Comparing different test methods for evaluating lethal side effects of some insecticideson the European earwig Forficula auricularia L.

Abstract: In top fruit, the European earwig Forficula auricularia L. (Dermaptera: Forficulidae)can contribute to the biological control of several pests e.g. woolly apple aphid (Eriosomalanigerum Hausmann) and pear sucker (Psylla pyri L.). Studies on population dynamics revealedthe vulnerability of earwigs to pesticides due to their univoltine life cycle. Foliar applications ofplant protection products during spring and/or summer cannot only have an impact on the presentgeneration but also on the next one. In lab trials with different methodology (residual contactbioassays on inert and natural substrate, direct contact assay and ingestion of treated food) theinfluence of indoxacarb, methoxyfenozide and deltamethrin on adult earwigs was evaluated. Asexpected lethal effects were the highest when tested on an inert substrate. Maximum mortalitycaused by dried residue of deltamethrin and indoxacarb was 90.0% and 100.0% respectively. Theresidual effect of all compounds was lowered and less than 30% when they were sprayed on anatural substrate. Direct spraying of deltamethrin on earwigs was more harmful than indoxacarb(100.0% vs. 66.7%) whereas methoxyfenozide was harmless. Uptake of food sprayed withdeltamethrin induced 75.0% mortality, indoxacarb and methoxyfenozide less than 30%.