Thrips and spider mites are major pests in Vietnamese crops. Farmers still heavily rely on chemical pesticides for their control, negatively affecting the environment and human health. It would be more sustainable to adopt an "integrated pest management" approach in which predatory mites (Phytoseiidae) suppress the pest, with pesticides being applied as a back-up. As many pesticides can negatively affect predators as well, it is crucial that predator and pesticide are well-matched. The project will screen local pest and phytoseiid populations for pesticide susceptibility (phenotypically and

genotypically). Next, we will nominate a selection of "reduced-risk" pesticides that effectively kill the pests, yet with minimal negative effect on the predatory mites, or for which variability in susceptibility (=opportunity for selection) was observed. We aim to create phytoseiid strains with improved resistance to the selected pesticides via (marker-assisted) selective breeding of local strains, and to elucidate the underlying mechanism by a state-of-the art genomic approach. We will test whether these phytoseiid strains are still effective predators of spider mites and thrips, both in laboratory and (semi-)field experiments. This project will contribute to plant health both directly and locally, via an IPM approach for thrips and spider

mite control in Vietnam, as well as indirectly and globally, via increased knowledge on resistance mechanisms in phytoseiid

predators and their prey