Wasp and vespiary
The European paper wasp. (File photo)

Research to find the best lure for trapping the spotted wing drosophila serendipitously put Dr. Peter Landolt on the scent of a ­better way to deal with paper wasps.

Landolt and colleague Dr. Dong Cha, who are based at the U.S. Department of Agriculture’s laboratory in Wapato, Washington, developed a new lure for spotted wing drosophila. Scientists in Mississippi, who are cooperating in the project, tested the new lure alongside a standard bait of wine and vinegar to trap spotted wing drosophila in blueberries. They found that the wine and vinegar ­mixture also attracted lots of paper wasps.

This caught Landolt’s attention because of a project he’s been working on for the U.S. Air Force to find a way to control paper wasps in air traffic control towers. It also happens that another species of paper wasp, Polistes dominula, can be a troublesome pest in cherry orchards and vineyards in the Pacific Northwest.

The European paper wasp Polistes dominula is a late-season pest of cherries. Photo courtesy of Duane Holder

Landolt’s experience with wasp attractants goes back to the late 1980s, when he worked for the USDA’s Agricultural Research Service in Gainesville, Florida. He had a project funded by the National Aeronautical and Space Administration to rid the space shuttle launch pad of swarming wasps. Paper wasps tend to aggregate in the fall around elevated structures, such as treetops, towers, and high-rise buildings. At Cape Kennedy, female wasps had aggregated to overwinter inside a mechanical room at the top of a 490-foot-high launch tower. Male wasps swarmed around the outside of the room to intercept the females and mate with them, and in the process were alarming employees working on the tower. This happened during a period when there had been a dearth of shuttle launches.

Before Landolt and his colleagues were able to find a solution, NASA launched a shuttle. Since the whole launch pad goes up in flames as a shuttle lifts off, the problem was solved.

Air traffic control

More recently, Landolt has been working on a similar project for the U.S. Air Force, which has a wasp problem at its air traffic control towers. Wasps are attracted to the towers, which in the southeastern United States tend to be the tallest structures on the horizon. Landolt said the design of the towers makes it easy for wasps to find their way inside the towers and into the control rooms. For the most part, the wasps that get inside the tower are the females that sting.

“If you’ve got somebody at a panel watching radar of aircraft coming and going, coming and going, and they’ve got wasps crawling on them and walking across the screen, it can be unnerving,” he said.

Landolt said he and his colleagues have been working to develop a chemical attractant for those wasps so they can be trapped. Traps for yellowjackets, which he ­previously developed, don’t work well for paper wasps.

A breakthrough came a couple of years ago when Landolt learned that those wine and vinegar traps being used in the spotted wing drosophila tests in Mississippi were attracting large numbers of Polistes metricus and P. bellicosus paper wasps, even though they’d not been noticed flying around. This was intriguing, given the dearth of useful baits and attractants known for paper wasps. It was the first indication of a useful bait for ­trapping paper wasps.

Field tests at Moody Air Force Base in Georgia, Shaw Air Force Base in South Carolina, and the University of Florida, Gainesville, confirmed that wine and vinegar baits attracted paper wasps.

However, in lab tests, when wasps were exposed to wine and vinegar separately, they preferred wine. They were attracted to ethanol (a major volatile of wine) and deterred by acetic acid (a major volatile of vinegar), which Landolt found somewhat surprising. ­Yellowjackets, which are related to paper wasps, are attracted to acetic acid combined with isobutanol.

The wasps’ orientation to fermented baits is likely to be food-finding behavior that they use in nature to locate fermented sweet materials. In the field, paper wasps feed on carbohydrate-rich foods such as fruit, sap, honeydew of sucking insects, and plant nectaries. As a sweet fruit product ages, it ferments first to alcohol and then to vinegar. Landolt said it could be that the paper wasp’s preference for alcohol matches up with its preference for natural food sources that have not aged too much.

Based on these results, Landolt and Cha worked in the lab to isolate and identify volatile chemicals in wine that are particularly attractive to the wasps and could be used as a lure. This spring, they sent out an experimental lure
containing a combination of volatiles that they identified to test on paper wasps in Florida, Georgia, Mississippi, Texas, and South Carolina.

Meanwhile, the researchers have done lab tests with P. dominula, the species that attacks cherries and grapes in the Pacific Northwest, to find out how it reacts to wine and vinegar.

Landolt said P. dominula, known as the European paper wasp, is generally only a problem in small orchards or vineyards with nearby buildings that provide enclosed nesting places for the wasps. The insects commonly nest under eaves or within enclosed spaces such as in meter boxes, inside pipes, or between shakes.

“They generally don’t nest out in the field or orchard,” he said.

Paper wasps are not usually a big problem in cherries, other than in late districts, because the fruit is picked before populations explode in the late summer.

Landolt said P. dominula is often confused with yellowjackets, but the wasps need to be accurately identified because of paper wasps not being attracted to yellowjacket traps.