Antennal Responses of West Indian and Caribbean Fruit Flies (Diptera: Tephritidae) to Ammonium Bicarbonate and Putrescine Lures

Efforts to monitor and detect tephritid fruit flies in the genus Anastrepha currently involve MultiLure traps baited with two food-based synthetic attractants, ammonia (typically formulated as ammonium acetate or ammonium bicarbonate) and putrescine (1,4-diaminobutane). These baits are used in Central America, Florida, Texas, and the Caribbean to target/capture economically important Anastrepha spp. within each region. The efficacy of these baits varies by region and by species. Antennal responses to these compounds have been quantified for A. suspensa populations in Florida, but not elsewhere. This is the first report of antennal responses of Puerto Rican populations of A. obliqua and A. suspensa to the bait odors emitted from ammonium bicarbonate and putrescine lures. Responses to lure volatiles (tested separately and in combination), as measured by electroantennography (EAG), were dose dependant for both species and both sexes. Although the average response to ammonium bicarbonate in combination with putrescine was always numerically higher than responses to ammonium bicarbonate alone within a species and a sex, this result was never statistically significant. Males of A. obliqua were less sensitive than females, while males of A. suspensa were more sensitive than females to all volatiles and volatile mixtures, but these differences were not statistically significant at any dose. Female A. obliqua were more sensitive than A. suspensa females at all doses for all volatiles and all volatile mixtures, and these differences were statistically significant at the two highest doses of ammonium bicarbonate and ammonium bicarbonate plus putrescine. Our results are broadly similar with the electrophysiological studies conducted on Florida populations of A. suspensa, but there are important differences, most notably that the Florida study detected significantly lower responses by males than females to putrescine and ammonium bicarbonate plus putrescine. The implications of our results are discussed with respect to monitoring practices in different regions.