Behavioral responses to host foodplants of two populations of the insect parasitoid Cotesia congregata (Say)

Abstract

To test the hypothesis that natural enemy populations differ in their behavioral responses to plants or to plant allelochemicals, we compared two populations of the gregarious larval endoparasitoid, Cotesia congregata (Say) (Hymenoptera: Braconidae) that differed in their historical and present exposure to tobacco. The major hosts for both populations were Manduca sexta L. and M. quinquemaculata (Haworth) (Lepidoptera: Sphingidae), but these hosts were typically encountered on tobacco by parasitoids in one population (Upper Marlboro) and on tomato by parasitoids in another population (Wye). Early in the season, Wye parasitoids preferred to oviposit in M. sexta on tomato rather than on tobacco and Upper Marlboro parasitoids showed no preference; neither population showed any preference later in the season. Neither of the strains originating from the two populations showed a landing preference for tobacco or tomato in flight chamber trials, but Upper Marlboro parasitoids searched longer on tobacco than on tomato, and Wye parasitoids searched longer on tomato. When nicotine solutions were applied to tobacco leaf, searching responses of Upper Marlboro parasitoids were enhanced by 0.001-1.0% nicotine, and searching responses of Wye parasitoids were decreased by 0.01-1.0% nicotine. We speculate that population differences in searching responses to tobacco and nicotine may explain the differential parasitism responses found early in the season.

Incidence of Parasitoids and Parasitism ofBemisia tabaci(Homoptera: Aleyrodidae) in Numerous Crops

“…They noted that previous researchers testing Encarsia formosa Gahn in olfactometers, did not observe any plant odor or host recognition. Many other parasitoid species have been shown to orient toward plant volatiles (e.g., Martin et al 1990, Whitman and Eller 1990, Kester and Barbosa 1994, Whitman and Nordlund 1994, Geervliet et al 1996. Leaves which are insect or mechanically damaged are more likely to elicit a response from some parasitoids compared with undamaged leaves, such as used in our greenhouse experiment.…”

The roles of nicotine and natural enemies in determining larval feeding site distributions of Manduca sexta L. and Manduca quinquemaculata (Haworth) on tobacco

“…Alternatively, feeding on low-nicotine regions of tobacco leaves may constitute a counteradaptation for evasion of parasitism by tobaccoadapted C. congregata. For example, females of C. congregata from this same ''tobacco population'' show a positive dosage-dependent searching response to nicotine that differs from that of females collected from a ''tomato population'' and these differential responses can be linked to parasitism levels of M. sexta on tobacco and tomato in the field (Kester & Barbosa 1991, 1994. Predation risk alone did not differ significantly among within-leaf feeding site locations (P \ 0.05, N= 73; Table 2B, Fig.…”

“…Tobacco plants were started from seed in a greenhouse and then transplanted to the experimental research farm of the University of Maryland, Upper Marlboro (Prince George's County), Maryland in 1986 and 1987, as described in Kester & Barbosa (1994). Plants used in field experiments were chosen for their healthy and uniform appearance; experimental treatments within each patch were randomly assigned.…”

Variability and genetic components of innate fruit odour recognition in a parasitoid of Drosophila

“…Genetic variability was also documented on different behavioural traits in studies of evolutionary mechanisms and of the use of parasitoids in biological control (e.g. host or host plant selection behaviours: Kester & Barbosa, 1994;Potting et al, 1997;locomotion activity: Bigler et al, 1988;Fleury et al, 1995;host and patch exploitation: Wajnberg, 1994). However, so far the genetic component of the variability was weak when investigated in responses to olfactory cues (Potting et al, 1997;Pe rez-Maluf et al, 1998;Gu & Dorn, 2000).…”