Forficula auricularia (Dermaptera) in orchards: Monitoring seasonal activity, the effect of pesticides, and the perception of European fruit growers on its role as a predator or pest

Abstract

Background: We investigated several aspects that could affect the role of the European earwig (Forficula auricularia) as a generalist predator in orchards: (i) seasonal activity in apple orchards, (ii) effectiveness of two cardboard trap types (roll vs tape) to enhance earwig densities, (iii) the effect of pesticides (chlorpyrifos-methyl, spinosad, indoxacarb, spirotetramat, pirimicarb, sulphur, fluopyram tebuconazole) on earwig survival and behaviour, and (iv) the perception of European fruit growers of the earwigs' role as a predator or pest.

Results: The highest activity of earwigs in apple trees was observed in summer. Roll traps were a more effective capture method than tape traps. The roll traps also significantly increased earwig abundances in trees. Only the earwigs exposed to the insecticides indoxacarb, spinosad and chlorpyrifos-methyl had significantly higher mortality and more erratic behaviour than earwigs from the control treatment. Earwigs from orchards with long-term (>10 years) application of chlorpyrifos-methyl had significantly lower mortality when exposed to this insecticide than earwigs from nonsprayed orchards. The fruit growers perceived earwigs as natural enemies of aphids and psyllids but also as pests. However, they regarded the damage caused by earwigs as economically unimportant without the necessity for management against them.

Conclusion: Fruit growers can increase earwig densities by installing rolled cardboard bands around trees. The highest seasonal activity of European earwigs coincides with applications of insecticides in orchards. This could disturb the earwigs' potential to suppress pest populations because several insecticides widely used in orchards have lethal and sublethal effects on earwigs even though they seem to develop some degree of pesticide resistance over time. © 2020 Society of Chemical Industry.

Keywords: biological control; earwig; fungicide; insecticide; integrated pest management; organic management; pest.