A blend of odors that attracts spotted wing drosophila flies (SWD) has been developed into a new lure product for improved monitoring and control of these tree-fruit and berry pests.

The blend is a combination of four different chemicals found in the aromas of both wine and vinegar. U.S. Department of Agriculture (USDA) entomologist Peter Landolt and research associate Dong Cha, along with their Oregon Department of Agriculture colleagues, isolated the chemicals and evaluated them extensively in laboratory and field trials.

Based on those findings, Trece, Inc., in Adair, Oklahoma, commercially formulated the compounds into a novel blend and controlled-release lure, which is marketed under the trademark "PHERO-CON SWD," along with a related trap.

According to Landolt, with USDA's Agricultural Research Service (ARS) in Wapato, Washington, farmers and pest managers need improved methods of attracting, monitoring and managing the flies to prevent potential losses of cherries, berries, grapes and other fruit crops. The lure's availability should provide growers with better information to use in making pest-management decisions, such as where, when or whether to spray.

Left unchecked, female SWD flies deposit their eggs beneath the surface of host fruit, where subsequent larval feeding causes it to soften, bruise and wrinkle, notes Landolt, who is in the ARS Fruit and Vegetable Insect Research Unit at Wapato.

Capturing SWD with lures containing wine and vinegar isn't a new approach. But Landolt's group was first to conduct a top-down examination of which chemical constituents in the liquids' aromas attract specifically these flies.

In extensive testing, they showed that ethanol alone was less attractive than wine, and acetic acid alone was less attractive than vinegar. Similarly, combinations of ethanol and acetic acid were also less attractive to the flies than wine-plus-vinegar blends, which suggested that other constituents were at work. Of 20 total Chardonnay wine and rice-vinegar chemicals the researchers evaluated, acetoin and methionol triggered the strongest responses in the flies when combined with acetic acid and ethanol.

ARS is USDA's chief intramural scientific research agency, and this research supports the USDA priority of promoting international food security.