Abstract

Euborellia annulipes (Dermaptera: Anisolabididae) is a cosmopolitan earwig with a dual role in agroecosystems, acting both as a predator of agricultural pests and as a secondary pest feeding on tender plant tissues. This biological and behavioral duality, together with maternal care and high environmental tolerance, makes E. annulipes a relevant model for evaluating stage-dependent susceptibility and host-pathogen interactions in biological control systems. We assessed the susceptibility of different developmental stages to native isolates of entomopathogenic nematodes (EPNs) from the genera Steinernema and Heterorhabditis and evaluated the effect of diatomaceous earth (DE) as a physical adjuvant to enhance infection outcomes. Among ten EPN isolates, Steinernema unicornium (UOH-006), S. australe (UOH-030), and S. feltiae (UOH-A7) caused the highest mortality in nymphs and adults (>30%), with nymphs exhibiting greater susceptibility and lower LD50 values than adults. Maternal care markedly reduced EPN-induced mortality in eggs and first-instar nymphs. In the absence of maternal care, late-stage egg mortality reached 73.6 +/- 3.0%, whereas under maternal protection mortality rarely exceeded 15%. Isolate UOH-006 showed the highest pathogenic potential, causing the greatest mortality in nymphs and eggs without maternal care, and was the only isolate capable of infecting eggs under maternal care, reaching 15.3 +/- 5.8%. The combined application of DE and EPNs significantly increased mortality in nymphs and adults, in some cases doubling the efficacy of EPNs alone, but did not enhance egg mortality, indicating that chorion structure and maternal behavior constrain pathogen entry. Overall, these findings show that E. annulipes is differentially susceptible to selected EPNs, that DE enhances infection and control efficacy in mobile stages, and that maternal care represents a key barrier shaping biological control outcomes in earwigs with protective behavior.