Kikikose jeudi 19/10
John Tooker, Penn State University
Unforeseen trophic interactions in agricultural and natural systems influence herbivore populations
12h45 amphi P
Top-down and bottom-up effects are well known regulators of herbivore populations. Our recent research has revealed some unexpected strengths of both types of effects, one in field crops and the other with the goldenrod Solidago altissima, that have made us better appreciate the subtleties of these interactions. In no-till corn and soybean fields in Mid-Atlantic States of the U.S., slugs are challenging pests for farmers, but carabid beetles can help provide biological control. Unfortunately, our recent research has found that ubiquitous neonicotinoid seed treatments can disrupt this predator-mediated control. Our follow-up work has revealed the extent of adoption neonicotinoid seed treatments and the generality of their effects on natural enemies. In the goldenrod system, we have found that S. altissima can detect and respond to the volatile emission of its co-evolved gall-inducing herbivore; more recently we have determined that this response can be triggered by only the dominant compound in the emission. This perception of an animal-derived cue and up-regulation of plant defenses has unexpectedly strong community-wide effects that help structure the insect community on plants exposed to the odor.