Ecology in the service of biological control: the case of entomopathogenic nematodes |
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Authors: | R Gaugler Edwin Lewis Robin J Stuart |
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Institution: | (1) Department of Entomology, Rutgers University, New Brunswick, NJ 08903–0321, USA, US;(2) Department of Entomology, University of Maryland, College Park, MD 20742, USA, US |
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Abstract: | Biological control manipulations of natural enemies to reduce pest populations represent large-scale ecological experiments
that have both benefited from and contributed to various areas of modern ecology. Unfortunately, economic expediency and the
need for rapid implementation often require that biological control programs be based more on trial and error than on sound
ecological theory and testing. This approach has led to some remarkable successes but it has also produced dismal failures.
This point is particularly well illustrated in the historical development and use of entomopathogenic nematodes for the biological
control of insect pests. Intense effort has focused on developing these natural enemies as alternatives to chemical insecticides,
in part because laboratory assays indicated that these nematodes possess a broad host range. This illusory attribute launched
hundreds of field releases, many of which failed due to ecological barriers to infection that are not apparent from laboratory
exposures, where conditions are optimal and host-parasite contact assured. For example, the entomopathogenic nematode Steinernema carpocapsae is a poor choice to control scarab larvae because this nematode uses an ambusher foraging strategy near the soil surface whereas
the equally sedentary scarab remains within the soil profile, shows a weak host recognition response to scarabs, has difficulty
overcoming the scarab immune response, and has low reproduction in this host. Conversely, two other nematodes, Heterorhabditis bacteriophora and S. glaseri, are highly adapted to parasitize scarabs: they use a cruising foraging strategy, respond strongly to scarabs, easily overcome
the immune response, and reproduce well in these hosts. Increased understanding of the ecology of entomopathogenic nematodes
has enabled better matches between parasites and hosts, and more accurate predictions of field performance. These results
underline the importance of a strong partnership between basic and applied ecology in the area of biological control.
Received: 15 July 1996 / Accepted: 5 November 1996 |
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Keywords: | Nematode Biological control Host habitat-finding Host-finding Host acceptance |
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