We are seeing good results. Proponents are finding that it makes the predatory mites more active and more vital. Others believe that the mites can get lazy or that they would prefer to eat pollen than catch pests.” Verbeek doesn’t agree.
Sometimes it is hard to make a sound choice. The advice is to disperse a total of 0.5 kg per ha each time. Supplementary feeding is not cheap but it delivers good returns because of the increased numbers of predatory mites in the crop.

Resilient population

“We are certainly seeing plenty of Amblyseius degenerans running around on the flowers,” says Klauwi. “Thrips are under control and this predatory mite also tackles spider mite. We hope that Orius will help with pest control in around week 25.” They prefer the combination of A. cucumeris, A. degenerans and supplementary feeding with pollen. “As far as we’re concerned, supplementary feeding is the future.”
Verbeek: “Our advice is to build a resilient population of natural predators before problems start arising in the crop. Sometimes this even starts with the breeder. Some growers are already releasing predatory mites at the propagation stage as well as providing supplementary feeding with the preparation.”

Gradual start keeps down costs

“Supplementary feeding doesn’t come cheap,” says Bart de Groot, Aad and Ruud Zwinkels’ partner from Kwintsheul in the Westland area. They have been using the pollen preparation at the 28,000 m2 cucumber nursery for a couple of years now.
The cucumber growers plant three times a year. To begin with they release A. swirskii at a rate of one bag per four plants to control thrips and whitefly. When the first spider mite appears, they add Phytoseiulus. Although the preparation is very effective for the predatory mite population, they decided last year to take a more gradual approach to keep costs down. In April 2015 the pressure from whitefly increased and there were not enough swirskii present to tackle the problem, so they decided to start supplementary feeding again.
This year, the course of events is the same as in 2014. De Groot is using 0.25 kg pollen per hectare per week on this fast growing crop. “But we still notice that this is saving us a round of predatory mites,” he explains. “Incidentally, we don’t have a lot of trouble from thrips. It’s mostly whitefly that we need to keep under control.”

Fan is faster

The leaf blower they used for dispersing the preparation in the first two years has now been replaced by a fan on the pipe rail trolley as dispersing the pollen with the leaf blower took too long. The grower can now get the job done in 45 minutes. He does it early in the morning before the vents are opened. He positions the trolley so that the fan is about half a metre above the wire. Then he rides down eight rows in the 300 metre-long greenhouse. The following week he changes the pattern and takes the eight rows in between.
The advantage of this method of dispersal is that the grower gets a good picture of the condition of his crop in a short space of time. “It means I can see straight away whether the plants are growing well and if there are patches of whitefly, spider mite or other pests remaining.”

Combining bio and pollen

This year, biological control is once again going according to plan. When the third crop starts, De Groot will be using a high dose of standard bags of swirskii, one for every two plants. He wants to keep this population vital until the end of the crop with supplementary feeding.
“We are noticing that supplementary feeding with the pollen preparation is adding a new dimension to our biological control. We’ve seen for ourselves how predatory mites can build up a good population when they get a varied diet, in other words a combination of pests and pollen. With more and more chemical pesticides being banned, I see this as a good strategy for the future,” Verbeek adds.


The number of sweet pepper and cucumber growers feeding predatory mites pollen preparations is on the rise. The varied diet of pests and pollen creates a good, resilient population of natural predators. Although this strategy means the money has to be spent before the benefits are felt, this trend looks set to continue.

Text and images: Pieternel van Velden.

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The management of Koppert Biological Systems received a Royal Award on 15 September. Paul Koppert and Henri Oosthoek received the award from mayor Pieter van de Stadt. It was the culmination of a week in which the family company celebrated its 50th anniversary.

Both men were appointed Officer of the Order of Oranje-Nassau. One of the reasons behind both Paul Koppert and Henri Oosthoek receiving the award was their tenacity in creating awareness of biological crop protection across the globe. As well as leading the family business, Koppert and Oosthoek make a significant contribution to people in need. For example, they were the founders of the Christian Childcare Programme Foundation in Uganda, which has been helping disadvantaged children follow basic and vocational education since the early 1980s.

Experience centre opened by the King of Holland

Koppert Biological Systems celebrated its 50th anniversary this week with all its ‘partners in nature’. The highlight was King Willem Alexander's visit on Thursday, 14 September, when he opened the Experience Centre. Paul Koppert and Henri Oosthoek gave the King a tour of their company, where he learned about the use of insects, mites and microbiological solutions produced by the company in international agriculture and horticulture.

