The European earwig Forficula auricularia (Dermaptera: Forficulidae) in California citrus: a sampling method, population surveys, and description of earwig movement into the tree canopy.

Abstract

The European earwig F. auricularia L. is an omnivore that has only recently been identified as a direct, fruit-feeding pest of citrus. Here, we start to build the basic tools needed for integrated pest management for this species. We introduce a time-efficient sampling method based on small wooden boards placed on the ground, and we use them in a 2-yr survey of 93 commercial citrus blocks in California's San Joaquin Valley. Insecticides were not applied targeting F. auricularia in any of these citrus blocks. We find that F. auricularia populations are very low or undetectable in most blocks, with higher densities occurring only sporadically. To know when control measures should be implemented, we used video-monitoring of citrus tree trunks to characterize the timing of F. auricularia movement from their soil nests into the tree canopy. Movement of earwigs along the tree trunks was observed throughout our sampling period (22 March to 18 June), suggesting that control measures (sticky bands placed on trunks, or insecticides applied to trunks and surrounding soil surface) should be applied early, well before petal fall when fruit are susceptible to F. auricularia herbivory. Sticky barriers effectively reduced the vertical movement of 2 crawling arthropods, F. auricularia and the Fuller rose beetle Napactus godmanni, along citrus trunks. We failed to find any relationship between estimated F. auricularia densities and damage to maturing or harvested fruit. This highlights a set of important and still unresolved questions about the biology of this species, underscoring the need for additional research.