Discrimination of Chemical Stimuli of Immature Papaya Fruit Oviposited and Not Oviposited in by Female Toxotrypana curvicauda ¹

Attraction response of female Toxotrypana curvicauda (Gerstaecker) to volatile compounds from immature fruit of papaya (Carica papaya L.) and of gravid females to papaya fruit oviposited and not oviposited in was studied with the aid of an olfactometer. Response of virgin and mated females (4-6 days old) to immature papaya fruit covered or not with Lycra netting was evaluated. After greatest attraction response had been recorded, extracts were obtained by dynamic aeration. The compounds were identified by gas chromatography-mass spectrometry. Attraction response of females to papaya extracts obtained using three solvents was studied by bioassays in a wind tunnel. From the extracts were identified eight compounds: An aldehyde, two heterocompounds, four hydrocarbons, and a terpene. Hexanic extract resulted in most landing by virgin females on an odor source (10%); however, no statistically significant differences were observed among treatments. A synthetic blend was created, based on the hexanic extract compounds, and its attraction was evaluated. Virgin females were more attracted; however, only 5% landed on the odor source. Mostly only mated females were attracted to hexanic extract (15% of long flights and 5% landings). Nevertheless, as demonstrated in electroantennography responses, virgin and mated females were attracted to the synthetic blend, with the largest polarization values. Mated females were more attracted to fruit not oviposited than oviposited in, implying they evade intra-specific competition.