Selective leaf surface defenses: trichomes trap herbivorous leafminers but spare parasitoid wasps

Abstract

BACKGROUND: Leafminers [e.g., Liriomyza trifolii (Burgess), L. sativae (Blanchard), and Chromatomyia horticola (Goureau)] are globally significant agricultural pests, while their parasitoid wasps [e.g., Hemiptarsenus varicornis (Girault) and Neochrysocharis formosa (Westhood)] are key agents in biological control programs. Although trichomes are known to act as physical defenses against herbivores, their potential for selective entrapment—targeting pests while sparing natural enemies—has remained underexplored. This study aimed to evaluate whether kidney bean (Phaseolus vulgaris L.) leaf trichomes exert species-specific physical effects on leafminers and their parasitoids. RESULTS: Laboratory assays showed that 30–40% of adult leafminers became entangled and died on the abaxial surface of primary leaves. In contrast, only 1.6–3.3% of parasitoid wasps were similarly affected. Scanning electron microscopy revealed that hook-shaped non-glandular trichomes effectively trapped leafminer legs, ovipositors, and mouthparts, regardless of sex or age. In contrast, parasitoids avoided entrapment, consistent with their markedly thinner legs and smaller body size. Removal of trichomes drastically reduced leafminer attachment but did not reduce and increase parasitoid parasitism efficiency. CONCLUSION: Kidney bean plants exhibit a selective physical trapping mechanism that disproportionately affects herbivorous pests while sparing their parasitoid natural enemies. This species-specific interaction, governed by trichome morphology and insect body structure, provides an example of a plant defense trait that is compatible with biological control. These findings highlight the potential for leveraging natural plant defenses to enhance the selectivity and ecological compatibility of integrated pest management programs. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.