Standard bearer for Dutch horticulture

Koppert is a standard bearer for Dutch horticulture. In 2012, it won the first DHL Export Trophy, which is awarded to a Dutch SME company for distinction in export and innovation. The jury called Koppert 'An example for many companies in the Netherlands'. In 2016, Koppert was proclaimed winner of ‘The New Champions’ by the Financieel Dagblad newspaper. The jury stated that it is a ‘Fantastic fast-growing company that is making a sustainable contribution to solving the global food problem thanks to biological crop protection, and has great potential to shake up the microbiology market’.

Biological pest control now commonplace

The company, which started in 1967 with a type of predatory mite (Spidex) to combat spider mites, is now a multinational with 25 branches in 27 countries. Currently marketing more than eighty natural enemies against pests and diseases in horticulture, Koppert is achieving revenue growth of 12.5% every year (€ 160 million in 2015, with € 6.5 million profit). The company is a global leader in greenhouse horticulture, marketing useful insects, microbiological products (since 1980) and bumblebees for pollination (since 1988). Biological pest control for crops grown under cover has become commonplace worldwide. About 90% of the area used to grow cucumbers, peppers and tomatoes is treated biologically and pollinated with bumblebees.

Expansion in other sectors

Koppert is now expanding its empire into other sectors, such as open-air cultivation and animal husbandry. In 2012, Koppert acquired Brazilian company Itaforte, a producer of microorganisms, giving it access to the market for large-scale open-air cultivation of crops such as soya, sugar cane, corn and wheat. The challenge now is to introduce new products that can increase plant health and yield, despite the narrow margins. One example is Panoramix, launched by Koppert in 2015, a seed coating that encourages seedlings of large arable crops. Microorganisms and amino acids must ensure that crops such as wheat and corn can absorb nutrients like nitrogen and phosphate. For the livestock market, Koppert introduced a predatory fly, a natural enemy of stable flies, which can be used with pigs, chickens and cows. Koppert also introduced a predatory mite to control blood lice in both livestock and laying hens.

The Global Market is Open

There are now thirty companies operating in and from the Netherlands, including Bayer Crop Science, Certis, Biobest, BASF and Syngenta, which are active with biological pest control, pollinators and microorganisms. Koppert is the market leader in this sector thanks to its fifty-year lead. In 2016, sales were € 182 million, with the company employing 1,213 FTEs. Net profit last year was € 12.3 million. Koppert has 25 branches in Europe, North America, South America, Northern and Southern Africa, Russia, China and India. The company employs 400 consultants who help customers introduce biological pest control, bumblebees and microorganisms. Until 2000, sales were largely dependent on vegetable crops, but now seed companies, fruit farmers, flower growers and arable farmers are also important customers. Another big market is up for grabs. According to Paul Koppert, "Our development as a company has only just started."

Text: Mario Bentvelsen. Photo: Koppert Biological Systems.

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Vegetable growers don’t like to admit that they have mealybug. A group of cooperating parties therefore sent a questionnaire to growers in 2015. From this it appears that mealybug is a tricky pest to control and it is becoming increasingly prevalent in vegetable production, especially in tomatoes, sweet peppers and eggplants. The method of control varies. A clear-cut biological strategy is still lacking. Various companies and research centres are now working on effective, affordable control methods.

Mealybugs live on plant sap and tend to live in colonies. Due to their uptake of so much sap plants can loose vigour. The pests often live on the fruit, in the axils of the stems or at the base of the plant. For example in sweet peppers they live under the crowns of the fruit and in tomatoes often initially at the base of the plant, in the clips and low on the stems.
Growers often overlook mealybugs because they hide themselves so well in plants axils or in the greenhouse construction to escape their natural enemies and/or difficult environmental conditions. Only during peak periods do they emerge on mass.

