What Is That Purple Thing?

Have you seen a strange purple triangular thing hanging in a tree? Is it a stranded kite, a decoration, a CIA listening device, an alien from outer space? No, it's a "purple trap" for emerald ash borer beetles. It was placed in that ash tree as part of a U.S. Department of Agriculture project to determine the leading edge of known emerald ash borer infestations and to locate other outlying emerald ash borer populations. The survey, conducted in 48 States, will use approximately 60,000 detection tools or “traps” throughout the country.

The emerald ash borer (EAB) is a small, metalic-green, wood-boring beetle that was discovered in southeast Michigan in 2002. The natural range of the emerald ash borer is eastern Russia, northern China, Japan, and Korea. It was suspected to be accidentally imported to North America from China in the 1990s and has since destroyed more than 30 million ash trees in southeastern Michigan alone.

Since its discovery, the emerald ash borer has been detected in six other States — Illinois, Indiana, Maryland, Ohio, Pennsylvania, and West Virginia. Federal and State quarantines have been established in these States to mitigate the spread of the insect. Quarantines prohibit the movement (within the State and out of the State) of regulated articles, which include ash nursery stock, green ash lumber, pallets, branches, stumps, etc., and all hardwood chips and firewood.

The States of Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, New York, Ohio, Pennsylvania, West Virginia, and Wisconsin will participate in a delimiting survey within a 100-mile band of known EAB infestations. These States will deploy purple traps in a 1.5-mile by 1.5-mile grid where ash is found growing. Granville is located within a survey area.

The remaining States will participate in a risk-based survey where purple traps will be placed in ash trees at high-risk locations such as in campgrounds, recreational areas, saw mills, nurseries, and new commercial/residential developments.

Ohio has 3.8 billion ash trees and to date, infestations have been identified in Allen, Auglaize, Butler, Cuyahoga, Defiance, Delaware, Erie, Fairfield, Franklin, Fulton, Hamilton, Hancock, Hardin, Henry, Huron, Logan, Lorain, Lucas, Mahoning, Marion, Medina, Mercer, Miami, Montgomery, Ottawa, Paulding, Portage, Putnam, Sandusky, Seneca, Union, Warren, Williams, Wood, and Wyandot counties.

The EAB survey is funded by USDA. Each participating State has submitted a cooperative agreement and work plan to determine resources necessary to successfully complete the survey.

The trap is a three-dimensional triangle or prism. It’s made out of thin, corrugated, purple plastic that has been coated with non-toxic glue on all three sides. The purple prisms are about 24 inches long and hang vertically in an ash tree or are secured to the trunk of a tree. To increase the attractiveness of the trap to the beetles, it is baited with a lure (Manuka oil).

For many insects, color frequently plays an important role, and the EAB is no exception. In 2003, researchers began investigating the EAB to develop an effective detection tool. Scientists from Tennessee State University (TSU) found that buprestids (the insect family to which EAB belongs) in general are more attracted to red and purple hues compared to other colors. Therefore, researchers initiated a study using a variety of red and purple traps to determine which trap attracted the most beetles; the purple trap achieved the best results.

To improve the purple traps’ attractiveness to EAB adults, they are baited with oil from the Manuka tree. Researchers found that there are four active compounds in Manuka oil that are also produced when an ash tree is girdled or stressed. In field tests when baited traps and non-baited traps were compared, traps baited with Manuka oil attracted more beetles than traps that were not baited.

The lifecycle of EAB is dependent upon the Ash tree, its only known host. The adults feed on the leaves, lay eggs in its crevices, and the larvae develop under its bark. All ashes (green, white, black, etc.) are EAB hosts.

The purple traps have been placed in ash trees this spring before the EAB adults emerged. The traps will be monitored and remain in place throughout the summer during the beetles’ flight season. This fall all traps will be removed.

The purple traps pose no risk to humans, pets, or wildlife; however, the non-toxic glue can be extremely sticky and messy if touched.

During EAB adult emergence, beetles fly around ash trees, nibbling on leaves and looking for a mate. If an EAB lands on a purple trap, it will get stuck in the glue. Mid-summer survey crews will visit trapping sites to refresh lures and collect any insects stuck on the traps. In the fall, crews will return to trap sites a second time to collect samples and remove the traps.

Purple traps do not attract or pull beetles into an area. The traps are a detection tool to help find EAB if it is present in the area.

The insect samples collected from the traps will be cleaned and sent to a USDA identifier for verification. All verifications of EAB will be communicated to the appropriate Ohio plant regulatory officials.

The fact that traps are located in Granville does not mean EAB is here; it means officials are looking for the beetle. The goals of the 2008 EAB Survey are to define the leading edge of the infested area and to locate new outlying EAB infestations.

Survey traps will be in ash trees throughout the summer; the public is being asked to please not disturb them. If you see a purple trap on the ground, please contact the Ohio Department of Agriculture at 1-888-OHIO-EAB. You can also call the USDA EAB Hotline at 1-866-322-4512.