CONTROL OF WESTERN FLOWER THRIPS (FRANKLINIELLA-OCCIDENTALIS PERGANDE) PUPAE IN COMPOST

Western flower thrips (Frankliniella occidentalis) develops from an ac tive larval stage through to a non-feeding, almost immobile, pre-pupal and pupal stage. This generally occurs in the compost or soil below t he plant on which the larvae fed. Control of thrips at this stage in t heir development offers a chance of utilising pathogens or pesticides not suitable for use in an integrated control programme aimed at adult and larval stages. Trials were done with F. occidentalis pupae and pr e-pupae in a soil/peat based compost using 11 pesticides, three fungal pathogens and four species of insect parasitic nematodes. The pestici des malathion and chlorpyrifos-methyl gave the most promising result w ith 97.5% and 96.5% control, respectively. The fungal pathogen Metarhi zium anisopliae proved better when applied as a pre-pupation rather th an as a post-pupation treatment (74.5% : 26.6% control). The insect pa rasitic nematode Steinernema carpocapsae gave 76.6% control when appli ed at 25 x 10(4) nematodes litre(-1) of compost. The results are discu ssed in relation to control of thrips in glasshouses.