Males and females

Adult males and females differ greatly in appearance. Adult females are covered with a protective waxy layer, usually have legs, no wings and are 0.4 to 0.8 mm long. The sexually mature females produce a sex pheromone to attract males.
Fertilized females lay hundreds of eggs, usually in an egg sac that consists of a white fleecy mass. This protects the eggs from predators, pathogens, drought and excessively high air humidity. The eggs also hang more easily on the plants in these egg sacs. After laying the eggs the females dry out. Unfertilised females and fertilised females that are overwintering can survive for several months. Female mealybugs go through five developmental stages: eggs, three nymph stages and the adult stage. The optimal conditions for the development of mealybugs are 26ºC and 60% humidity. Each stage takes six to 16 days. Adult males are winged and are about 1 mm long. They don’t have any mouthparts and therefore cannot feed. They survive only a few days to mate. The males go through six development phases as they mature to the adult stage.

Grower survey

In 2015 Biobest and growers association LTO Glaskracht Nederland looked closely at the problem. They contacted growers and crop protection advisors and invited the growers via the organisation’s website to complete a questionnaire about their experiences with mealybugs and how they deal with the problem. In total 89 growers answered the questions of which 43 grew tomatoes, 25 sweet peppers, seven aubergine and seven cucumbers. In addition, they visited ten growers. Specimens were collected and identified by a European specialist at species level.

Two types

Two harmful species were identified: Pseudococcus viburni in sweet peppers, eggplant and tomato and Phenacoccus solani at a sweet pepper nursery.
P. viburni is the most common species found in Dutch greenhouse vegetable crops. This originates from neotropical areas. Under greenhouse conditions development takes one to two months. This species can easily survive the cold and overwinters mostly in the first nymph stage in bark or in the ground.
One pepper grower also discovered P. solani. It is the first time that it has been found in a Dutch greenhouse although this species is prevalent worldwide. It is a major pest in sweet peppers in Spain. At first glance it seems to be whiter than P. viburni. This type is polyphagous and can settle on more than 30 plant families. This mealybug develops in 15 to 33 days at a temperature between 20 and 30ºC.

Found year round

One of the questions was whether growers ever had or still have trouble with mealybugs. The survey showed that this pest occurs in the greenhouse the whole year round if its spread is not stopped in time. Just 40% of the growers who answered the survey managed to eradicate the pests. On a few nurseries the pests spread so much that it was impossible to bring them under control using the usual methods.
The problem is the greatest in tomatoes. Of the 43 participating growers 19 had suffered problems and it is was still present on 11 nurseries. Of those participating in the survey the area infected with mealybug rose from 7 ha in 2013 to 10 ha in 2015.
Infected plants return about 10% less. Growers certainly waste just as much money searching for and controlling the pest.

Control methods

Good hygiene measures and identifying the problem on time remain the first steps of control. Growers appear to be very creative at identifying and monitoring the mealybug. They reduce the infection by steaming the sub-surface, burning the infected stems, and using insect glue on substrate slabs and the greenhouse structure.
Most growers control the problem locally. Growers that suffer problems year round blanket spray two or three times when the young plants arrive. On these nurseries new colonies continually appear even after the entire greenhouse has been disinfected. The females escape the control and hide in the greenhouse structure (often next to the meter cupboard). Young larvae, the crawlers, are immediately seen on the young plants.
Many growers use the neonicotinoids Calypso or Gazelle with strong wetting agents to improve the control. The mealybug hotspots are sprayed two to four times after each other with an interval of four to seven days, depending on the level of infection. The old hotspots are checked every four weeks.

Gap in a strategy

A clear biological control strategy is not yet available. The survey shows that experiences with biological pest control are still very limited and the introduction of natural enemies are often too late and carried out with too few predators. Vegetable growers prefer to use biological solutions to limit residue on their products, but this approach needs to be effective. Natural enemies and green pesticides will play an important role in an integrated approach in future.
Various researchers from companies and research institutes are working on the problem and hope to be able to offer effective and affordable methods to growers as soon as possible. Biobest is experimenting this year with predators. Larvae of Cryptolaemus (ladybirds) and lacewings seem to have potential. They can clean up the first hotspots, but the biological strategy has yet to be fine-tuned into affordable solutions for growers.
Several parasitic wasps have also been reported some of which are available commercially. However, these do not offer a solution in the short term.

