Previous studies suggest that olfactory cues from damaged and fermented fruits play important roles in resource recognition of polyphagous spotted wing Drosophila flies (SWD), Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). They are attracted to fermented sweet materials, such as decomposing fruits but also wines and vinegars, and to ubiquitous fermentation volatiles, such as acetic acid and ethanol. Gas chromatography coupled with electroantennographic detection (GC-EAD), gas chromatography-mass spectrometry (GC-MS), two-choice laboratory bioassays, and field trapping experiments were used to identify volatile compounds from wine and vinegar that are involved in SWD attraction. In addition to acetic acid and ethanol, consistent EAD responses were obtained for 13 volatile wine compounds and seven volatile vinegar compounds, with all of the vinegar EAD-active compounds also present in wine. In a field trapping experiment, the 9-component vinegar blend and 15-component wine blend were similarly attractive when compared to an acetic acid plus ethanol mixture, but were not as attractive as the wine plus vinegar mixture. In two-choice laboratory bioassays, 7 EAD-active compounds (ethyl acetate, ethyl butyrate, ethyl lactate, 1-hexanol, isoamyl acetate, 2-methylbutyl acetate, and ethyl sorbate), when added singly to the mixture at the same concentrations tested in the field, decreased the attraction of SWD to the mixture of acetic acid and ethanol. The blends composed of the remaining EAD-active chemicals, an 8-component wine blend [acetic acid + ethanol + acetoin + grape butyrate + methionol + isoamyl lactate + 2-phenylethanol + diethyl succinate] and a 5-component vinegar blend [acetic acid + ethanol + acetoin + grape butyrate + 2-phenylethanol] were more attractive than the acetic acid plus ethanol mixture, and as attractive as the wine plus vinegar mixture in both laboratory assays and the field trapping experiment. These results indicate that these volatiles in wine and vinegar are crucial for SWD attraction to fermented materials on which they feed as adults.

Recommendations for monitoring spotted wing drosophila (SWD) Drosophila suzukii (Matsumura) are to use either vinegar or wine as a bait for traps. Traps baited with vinegar and traps baited with wine, in field tests in northwest Oregon, captured large numbers of male and female SWD flies. Numbers of SWD trapped were significantly greater with a mixture of vinegar and wine compared with vinegar alone or wine alone. Attraction of SWD to vinegar and wine may be due in part to responses to acetic acid and ethanol evaporated from the two baits, respectively. Numbers of SWD captured in traps baited with 2% acetic acid in water were significantly greater than in unbaited traps, indicating a fly response to acetic acid. Very few flies were captured in traps baited with 10% ethanol in water. Traps baited with a combination of acetic acid and ethanol in water captured more SWD flies than traps baited with acetic acid or ethanol solutions alone. These results indicate a synergy of the two materials, and of the two chemicals, as lures for SWD. A comparison of a mixture of acetic acid with ethanol in water versus a mixture of vinegar with wine showed stronger fly attraction to the vinegar/wine mixture, indicating potential attractiveness of vinegar and wine volatiles in addition to acetic acid and ethanol.

These results indicate that acetic acid, ethanol, acetoin and methionol are key olfactory cues for D. suzukii when attracted to wine and vinegar, which may be food-finding behavior leading flies to fermenting fruit in nature. It is anticipated that this four-component blend can be used as a highly attractive chemical lure for detection and management of D. suzukii. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

No abstract

Baits – fermented food products – are generally attractive to many types of insects, which makes it difficult to sort through non‐target insects to monitor a pest species of interest. We test the hypothesis that a chemically simpler and more defined attractant developed for a target insect is more specific and attracts fewer non‐target insects than a chemically more complex food‐type bait. A four‐component chemical lure isolated from a food bait and optimized for the spotted wing drosophila (SWD), Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), was compared to the original wine/vinegar bait to assess the relative responses of non‐target insects. In several field experiments in Washington State, USA, it was shown that numbers of pest muscid flies, cutworm and armyworm moths, and pest yellowjackets were reduced in traps baited with the chemical lure compared to the wine/vinegar bait. In other field experiments in the states of Washington, Oregon, and New York, numbers of non‐target drosophilid flies were also reduced in traps baited with the chemical lure relative to wine/vinegar bait. In Washington, numbers of Drosophila melanogaster Meigen and Drosophila obscura Fallen species groups and Drosophila immigrans Sturtevant were reduced in the chemical lure traps, whereas in New York, D. melanogaster and D. obscura species groups, D. immigrans, Drosophila putrida Sturtevant, Drosophila simulans Sturtevant, Drosophila tripunctata Loew, and Chymomyza spp. numbers were reduced. In Oregon, this same effect was observed with the D. melanogaster species group. Taken together, these results indicate that the four‐component SWD chemical lure will be more selective for SWD compared to fermentation baits, which should reduce time and cost involved in trapping in order to monitor SWD.