Kaolin, lime and rock dusts to control Drosophila suzukii

The spotted wing drosophila, Drosophila suzukii, is an invasive pest in Europe and North America, infesting various soft-skinned fruits. Because D. suzukii attacks ripening fruits shortly before harvest, only insecticides with short pre-harvest intervals can be applied. Alternatively, kaolin, lime and rock dusts are non-toxic to non-target organisms, but the whitish coating on fruits potentially deters oviposition of D. suzukii. Therefore, we tested oviposition deterrence and insecticidal effects of such substances. Female D. suzukii flies were exposed to treated blueberries under laboratory conditions for 24 hours. Kaolin, linoptilolite, clinoptilolite + Heliosol (pine-oil based wetting agent) and calcium carbonate significantly reduced oviposition,whereas calcium hydroxide only had a marginal effect and diatomaceous earth had no significant effect. None of the tested products had an insecticidal effect. Kaolin, lime and rock dusts are therefore a promising tool to reduce damage of D. suzukii in softskinned fruits.