Drosophila suzukii, a small fly also known as spotted wing drosophila, is an invasive pest of several fruit crops. A new study on chemical lures for trapping and monitoring the insect has optimized a formula for significantly greater attraction. (Photo credit: Hannah Burrack, North Carolina State University, Bugwood.org)

To slightly modify an old adage, you can catch more flies with increased levels of acetoin, acetic acid, and ethanol than with methionol.

Specifically, the fly in question is spotted wing drosophila (Drosophila suzukii), an invasive pest in North American and Europe that attacks several fruit crops. A lure for catching and monitoring in D. suzukii populations was developed in 2014 using four chemicals from wine and vinegar, and now a team of researchers has tinkered with relative levels of those chemicals in the lure to double its attractiveness. Their research was published this week in the journal Environmental Entomology.

“The advantage of the use of these specifications is a potential significant improvement in the power of the lure, which should translate to the ability to detect a smaller population density, detect a population earlier in the season, or to kill a higher percentage of a population with baits,” says Peter Landolt, Ph.D., entomologist at the USDA-Agricultural Research Service and co-author of the study with Dong Cha, Ph.D., at USDA-ARS and Todd Adams, Ph.D., at the Oregon Department of Agriculture.

The researchers conducted a series of experiments that varied the levels and release rates of the four chemicals in the existing lure—acetic acid, ethanol, acetoin, and methionol—to find the optimal concentrations of each for attracting spotted wing drosophila (SWD). They found that increased amounts of acetic acid, ethanol, and acetoin enhanced the lure’s performance, but increased methionol had no effect. In particular, increasing both acetic acid and acetoin resulted in higher attraction than did increasing either alone, suggesting a “synergistic interaction” between the two.

Combining all the results, the researchers arrived at an optimum formula that caught 104 percent more SWD males and 147 percent more SWD females than the original formula.

“The results provide a set of criteria or specifications for providing a superior attractant, compared to that developed previously,” Landolt says. “That is, we produced a much stronger lure that should be valuable to pest managers for detecting or controlling SWD.”