Development of a bioassay method for evaluating slow-acting insecticides against Frankliniella intonsa (Trybom)

Abstract

To evaluate the efficacy of slow-acting insecticides against Frankliniella intonsa, Frankliniella occidentalis, Thrips palmi, and Thrips tabaci, a bioassay method was developed and tested. We validated this bioassay method (dip test) using kidney bean (Phaseolus vulgaris L.) leaf discs placed on water-moistened cotton pads to maintain their freshness. Then we assessed the efficacy at two and seven days after treatment. The results demonstrated high applicability to only Frankliniella intonsa: control mortality was less than 10% after seven days. Emamectin benzoate and cyantraniliprole exhibited low efficacy two days after treatment, but both compounds showed high efficacy seven days after treatment, which indicated delayed action of these insecticides.

In contrast, this method was not appropriate for the other three species due to high control mortality (>20%) seven days after treatment.

These findings suggest that the method contributes to selection of effective insecticides, particularly for Frankliniella intonsa controls.