Increasing efficacy of thrips chemical control with attractive additives in strawberry
Abstract: Insecticide treatments against thrips in strawberry cropping are often insufficiently working in the field, while in (extended) laboratory tests the same chemicals show high efficacy. An inadequate spraying technique, avoidance and cryptic behaviour of the thrips are possible explanations. In open field strawberry cultivation spraying technique is often underdeveloped, resulting in poor spray coverage. Attractive additives can lure thrips from their difficult to reach hiding places onto the treated plant surfaces, increasing the insecticide contact and/or ingestion. They also may mitigate possible repellent characteristics of the insecticide. In this study the potential of using baits or behaviour modifying chemicals to increase insecticide efficacy for Frankliniella occidentalis (Pergande) was studied in laboratory bio-assays and semi-field experiments. In bio-assays spinosad was less effective when untreated leaf area was available; efficacy could be increased by 20 to 30% by adding a sugar bait. A similar increment in efficacy was observed in a semi-field experiment when the same sugar bait was added to an experimental insecticide.