Practical advice

Based on the survey, a literary review and practical experiences, it is meanwhile possible to provide advice on how to prevent the development of mealybug or to slow it down.
1. Hygiene
Spray the infected plants and contaminated areas before the change of crop three to four times with a neonicotinoid combined with a super wetting agent and/or remove infected plants and dispose of them in rubbish bags. Remove the old crop and plant remains. Disinfect the ground and substrate. Clean the entire greenhouse with formalin or hydrogen peroxide and disinfect materials. Renew the substrate annually. Properly inspect plant material when in arrives at the nursery.
2. Scouting and monitoring
Detect the first mealybug areas fast. The pests hide in crevices and cracks under cloths, slabs, gutters, gutter edges and between pipe rail supports and greenhouse pillars. Inform and instruct personnel. Mark the infected plants and contaminated trellis with tape. Use yellow sticky traps with sex pheromones to attract the males.
3. Physical control
Remove infected material; pick leaves (pick the stem bare). Spray with soap or an oil.
4. Spraying
Control is a matter of patience, monitoring and persistence. The crawlers are easy to kill but the adult females are difficult to control with insecticides because of their protective waxy layer. For good, long-lasting control it is recommended to use a broad action substance that works against mealybug. Take note: this should not be used with natural predators. Substances with systemic activity via the plant sap are usually more effective. Spray frequently because the hot spots often return in the same place (blocks of three sprays with a 7 to 14 day interval, repeat after six weeks if necessary). Spray the stems well. Mealybugs often take cover in the axils. Use a wetting agent to ensure good contact with the pests and their waxy layer. Use a lot of water.


Mealybug is an increasing problem in greenhouse cultivation. A stocktake in 2015 highlighted two common types. Growers address the problem in various ways: hygiene, spraying, a mechanical approach (burning, glue, brushing away) and the use of natural predators. However, these control methods are not enough. Further research is being carried out.

Text: Marleen Arkesteijn, Juliette Pijnakker and Joke Vreugdenhil
Images: Marleen Arkesteijn and Biobest

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Spain is – perhaps wrongly – still often seen as a country with middle-tech greenhouse horticulture: that is crops grown in the open ground, only protected by plastic stretched over wooden poles and the sun, however positive, as the most important growth medium. However, that is changing. In southern Spain more and more growers are switching towards professional vegetable cultivation in high-tech greenhouses.

Agrosol Export, of Roquetas de Mar, Almería, is one of those Spanish growers which has invested heavily in climate control, water utilisation and is introducing organic production to ensure year round harvest of quality produce. Founded in 2008, the company is owned by three families and run by eight members of the second generation. Ambitious and knowledgeable in production and marketing, they decided that their future lays in large scale, high tech greenhouses.
“Our fathers were growers and our families have been involved in agriculture in the area since the 1960s. We realized that if we could provide our clients with the same quality all year round we would be more competitive than other local Spanish producers and our traditional competitors in Tunisia and Morocco. We made significant investments in 2008 in high tech greenhouses and then again in 2012 when we installed heating pipes and CO2. At the moment we are very satisfied although we do have plans to expand further,” says José Ángel Amat, one of the directors.

Change the assortment

They have 105 hectares, including 32 hectares of state-of-the-art greenhouses, equipped with double layered plastic between which air is blown, to give a very good thermal insulation.
Initially they grew cherry, beef and snack tomatoes but one of their advantages, says Amat, is that they can change the assortment to respond to the market and client demand. “For the first four to five years 60% of our production was cherry tomatoes but over the last two years that has decreased as many other growers now grow cherry tomatoes. That changed the market. We want to be as profitable as possible per square metre so we switched over to mostly sweet peppers and cucumbers.” At the moment 50% of the greenhouses produce bell peppers, 45% long cucumbers and only 5% (8 hectares) is tomatoes.

Year-round consistency

Another change was the installation of pipe rail heating on 15 hectares in 2012. Various types of heaters warm the air in a further ten hectares. You’d think that heating pipes would be superfluous in southern Spain but after a visit to Mexico Amat says he realised their potential. “You can’t imagine the level of high technology they have there. They have pipe rail heating and I was very impressed with the quality of the fruits they were able to produce. Here the minimum temperature in winter can be 6-7ºC and at that temperature the yield of bell peppers and cucumbers decreases. And we have high humidity in the morning which has a big impact on quality.”
Therefore, in 2012 Agrosol Export commissioned the Bom Group to install a methane-fired 12 MW boiler, a heat storage tank of 3,000 m3, pipe rail heating on 15 hectares and a CO2 system in the greenhouses and at a cost of 2.5 million euro.

