Application of Multitrophic Interactions Knowledge

Information about multitrophic-level interactions can provide an essential foundation for designing effective biological control (#57 Lewis et al., 1997). Too often we have failed to appreciate the complexity of variables within the habitat, crop and the biological agent that must be managed in order to foster effective biological control. It is clear that the conditions within the habitat arena as well as with the biological agent must match properly for effective biological control. The host plant and habitat must provide the appropriate host, adult food, and other resources along with vital foraging cues, while the parasitoids or other natural enemies must be in the proper condition in regard to genetic, informational state, and physiological state for that arena.

 

The parasitoid Microplitis croceipes starts spinning a cocoon as soon
as it emerges from its host Helicoverpa zea. The host will eventually die.


In the case of conservation biological control, which should be of first priority where possible, we must design and promote good habitat management/landscape ecology practices that provide adequate year-round refugia, hosts, food, and foraging conditions for the natural enemy abundance and balance with the pests. Also, we must choose crop varieties with appropriate attributes for interacting with parasitoids or other natural enemies, and we must manage the plants so as to insure appropriate expression of these natural enemy friendly attributes. As documented in this webpage these attributes include provision of nectar or other adult food needs and emission of foraging cues in response to herbivore damage. Further, we must use supplemental inputs such as fertilizers, pesticides, and tillage in ways that compliment and not disrupt this inherent system. Thus, an ecologically based approach as depicted in the figure below must be employed.

 


Also, more complete information about parasitoids as a component of the total system can be used to guide and enhance the explorations, importation and effective establishment of new natural enemies into a cropping system. Formulations of selected cues, hosts and/or food resources can be applied to the crop to lure the parasitoid and retain them in an effective behavioral state. Traps, using the cues as baits, can be developed for monitoring the presence and density of parasitoids. Behavioral and physiological state qualities of laboratory-produced parasitoids can be improved, in the case of augmentative releases, through the use of cues for pre-release conditioning.
See the table below for an outline of these potential approaches. Development of truly ecologically based pest management and other sustainable agricultural practices will necessitate that we better understand and foster natural enemies as a component of the agroecosystem.


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