Efficacy of insecticide-infused hydrogel baits in managing European earwig (Dermaptera: Forficulidae) in citrus.

European earwig (Forficula auricularia L.) is an omnivorous insect commonly found in California citrus orchards. Often considered a beneficial predator, earwigs can damage young fruit, causing rind scarring and reducing the market value. Moreover, earwig feeding can cause defoliation of young citrus trees, thereby creating the need to manage the population. We conducted laboratory and field trials in 2024 and 2025 to evaluate the efficacy of insecticide-infused hydrogel baits for earwig management. Polyacrylamide hydrogel beads were soaked in thiamethoxam or spinosad solutions at 0.1×, 0.5×, and 1× of label rate (x). In the first laboratory trial, ∼3 cm3 of treated hydrogel prepared with 25% (w/v) added sucrose was placed in plastic containers with field-collected earwigs, with or without lemon leaves (choice and no-choice tests). The results of choice and no-choice tests showed that earwig mortality increased over time (12 to 144 h) across all concentrations and insecticides in both tests compared to the untreated check. For the field trial, ∼20 cm3 of hydrogel with added sucrose was applied per tree into the trunk wrap. The number of earwigs per tree was significantly reduced in all insecticide treatments compared to the untreated check at 6- and 14-d post-treatment. In the second laboratory trial, no significant difference in mortality was observed in bait with or without added sucrose, with mortality ranging 83.1% to 100% at 144 h. The results show that insecticide-infused hydrogel baits, regardless of added sucrose, can be a promising tool for managing earwigs in citrus orchards.