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Title: COMPARISONS AND CONTRASTS IN HOST FORAGING STRATEGIES OF TWO LARVAL PARASITOIDS WITH DIFFERENT DEGREES OF HOST SPECIFICITY

Author
item CORTESERO, A. - UNIVERSITY OF GA, ENTOMO.
item DE MORAES, C. - UNIVERSITY OF GA, ENTOMO.
item STAPEL, J. - UNIVERSITY OF GA, ENTOMO.
item Tumlinson Iii, James
item Lewis, Wallace

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plant feeding insects are costly pests of agricultural crops. Resistance to chemical pesticides and residue problems have caused scientists to seek better ways to use natural enemies for the control of insect pests. Understanding natural enemies and how they interact with crops and crop pests is essential to their dependable use in pest control. ARS scientists at Tifton, GA are seeking to better understand the host searching behavior of parasitic wasps which attack the caterpillar stages of earworm, bollworm, and armyworm. Odors produced by plants in response to caterpillar feeding help wasps identify plants that are infested with larvae. Flight chamber studies showed that these plant signals play a crucial role in the early detection of insect pests for both generalist and specialist wasps. This information can be used to maximize the effectiveness of beneficial wasps as biological control agents.

Technical Abstract: In theory, the degree of specificity of the signals a parasitoid species needs to successfully locate its hosts correlates with its level of specialization. We analyzed this question by comparing the foraging strategies of two parasitoids that differ in their host ranges. In wind tunnel experiments, we investigated how systemically released herbivore-induced volatiles were used by the generalist parasitoid, Cotesia marginiventris and the specialist, Microplitis croceipes. We determined the relative influence of these systemically released plant volatiles as compared to other signals emitted in the long and short range orientation of the two parasitoids. Both, the generalist and the specialist parasitoid strongly preferred leaf-induced systemic plant volatiles over undamaged plant volatiles when no other information was available. When plants were damaged at the squares, only M. croceipes exhibited a preference for these plants over undamaged plants. The information used in close range host location differed between the two species; C. marginiventris appeared to cue primarily on volatiles from recent damage, whereas, M. croceipes appeared to cue primarily on volatiles from host frass.