|DE Moraes, Consuelo|
Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 16, 1999
Publication Date: September 1, 1999
Citation: De Moraes, C.M., Lewis, W.J. 1999. Analyses of two parasitoids with convergent foraging strategies. Journal of Insect Behavior. 12(5):571-583. Interpretive Summary: Plant feeding insects are costly pests of agricultural crops. Resistance and residue problems with conventional pesticides have caused scientists to seek better ways to harness natural controls for insect pests. Understanding the natural enemies and how they interact with crop pests is essential to their reliable use in pest control. ARS scientists at Tifton, GA are seeking to better understand the ecology of parasitic wasps which attack the caterpillar stage of bollworms and other pests. The foraging strategies of two wasp species were examined. One species specializes only on the tobacco budworm, while the second species attacks both the tobacco budworm and corn earworm. In choice experiments with cotton and tobacco, the strongest searching response for both species was with odors of damaged plants. The specialist wasp favored the odor of tobacco, the preferred host plant of the tobacco budworm, while the more generalist wasp favored cotton. The specialist wasp demonstrated an overall keener ability to locate hosts over distances. This type information is important to choosing natural enemies for particular uses and designing effective biological control strategies.
Technical Abstract: We compared foraging strategies of two key braconid endoparasitoids of the tobacco budworm (Heliothis virescens Fab.), Cardiochiles nigriceps Vier. and Microplitis croceipes Cresson, that differ in host and habitat range but otherwise share comparable, overlapping niches. Differences in host-detection ability between the two species may account for previously observed differences n foraging efficiency. Both C. nigriceps and M. croceipes demonstrated a significant preference for volatiles released from plants damaged by H. virescens larvae over those released from undamaged tobacco and cotton plants. In choice experiments with damaged tobacco versus cotton, M. croceipes showed a significant preference for cotton plants. In contrast, C. nigriceps preferred damaged tobacco plants. The most important host-location cues by far for both species were materials associated with damaged plants. These compounds provoked a strong response even when released from systemically induced plants (from which damaged leaves, host and host by-products were removed). C. nigriceps appears to have a much keener ability to locate hosts over long distances than M. croceipes. This observation may be related to the highly specialized nature of this parasitoid. The adaptive significance of the foraging behaviors of these two parasitoids is discussed.