Microspace refuges on strawberry plant reduce the effect of pesticides on predatory thrips, Haplothrips brevitubus (Karny)

Abstract

Predatory thrips, Haplothrips brevitubus (Karny), is an effective natural enemy for the control of pest thrips infesting strawberries in the greenhouse. To develop an IPM program using H. brevitubus, it is required to select pesticides which can be used with this predator based on the data from side-effect experiments conducted in the laboratory. In this study, we investigated the effects of three insecticides on H. brevitubus using strawberry plants in greenhouses. Although spraying these insecticides results in a high mortality of this species in laboratory experiments, we found that there were substantial individuals of this species on the plants after treatments of spinosad, spinetoram, or emamectin benzoate. Individuals of H. brevitubus, especially larvae who survived after spraying the pesticides, were seen in microspace refuges on strawberry flowers and young fruits. We consider that such microspace refuges on the strawberry plant might reduce the effect of the pesticide on H. brevitubus.