Population dynamics and functional response of the European earwig (Dermaptera: Forficulidae) to biotic factors, environmental resistance, and peach-orchard management

European earwigs, Forficula auricularia L., are omnivorous insects that can densely populate peach orchards, Prunus persica L., of northern Utah, USA. Their functional ecology and economic impact are dynamic and presumably determined by various biotic, environmental, and agricultural-management factors. We monitored and modeled earwig population dynamics (such as abundance, dispersal, frugivory, age-stage structure, reproduction, etc.) to a variety of factors that were hypothesized to affect community dynamics in ways that might be utilized by orchardists. Experiments were conducted between 2010 and 2013 within two, half-hectare peach orchards in Kaysville, Utah. Planted in 2006, the orchards were subjected to management treatments, applied in a completely randomized, block design. The treatments represented industry standard (tillage, herbicide, grass alleyways) and experimental production systems (such as mulches, cover crops, and leguminous alleyways). Earwigs were monitored weekly in refuge traps and twice with mark-recapture experiments. Weeds and other arthropods were monitored monthly. Earwig abundance increased yearly and seasonally until the carrying capacity was reached. Earwigs, vegetation, prey arthropods, and fruit damage varied by treatment and important ecological correlations were detected. Pests were negatively affected by earwig density, likely due to earwig predation. Leguminous treatments harbored the greatest number of earwigs, presumably due to high refuge and nitrogen availability. Abundance was the lowest, and emigration was greatest, in tillage treatments, suggesting that it was the superior treatment for reducing earwigs. Straw mulch harbored relatively high earwig densities, yet had the lowest damage at harvest, suggesting that it could be an ideal method for endorsing conservation biocontrol.