such issues as arthropod signaling, antagonism/toxicity/ antibiosis, host selection, target-host diseases, target-host parasitism, and plant-disease resistance are subjects in need of understanding at behavioral, molecular, and physiological levels.

Manipulating the Behavior of Pests to Reduce the Risk of Pest Outbreaks

Modifying pest behavior to reduce pest damage is a more long-lasting approach to pest management than pest destruction; however, success with behavior modification of pests and natural control agents has been restricted to a limited number of cases. There have, however, been some advances made in molecular biology and behavioral studies that have highlighted the need for researchers to cooperate on signaling system projects. Tumlinson and his colleagues formed an interdisciplinary team to investigate plant, herbivore, and parasitoid interactions (Tumlinson et al., 1993). They found that oral secretions of herbivores activate plants to emit a set of volatile signals that benefit both the plant and parasitoids by alerting the parasitoids to the presence and location of their herbivore hosts. They further report that these biological-control organisms learn to process visual and olfactory information to more efficiently locate plant pests.

Although "behavior" is generally considered to be a property of multicellular organisms, microbes also respond to signals that control behaviors such as mating, "feeding," movement, and germination; so behavior-based management techniques could also be developed for some microbes.

Knowledge that some arthropod and nematode pests must locate and recognize a crop as a food source can guide scientists to chemicals capable of controlling pest foraging behaviors. An understanding of organisms' behavior in managed ecosystems can also help scientists design cropping systems that favor the success of biological-control organisms and reduce pest damage (Kareiva, 1990; Lewis et al., 1990). For example, arthropod pests can be lured away from a valuable crop by planting a less vulnerable or less valuable trap crop nearby. Knowledge gained from manipulating the behavior of arthropod pests could be useful in research to manage weeds and pathogens.

Signaling between Target Hosts and Biological-Control Organisms

There is much interest in identifying signals and elucidating the nature of signal reception and transduction in organisms. Chemical signals influence an organism's growth and development and affect interactions between different organisms, such as in the induction of host-defense responses. Much is known about the role of signal molecules and physical cues in determining the behavior of arthropods; but more comprehensive knowledge of the nature and function of these signals is needed if they are to be exploited for biological control of pests,



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