Efficacy evaluation of particle films as oviposition deterrent against <i>Drosophila suzukii</i> in Austrian vineyards

Abstract

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is a polyphagous invasive vinegar fly. Females can penetrate certain soft-skinned grapevine varieties with their strong serrated ovipositor to lay their eggs within berries, which eventually leads to the decay and collapse of grapes. Alternative pest control options were tested in practically oriented field trials set up in two vineyards in Styria. The effect of the mineral particle films diatomaceous earth, kaolin and muscovite mica was compared to an untreated control. All products were complemented with wetting agents to increase the efficacy and/or the rain resistance of the film. Due to the long waiting times after application in organic production, only some of the trials also comprised a comparable insecticide variant (Spinosad). Treatments were applied from the beginning of infestations until harvest, and berries were sampled once to twice a week, depending on pest pressure. Evaluation of treatment effects was based on a microscopic analysis of berries for oviposition and a visual evaluation of the clusters. Both kaolin and diatomaceous earth led to a statistically significant reduction in oviposition and to a significantly improved macroscopic appearance of clusters compared to the control, whereas the effect of muscovite mica was negligible. A direct comparison of particle film and spinosad treatment was only expedient in one experiment, and in this case, the effect of kaolin on oviposition was significantly superior. Kaolin and diatomaceous earth might complement established integrated pest management practices against Drosophila suzukii and contribute to the reduction of chemical plant protection agents in the future.