Submitted to: BARC Poster Day
Publication Type: Proceedings
Publication Acceptance Date: February 18, 2000
Publication Date: N/A
Interpretive Summary: The melon fruit fly, B. Cucurbitae, is becoming a more serious pest in many parts of the world, including Hawaii, but to date has not become established in the continental U.S. Cue-lure, discovered in 1959 by Beroza et al., is still the most commonly employed attractant for melon flies and other Bactrocera spp. in spite of efforts to develop superior lures. Cue-lure satisfies the state of California's requirements for melon fly monitoring, but has limitations, for example, it is not sufficiently attractive to achieve eradication of melon fly populations by the male annihilation method, possibly because of limited volatility. We have synthesized and tested 16 compounds incorporating important structural features of raspberry ketone while attempting to maximize volatility, as potential melon fly attractants. One compound showed higher attractancy than raspberry ketone in the field, and was equivalent in activity to Cue-lure. In addition, bubbling air or carbon dioxide through solutions of raspberry ketone, adding cosolvents, or increasing the temperature all increase the rate of volatilization of raspberry ketone. Improved lures and dispensing technology will be used by the state of California in its monitoring programs, and by growers in Hawaii to assess local melon fly populations.
Technical Abstract: Cue-lure, discovered in 1959 by Beroza et al., is still the most commonly employed attractant for melon flies and other Bactrocera spp. in spite of efforts to develop superior lures. It is used in the detection, delimitation, and suppression of populations of melon fly and other fruit fly species of economic and quarantine significance (e.g. Bactrocera tryoni iand Bactrocera tau). However, cue-lure has limitations, e.g., it is not sufficiently attractive to achieve eradication of melon fly populations by the male annihilation method. Cue-lure is the acetate of raspberry ketone, another effective attractant for Bactrocera spp. Structure-activity relationship studies in B. cucurbitae with various analogs of raspberry ketone showed that highest activity was associated with raspberry ketone itself. It has been suggested that hydrolysis of cue-lure by atmospheric moisture releases raspberry ketone which acts as the actual attractant. We have synthesized and tested 16 analogs of raspberry ketone as potential melon fly attractants, and we tested them in outdoor olfactometer cages and later in the field. In the field, one silylated compound showed statistically significant higher attractancy than raspberry ketone, and no statistical difference than cue-lure. A few additional compounds will be synthesized. In addition, we have examined the effect of bubbling air or C02 through solutions of raspberry ketone under different conditions, for improvement of the lure in the field. Raising the temperature is one of the most important factors in the rate of raspberry ketone volatization, but the presence of water or organic solvents (ethanol, acetone) can enhance evaporation rates. The degree of enhancement seems to parallel the volatility of the solvent (acetone>ethanol>water).