Whitefly is and remains a pernicious pest for growers of tomatoes and other crops. This is further aggravated by the fact that there are almost no effective chemical products that slot neatly into a biological control system. Roots Growers, producer of mini vine cherry tomatoes, gained experience with Koppert’s biological insecticide Mycotal. ‘We want our cultivation to be as organic as possible, and we’ve seen how Mycotal really helps us to achieve that.’
So says Sam van der Knaap, who is responsible for cultivation and plant protection at Roots Growers’ Honselersdijk site in the Netherlands. Located along Zwethlaan, the company’s headquarters has two sections: one covering 7 hectares (crops without artificial lighting) and another covering 8 hectares (crops under artificial lighting). The second site, located in Zevenhuizen, covers 11 hectares.
As organic as possible
Roots Growers grows the Piccolo variety, a mini vine cherry tomato. In this segment is plant protection in particular a crucial factor. ‘We obviously want our cultivation to be as organic as possible. It has to be, as there’s only one chemical product against whitefly in tomato that is effective and, unlike other products, also has a low MRL, which is a requirement for small cherry tomatoes. However, as we can only use this product a few times a year, we have very little leeway in terms of spraying frequency. We therefore need to leverage the full potential of biological plant protection.’
To combat greenhouse whitefly, Roots Growers uses Koppert’s Enermix (the parasitic wasps Encarsia formosa and Eretmocerus eremicus) and the predatory bug Mirical (Macrolophus pygmaeus) as well as Koppert’s Rollertraps.
Higher level of infestation
The two sections in Honselersdijk operate differently. The 7-hectare section grows crops without artificial lighting from week 2 to week 51 inclusive. The other section, fitted with SON-T and LED lamps, grows crops from week 34 to week 31 inclusive. ‘It never gets cold in there, so the level of infestation is higher and whitefly levels are high earlier in the year. We could theoretically spray everything in the greenhouse to death during crop rotation, so that the new crop starts off “clean”. But given the lack of effective products, that’s not an option.’
Halting whitefly development
Last year, Sam talked to Koppert consultants Alex Taal and David van Dijk and decided to compare the effectiveness of three biological products against whitefly. Among the products, which were sprayed almost weekly, was Koppert’s Mycotal.
The test produced good results. He explains, ‘It’s too early for definitive conclusions. We need more than one season of tests and analyses. That said, I did notice that the whitefly’s development cycle had clearly been inhibited in the spots treated with Mycotal. We used the same dosage of Enermix in the three test plots, and slightly higher dosages of the predatory bug. As a result of that choice, we’ve yet to find out how much of the effect can be attributed to Mycotal.’
Greater peace of mind
Nevertheless, Sam is adamant that Mycotal has helped to combat greenhouse whitefly. If Mycotal inhibits the pest’s development cycle, this increases the effect of the parasitic wasps and predatory bug. ‘It goes without saying that Mycotal’s biological nature is a big plus, as it means we can use it almost indefinitely and the whitefly can’t develop a resistance to it. That gives us greater peace of mind. These are good enough reasons for him to continue with Mycotal. And although the level of infestation is lower, he will also apply Mycotal in the unlit crops this year.
Improved Mycotal still the best product
In recent years, we have been focused on improving our biological insecticide Mycotal. Our commitment has paid off: the product is now even more effective and the shelf life has improved. Mycotal’s improved effectiveness means that it not only combats whiteflies even better than before, but RD studies proofs that it can also efficiently controls a range of other pests such as thrips, aphids and mealybugs. We are working to get these new targets approved on the label. In several independent studies, Mycotal has been and continues to be the most efficient product on the market.
Instead of conidia, we use blastospores from the fungus Lecanicilium muscarium Ve6 in Mycotal. Blastospores are the spores that are usually formed as a means for the fungus to spread and reproduce inside the insect. Mycotal’s blastospore formulation has a range of benefits: the fully sealed production means the final product is always free of contamination; the product gets to work faster, and it is even more effective at killing off pests.
Longer shelf life
We were also able to increase the shelf life of Mycotal by adjusting the production process. We are currently working with our registration department to put this improved shelf life on the label.
Another advantage is that blastospores germinate faster than conidia, and are also more effective in killing off pest organisms. As a result, the effects of spraying are visible sooner. As the active fungus in Mycotal is cold-tolerant and works at temperatures starting at 5°C, it can be applied effectively even at lower temperatures.