Effects of pepper (Capsicum chinense) genotypic diversity on insect herbivores

There is growing interest on the effects of plant genotypic diversity on higher trophic levels. The present study investigated whether genotypic diversity in Capsicum chinense peppers influenced attack by leaf-mining fly larvae (Lyriomyza trifolii) and fruit-eating weevils (Anthonomus eugenii), as well as parasitoid attack associated with weevils. We established genotypic monocultures (n=10, two plots/each of five inbred lines) and polycultures (n=5, random mixtures of three out of the five lines) and conducted weekly surveys of fruit number, leafmines and weevil fruit attack over a 5-month period. In addition, we collected fruits to rear weevils and estimated parasitism associated with this herbivore. There was a tendency for a negative effect of diversity on leafminer attack, with polycultures exhibiting a 24% reduction in leafminer attack relative to monocultures. By contrast, diversity did not influence weevil fruit attack or the level of parasitism associated with the weevil. Our findings show that plant genotypic diversity effects vary among herbivore species, presumably as a result of differences in herbivore traits (e.g. diet breadth, mobility). We also emphasize that manipulating plant genotypic diversity can be an important consideration for pest management in this commercially important crop.