Suitability of lepidopteran stemborers for parasitization by novel-association endoparasitoids

Abstract

Extensive study of insect immune systems has yielded abetter understanding of the mechanisms used by insects to defendagainst invaders. This knowledge can be used to predict hownatural enemies utilize potential hosts, which will aid in theplanning of biological control programs. Our experimental systemconsists of novel host-parasitoid associations, with two NewWorld pyralid stalk borers, Diatraea saccharalis and D.grandiosella; one Old World crambid borer, Ostrinia nubilalis;and three Old World microgastrine braconid parasitoids, Cotesiachilonis, C. sesamiae, and C. flavipes. Experiments on hostsuitability indicate that parasitoids that are taxonomically,behaviorally and ecologically very similar may differ in theirability to utilize a host of the same species. Likewise,utilization of related hosts can produce different outcomes for agiven parasitoid species. D. saccharalis is a suitable host forall three parasitoid species, whereas D. grandiosella oftenencapsulates C. sesamiae and C. flavipes. O. nubilalis is anunsuitable host for all three species. Different species ofparasitoids may use different factors at different times afterparasitization to counter the host's immune response. This studysuggests that the physiological host range of these parasitoids willbe narrow, thus limiting effects on non-target species. However,the lack of consistent patterns also shows that explicit testingwill be needed to determine host ranges.