Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2011
Publication Date: 5/16/2011
Citation: Niogret, J., Montgomery, W.S., Kendra, P.E., Heath, R.R., Epsky, N.D. 2011. Attraction and electroantennogram responses of male Mediterranean fruit fly (Diptera: Tephritidae) to volatile chemicals from Persea, Litchi and Ficus wood. Journal of Chemical Ecology. 37:483-491. Interpretive Summary: The Mediterranean fruit fly is the most important pest of fruits and vegetables worldwide. a-copaene, a chemical found in both host and non-host plants, has been suspected to be a natural attractant for males of this pest insect. Therefore, scientists at the Subtropical Horticulture Research Station tested response of males to natural sources of a-copaene, including avocado, weeping fig and lychee wood; and determined the chemical profiles of these materials. Males responded to all tested sources and showed preferences among the different woods. Response was not correlated with the quantity of a-copaene but was correlated with other identified chemicals. Results from this study will be used to identify additional chemicals that may provide more effective control techniques for this destructive pest and also information on the biological significance of these natural compounds. The results of this research will be used by regulatory agencies and growers, will provide a significant improvement in our ability to detect Mediterranean fruit fly populations and may afford a critical component in the areawide control of this pest.
Technical Abstract: Trimedlure is the most effective male-targeted lure for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). A similar response is elicited by plant substances that contain a-copaene, a naturally-occurring sesquiterpene. a-copaene is a complex, highly-volatile, widely-distributed plant compound, and male C. capitata respond to material from both hosts (e.g., Litchi chinensis) and non-hosts (e.g., Ficus benjamina) that contain a-copaene. Avocado, Persea americana, was recently found to contain varying amounts of a-copaene in the bark and underlying cambial tissue. Short-range attraction bioassays and electroantennography (EAG) were used to quantify responses of sterile male C. capitata to samples of rasped wood from four avocado genotypes, L. chinensis and F. benjamina. GC-MS analysis was used to identify and quantify the major sesquiterpenes. Attraction and EAG amplitude were correlated, with L. chinensis eliciting the highest and F. benjamina the lowest responses. Responses to the avocado genotypes were intermediate, but varied among the four types. GC-MS identified 13 sesquiterpenes, including a-copaene, from all samples. Amount of a-copaene in volatile collections from samples (3 mg) ranged from 11.8 µg in L. chinensis to 0.10 µg in F. benjamina, which correlated with short-range attraction and EAG response. a-copaene ranged from 8.0 to 0.8 µg in the avocado genotypes, but attraction and EAG responses were not correlated with the amount of a-copaene. Differences in enantiomeric structure of the a-copaene in the different genotypes and/or presence of additional sesquiterpenes may be responsible for the variation in male response. EAG responses were correlated with the amount of several other sesquiterpenes including a-humulene, and this compound elicited a strong antennal response when tested alone. Additional studies are needed to assess a-humulene as a potential semiochemical for male C. capitata.