Control of Western flower thrips <i>(Frankliniella occidentalis</i> Pergande) pupae in compost

Abstract

Summary Western flower thrips (Frankliniella occidentalis) develops from an active larval stage through to a non‐feeding, almost immobile, pre‐pupal and pupal stage. This generally occurs in the compost or soil below the plant on which the larvae fed. Control of thrips at this stage in their 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 pre‐pupae in a soil/peat based compost using 11 pesticides, three fungal pathogens and four species of insect parasitic nematodes. The pesticides malathion and chlorpyrifos‐methyl gave the most promising result with 97.5% and 96.5% control, respectively. The fungal pathogen Metarhizium anisopliae proved better when applied as a pre‐pupation rather than as a post‐pupation treatment (74.5% : 26.6% control). The insect parasitic nematode Steinernema carpocapsae gave 76.6% control when applied at 25 times 10 4 nematodes litre ‐1 of compost. The results are discussed in relation to control of thrips in glasshouses.