|Roese, Ursula - USDA, ARS, CMAVE|
|Tumlinson Iii, James|
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 2, 1997
Publication Date: N/A
Interpretive Summary: There is a great need for more effective biological control of crop plant pests with natural enemies. Scientists at the USDA, ARS, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, FL, and Insect Biology/Management Systems Research, Tifton, GA, have discovered that cotton plants that are fed upon by moth caterpillars respond by releasing odors that attract biological control agents such as parasitic wasps that attack the caterpillars. The odors are not only released from the feeding site of the caterpillars but also in large amounts throughout the entire plant. The odors that are released by the undamaged leaves of a caterpillar damaged plant are specific to herbivore feeding damage, and therefore a reliable cue for the beneficial insects. These results clearly show that the release of these herbivore specific plant odors throughout the plant increases the attractiveness of the plant to a variety of parasitic wasps. This information will be useful in developing crops that will respond rapidly and release large amounts of plant odors in response to pest damage and that will therefore attract beneficial insects faster and increase their effectiveness for biological control.
Technical Abstract: Cotton plants under herbivore attack release volatile semiochemicals that attract natural enemies of the herbivores to the damaged plant. The volatiles released in response to herbivory are not only released from the damaged leaves but from the entire cotton plant. We found that cotton plants that released myrcene, (Z)-3-hexenyl acetate, (E)-Beta- ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-Beta- farnesene, and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene systemically from undamaged leaves of caterpillar damaged plants were attractive for the generalist parasitoid Cotesia marginiventris (Cresson) and the specialist parasitoid Microplitis croceipes (Cresson). Plants that released those compounds systemically were significantly preferred over undamaged control plants in two-choice experiments in a flight tunnel. Artificially damaged cotton plants that released green leafy volatiles and constitutive terpenoids were less attractive for M. croceipes and C. marginiventris. Only C. marginiventris preferred artificially damaged plants over undamaged control plants, whereas M. croceipes showed no preference. The lack of specificity of systemically released compounds in response to different herbivores feeding on the lower leaves is discussed.