Further expansion

“We run the boiler, which also provides CO2, from the end of October until the spring. This year that was until the beginning of May. This has enabled us to achieve consistently high yield of very high quality. We will harvest until the beginning of August and we expect to reach a yield of 20 kg peppers/m2; 70% red and 30 % green," says Amat. The cost price is around 0.80 to 0.90 euros per kilo, compared with 0.50 euros in the hot air heated greenhouses where the yield is somewhat lower at 7-8 kg/m2.
The benefit gained from the pipe rail heating means they are gradually installing more in the current greenhouses and next summer they plan to build a new 10 hectares high tech greenhouse. “If that goes well then in about three years we may build again,” adds Amat. “We believe that investing in technology is the only way to be better than our competitors.” The new house will also have a double plastic covering but they will aim to allow in more light and it will be higher, at 7 metres, to improve air circulation.

Direct marketing

Their success can also be attributed to their marketing and relationships with their clients. Most growers in the area sell through a cooperative whereas Agrosol knows its clients directly. Its main customers are UK retailers, although it does sell snack cherry tomatoes under the brand ‘Cherrytos and co' aimed at children. These are mainly sold through Faborit, a trendy outlet in Madrid, or via e-commerce. “We want to invest a little more in the snack tomato business because we think this is a good way to gain more profit,” says Amat.
Of course they have to fulfil individual audits for their clients such as Nurture for Tesco, and comply with codes of conducts such as GlobalGap and Leaf Marque but that is part of the commitment required for these partnerships.

Trend to organic

They are also increasing the volume of organic production. “Nearly 10% of crops are organic and we are planning to increase this in future to meet the growing trend.”
In the remaining houses they use an IPM program and biological pest control suggested by their supplier Koppert Biological Systems. They have been implementing this since they started Agrosol Export and their father’s used it before that.
This allows them to minimise most of the common diseases and keep well below the mandatory maximum residue levels. “We have a highly developed pest control system which allows us to avoid a lot of diseases,” says Amat. They currently include a range of natural predators including Amblyseius swirski, macrolophus, orius and Amblyseius californicus. “We do a control at the propagator and we make continual checks at all stages of the crop to check for disease and to ensure the natural predators are well established.”

Cocopeat substrate

Over the last few years they have been gradually switching to a cocopeat substrate. Now the majority of crops are grown in this, just some in rockwool. “We separate the cocopeat from the plastic bag and recycle them both: the cocopeat is composted and we are building a plant to convert the plastic bags into biodiesel for our own use.” It should be completed within six months.
“Our strategy now is to progressively convert all our greenhouses to high-tech, in a sustainable way. This is the only way to produce high quality fruits year round and be profitable per square metre,” the grower concludes. “It is a major investment but the results are good. Our clients are very happy with our service and our ability to offer quality products during the difficult winter times.”


Significant investment in high tech greenhouses, including pipe rail heating, by large Spanish grower, Agrosol Export, is allowing it to produce consistently high quality peppers and cucumbers year round. The majority are sold to UK retailers. It has the flexibility to switch crops to market demand and is gradually cultivating more and more organic produce.

Text: Helen Armstrong. Images: Agrosol Export

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Researchers and companies are continually developing new techniques for greenhouse production. Therefore, in principle crop protection can reach a much higher level. But to achieve this, all these techniques need to be integrated. A system has been developed within the Gezonde Kas (Healthy Greenhouse) program that links them all together.

Gezonde Kas is a large Dutch-German project comprising 10 research institutes and 22 commercial companies. It was completed in the middle of 2015 and achieved its goal: The development of an innovative integrated crop protection system. The different parts of the system alert the grower to the presence of pests and diseases, even before any symptoms are visible. The system then helps the grower to make decisions. Furthermore, the system suggests measures that are based on the use of as few chemicals as possible.
Many of the techniques were known already but during the project were adapted for use in practise, geared to fit one another and integrated into one system. This has, to a large extent, been set up in a trial greenhouse in the research centre, Versuchszentrum Gartenbau, Straelen, Germany.

Ready for translation

Project leader Carolien Zijlstra, of Plant Research International (part of Wageningen UR, the Netherlands), is a molecular biologist by origin. “At PRI we have the capability to identify crop predators based on DNA or proteins. We need just one fungal spore to detect the problem at an early stage. But the method needs to be converted for use in practise. That was one of the reasons for starting this project. And, in fact, many more methods are ready for translation,” she explains.
The Interreg IV-A project is financed by the EU (EFRO), the Dutch and German Governments as well as businesses. The new system consists of four process steps. For each of these, suitable methods have been developed for use in practise. “They have been developed for large innovative nurseries but parts of them can be used by every grower,” she says. “Growers can purchase all these products or choose from the possibilities.”


