Herbivory by European Earwigs (Forficula auricularia; Dermaptera: Forficulidae) on CitrusSpecies Commonly Cultivated in California

Agricultural plant species differ in susceptibility to herbivores; therefore, identifying natural resistances or tolerances to pests can be leveraged to develop preventative, integrated pest management approaches. While many Citrusspecies are grown in California, most pest management guidelines are based upon research conducted on navel oranges [Citrus sinensis(L.) Osbeck; Sapindales: Rutaceae]. A recent study has established European earwigs (Forficula auriculariaL.; Dermaptera: Forficulidae) as herbivores of young navel orange fruit, causing damage ranging from small bite marks to large chewed holes. It is unknown whether earwigs damage fruit of other citrus species. We conducted field experiments in which we caged earwigs to branch terminals bearing young fruit to explore potential differences in susceptibility of Citrusspecies to European earwigs. Specifically, we tested whether three species, navel oranges, clementines (C. clementinahort. ex Tanaka), and true mandarins (C. reticulataBlanco) exhibit differences in: 1) feeding deterrence to earwigs; 2) suitability as food for earwigs; 3) preferential abscission of damaged fruit; and 4) healing of damaged fruit. Earwigs caused heavy damage on navel orange and clementine fruit, whereas heavy damage was rare on true mandarin fruit. There was little evidence of preferential abscission of damaged fruit or healing of seriously damaged fruit. Consequently, several heavily damaged navel orange and one clementine fruit were retained to harvest and developed large scars. Overall, we found that Citrusfruit vary in their susceptibility to earwigs, and pest management strategies for earwigs should be refined to consider their varying effects on different Citrusspecies.