The Swiss company Magnin, member of a Swiss coop, added strawberries to its range of vegetable crops in 2008. They currently have about 1 ha of strawberries, both under glass and in open field. Crop manager Sylvain Lappe had worked with biological control in vegetable crops and was determined to do the same on strawberries. He went through some ups and downs in the first years, but together with Biobest advisor Julien Mourrut-Salesse he persisted and now he’s quite satisfied with the results of the predatory mite A. swirskii in combination with NutrimiteTM. Sylvain is happy to share this experience with other strawberry growers.
With Western flower thrips (Frankliniella occidental) being the most significant pest problem, Sylvain initially relied on the predatory bug Orius laevigatus in combination with a single release of the predatory mite A.swirskii. Orius is well-known for its aggressiveness against thrips. The success of Orius in fruit crops depends on a number of specific circumstances, but the approach worked well for Sylvain. Then in 2010, a secondary pest suddenly became more important. Its name: Liocoris tripustulatus, a newcomer in the Geneva area. Biocontrol agents were not available against Liocoris and hence chemical intervention was necessary.
“The problem is that Liocoris belongs to the same insect group as Orius”, says Biobest advisor Julien Mourrut-Salesse. “Every chemical that controls Liocoris also hits Orius. A thrips biocontrol strategy built on Orius was therefore no longer an option”.
In the absence of Orius, Sylvain and Julien decided to work with swirskii only, increasing the number of releases to achieve high predatory mite numbers. “We’ve been working with swirskii for four years now,” says Sylvain. “In contrast to Orius, the swirskii mites are much more resistant to the chemical treatment that we need to use against Liocoris. The population drops a little bit after a treatment, but they rebound and continue to control thrips. Moreover, they catch thrips on every part of the plant – also on the fruits. ”
This season Sylvain included Biobest’s latest innovation in his biocontrol scheme. He applied Nutrimite™, a 100% natural food supplement made from a special selection of pollen and designed by Biobest to stimulate predatory mites. Sylvain: “We wanted to use swirskii in a real prevention strategy. Our goal was to build and maintain a large swirskii population before the first thrips even arrived. We started releasing the mites around the end of March in the greenhouse. Swirskii often faces a food deficit when there is neither prey nor sufficient strawberry pollen around. We provided Nutrimite™ to cover the food deficit. The number of swirskii mites after the application of Nutrimite™ was three to four times higher than before, also on the fruits.”
Sylvain is fully convinced about the contribution of Nutrimite™ to the success of his IPM strategy. “It helps us maintain a strong army of swirskii mites at all times: during periods of low thrips presence and/or shortage of strawberry pollen. Also it secures a quick population rebound after a chemical treatment to control Liocoris.”
“We used 500 grams per hectare, every 15 days”, Sylvain continues. “It takes no more than 45 minutes to blow the pollen on one hectare. We applied the powdery substance with a Makita blower extended with the special Nutri-app provided by Biobest. We are used to control powdery mildew on our fields with sulphur powder, so it didn’t cost us a lot of effort to incorporate this in our routine operation schedules – however, we don’t mix sulphur and Nutrimite™, we apply them separately.
“This strategy is really important to guarantee a product free of chemical residues”, concludes Sylvain. “Strawberries have an image as a really healthy product. Retailers and consumers want us to deliver a product in line with this image. We harvest two to three times a week, so a solution like this that helps us reduce the number of chemical applications is very important for us.”
The Magnin company, owned by Philippe Magnin and part of the cooperative Union Maraîchère de Genève, is based in Lully, near Bernex in the French-speaking part of Switzerland. In the past the company focused on cucumber and tomato cultivation. Since 2008 Magnin produces strawberries of a unique variety: Mara des Bois. This is a French strawberry that is well-known for its intense taste.
Nutrimite™ is a specially selected pollen type with high nutritional value for predatory mites. It’s being used in a growing number of crops to boost population development of predatory mites. In particular it works with predatory mites that can feed on pollen. For example, populations of A. swirskii grow explosively when they’re being fed with Nutrimite™ on a two-weekly basis. Within a few weeks one will observe exceptionally high predatory mite population levels in the crop. No need to worry about Nutrimite™ promoting the development of thrips. Nutrimite™ is unattractive for both Californian and Echinotrips. The strong predatory mite population guarantees better control!
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