Step one is called Gezonde (Healthy) Start. “Just before the start of the crop you check the surroundings and materials to make sure they are free of pests and diseases and take preventative measures to avoid contamination,” says Zijlstra. The Luminex-test shows exactly if seed, plant material, water or substrate contain pathogens. “The system works with very tiny balls that are coated with antibodies or DNA. If a pathogen is present the coating binds with its protein or DNA. If that happens the tiny balls light up under a laser beam and you know which pathogen is present. You can test for a hundred pathogens at the same time.”
It's impractical to test all the plants in the greenhouse, so pre-screening with another technique is useful to highlight the potentially infested specimens. This is made possible with a chlorophyll-fluorescence camera (see below).
This first step also contains two disease-suppressing measures: Firstly a top layer on the substrate ensures that predatory mites become better established and therefore can better attack thrips. Secondly, disease-suppressing substrate reduces the risk of contamination by Sciaridae by 80%.

Spore collector

The second step consists of advanced monitoring. This can be on a macro-scale; the whole greenhouse, or a micro scale; plant- or leaf level. Several techniques are available for both levels. The chlorophyll-fluorescence camera (CF-camera), for example, passes over all plants and assesses whether photosynthesis is being carried out properly. If not, it can be an indication that plants are contaminated. The multi-spectral image sensor is another method for detecting suspicious spots in the crop but uses a different technique. It sees better than the human eye.
Other techniques that detect on a macro level are the electronic nose and the spore collector. The latter collects air-borne fungal spores which are later analysed. “If you discover contaminated areas with the macro screening you can analyse them further using the micro scale techniques,” says the project leader. For example, the previously mentioned Luminex-test is very suitable, but there are other methods that can detect diseases present in the plant, such as TaqMan- or a LAMP-test. The Nsure plant vigour test indicates whether specific genes in the plant are turned ‘on’ or ‘off’. This indicates if the plant is diseased or not.
In the meantime the wireless sensor network keeps a check on climatic differences, in case something needs to be altered here.


“With this combination of steps you highlight diseases which you can’t yet see with the naked eye. The CF-camera notices if the plant is in trouble while, visually, nothing appears to be wrong. Then by implementing the other tests you can figure out what it going on. Also the vase life of flowers can be predicted with such a camera,” she says, describing the advantages of the new technology.
The disadvantages are the costs: the CF-camera currently costs around Euro 100,000, and it’s the same for the electronic nose.
After the problem is detected a decision has to be made. The third step in the process involves interpretation of the data and giving advice. Various decision support systems are available for this. The Climate Vitalizer gives advice on achieving a more homogenous greenhouse climate. Notify Me predicts crop development and a further three systems can analyse the risks of Botrytis and pest insects as well as propose control measures.

Precision spraying

These measures fall within process step four and relate to better climate control and pest management. The preferred method is a non-chemical approach. The project has developed a new strategy using endophytes, which improve the effectiveness of biological pest control. “Various natural predators eat both the pest as well as the plant. If you supply the plant with an endophyte – a useful microorganism that lives in the plant – the plant becomes less attractive to the natural predators and so these focus more on the harmful organisms,” says Zijlstra.
One of the most important parts of the project is the development of precision spraying. Cameras on the spray robot “see” the chlorophyll and only spray the plant and not the ground or into space. This saves 50% of the crop protection product. The next step is to combine it with the CF-camera. This detects firstly the suspicious areas so the robot only needs to spray these areas. This can save up to 70% of the product use.
The project Gezonde Kas has come to an end but a follow-up project for pot and container cultivation (tree nurseries) is in the pipeline. Researcher Zijlstra hopes that growers and horticultural advisors will quickly pick up on the techniques that have now been adapted for use in practise.


The project Gezonde Kas (Healthy Greenhouse) has developed an innovative four-step system in the field of crop protection. Key words are prevention, early detection, better control of climate and disease development and a reduction of chemicals. In all cases innovative techniques have been made adapted for use in practise and are described in this article.

Text: Tijs Kierkels. Photos: Wilma Slegers