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Tailor-made solution for pest control in cut roses tackles thrips

The use of the predatory mite Euseius gallicus, commercialized by Biobest under the trade name ‘Dyna-Mite® G-System’ started in early 2014 in the Netherlands, Belgium and France. Biobest researcher Juliette Pijnakker is very satisfied with the steady progress of this biocontrol strategy in cut roses. “It’s a unique strategy and there are different reasons for its strong performance.” says Juliette. “Euseius gallicus is well adapted to roses and it can establish a strong population before the pest even appears with the support of our NutrimiteTM food supplement. Recent work shows there is yet another strong factor in favour of gallicus. Biobest researcher Dominiek Vangansbeke proved the capacity of the predator to tackle thrips at the egg stage. What’s better than taking out the pest even before it is able to do damage?”

An innovation with strong foundations in research
Recalling the history of the new development, Juliette explains that this species of predatory mite was found in 2011 in a commercial greenhouse on Rosa cv. Red Naomi. Extensive cage and field trials on roses were carried out in the Netherlands and Belgium. The predatory mite’s potential to control western flower thrips Frankliniella occidentalis and greenhouse whitefly Trialeurodes vaporariorum was well documented. It was also shown to contribute to spider mite control. “The real breakthrough came when Biobest introduced Nutrimite™, a food supplement based on pollen of the bulrush Typha angustifolia L. in 2013. With a biweekly application of 500 grams per hectare when pest pressure is low, Euseius gallicus reaches a density of 1 to 2 predatory mites per rose leaf. With A. swirskii it’s rare to even reach a level of 1 predatory mite per 3 leaves,” explains Juliette.

Dyna-Mite® G-System tackles thrips even before larvae appear
Thrips control is the main challenge for pest control in cut roses. A recent paper by Van Houten et al. reports that one Euseius gallicus eats 2.6 thrips larvae per day. The predator attacks the larvae of the first stage. New Biobest data now show that Euseius gallicus can also eat the eggs of thrips in rose leaf. Dominiek Vangansbeke explains the importance of this new finding: “Thrips deposit their eggs under the surface of the leaf which makes them difficult to access for predators. In some crops like sweet pepper, the leaf kind of “ejects” the eggs rendering them again more accessible, but that is not the case in rose. With our knowledge of the special structure of the mouth parts of Euseius gallicus, we presumed it might be able to access the thrips eggs on rose leaf just before the eggs hatch. This has now been experimentally validated. The graph below shows how a single Euseius on a leaf disc is able to consume the large majority of thrips eggs before hatching.

Figure 1: Average number of thrips larvae hatched from a rose leaf disc. Five western flower thrips females were introduced on a rose leaf disc. 3 days later thrips were removed and a single Euseius gallicus was introduced per leaf disc. After another 3 days E. gallicus was removed. Daily counts of thrips larvae were done during 7 days from the introduction of the mites.

Biobest Product Manager Macrobials Yann Jacques concludes: ”We’re getting great feedback from growers about the success of the strategy. With these new research findings elucidating the mechanisms behind the strong performance of E. gallicus, we gain important and new insights that will help us to further fine-tune our recommendations to rose growers and that may be quite relevant in other target crops as well.”

For more information
Biobest Belgium NV
Ilse Velden 18
2260 Westerlo - Belgium
T +32 14 25 79 80
F +32 14 25 79 82

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