Underground influences: Cover crop legacies modulate corn defense hormones and herbivore success

While cover cropping is recognized for its soil health benefits, its influence on plant defense chemistry and herbivore performance via plant-soil feedbacks remains poorly understood. Previous research shows that cover crops leave behind unique microbial and chemical legacies based on plant family and physical characteristics; we hypothesize that these legacies will differentially influence corn’s defense profiles and aphid performance. For example, pea-conditioned soils may enhance salicylic acid (SA) signaling and suppress aphid growth. In this experiment, we examined how winter-grown cover crops affect corn defense responses and the performance of the corn leaf aphid (Rhopalosiphum maidis) in the subsequent summer. Three cover crops—pea (Pisum sativum), radish (Raphanus sativus), and triticale (× Triticosecale)—were grown over winter and incorporated into soil in spring. Corn was then planted into these legacy soils and compared to a fallow control. Plants were inoculated with aphids, and we assessed aphid population growth over a three-week period. Additionally, we quantified constitutive and induced levels of defense-related phytohormones in maize leaf tissue—specifically, salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA), which mediate responses to phloem-feeding insects. This study links soil legacy effects to pest dynamics and highlights how cover crop selection can shape aboveground herbivore interactions. Our findings provide insight into designing sustainable integrated pest management strategies rooted in chemical ecology.