Cover crop selection alters plant chemical defenses and predator behavior

Penn State researchers studied how different cover crops affect plant defenses against pests. They found that pea cover crops increased indole emissions and made caterpillars more attractive to predatory insects, but reduced levels of the natural toxin benzoxazinoid. This trade-off suggests growers can choose cover crops to influence pest resistance.

The study, published in Basic and Applied Ecology, tested corn grown in soil conditioned by pea, radish, or triticale cover crops, with fallow soil as a control. Fall armyworm larvae were raised on these plants while researchers measured defensive chemistry and volatile emissions. Pea-conditioned soil boosted indole output—a compound that signals neighboring plants to ramp up stress hormones—yet simultaneously suppressed benzoxazinoid, a natural toxin with pesticide-like properties.

Lead researcher Jared Ali frames the work within plant domestication, noting that selective breeding for yield and taste inadvertently stripped crops of protective traits, much like domestication tamed wolves into dogs. The findings suggest growers might leverage cover crop choice to restore some of those lost defenses without abandoning familiar agricultural practices.