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Purple Traps and the Emerald Ash Borer
Emerald ash borer (EAB) is a serious invasive pest of ash trees (Fraxinus sp.). This insect is native to Asia and attacks all species of ash in North America. Our native ash species have no defenses against the EAB and most die within a few years of attack. Emerald ash borer was first found in Michigan in 2002, and since then has spread rapidly throughout the eastern part of the continent (map). Although EAB can spread up to several miles a year on its own, much of the spread can be linked to the movement of infested firewood. Emerald ash borer has killed millions of trees in the last several years, and has the potential to eliminate ash in North America.
When EAB was found in Michigan in 2002, very little was known about the insect. It is said that there was a single two-page publication with details about the biology of the beetle. Now, there are volumes of knowledge about the pest and its interactions with North American forest and ornamental trees. With new understanding of the beetle and its natural history we gain insights into different approaches to managing the insect. Therefore the recommended management techniques can change dramatically in just a couple of years.
In order to reduce impacts, slow the spread of this insect and buy time for development of management solutions, we need to know where it is. Therefore, the Maine Forest Service participates in a trapping program to detect EAB, manages a biosurveillance program and contributes to a large effort to raise public awareness about the insect.
Purple prism traps are one EAB detection method employed in Maine. The other methods for looking for EAB, such as creating trap trees and using biosurveillance, are also very effective techniques, but traps are most efficient for a widespread detection effort.
Extensive research has gone into developing a highly attractive trap and lure combination to aid officials with early detection. Researchers in Tennessee discovered that the color purple was most attractive to EAB.
The traps are made of corrugated plastic and fold into a prism shape. A scented lure, which is a combination of manuka oil and a leaf-blend compound, is hung inside the trap. The outside surface is covered with a sticky glue. The trap is hung in the canopy of ash trees. The color and scent of the trap attract flying adult beetles, which then get stuck in the glue.
Maine began participating in a national purple trap survey program in 2007. The number of traps hung in Maine has increased as EAB has been detected closer to our borders. In 2011, 200 traps were deployed in Maine. In 2012, more than 955 traps were hung across the state with the majority in Oxford and Franklin Counties. The program is made possible by USDA APHIS, PPQ and cooperator resources. The Maine Forest Service, Maine Department of Agriculture, Penobscot Nation Department of Natural Resources and USDA APHIS, PPQ all played roles in conducting the Maine survey in 2012. Maine Forest Service and its partners plan to deploy more than 850 traps in 2013.
Perhaps the best tool for invasive insect detection is public awareness. Please learn more about EAB, and keep your eyes open for signs of its presence. If you think you've found it, please let us know.
Approximate Timeline for 2013 Purple Trap Survey in Maine:
December 2012: Locations of grid cells identified through US Forest Service modeling efforts shared with the states. Emerald ash borer would be found beneath the bark this time of year. Woodpecker damage picks up this time of year, and can be an important clue in locating infestations of emerald ash borer.
January 2013: Maine Forest Service and its cooperators began locating trees in the selected grid cells and seeking landowners' permissions to deploy traps. Cold winter temperatures will not control emerald ash borer. They are protected under the bark of the tree and are adapted to cold climates.
May-June 2013: Traps to be deployed by Maine Forest Service; Maine Department of Agriculture, Plant Health; USDA APHIS, PPQ;and Penobscot Nation Department of Natural Resources. We expect adult flight period would begin in ~mid June in Maine--as the adult leaves the host tree a characteristic "D" shaped exit hole is created. Many of the little green beetles people turn in beginning in early May are tiger beetles (image below). They are beneficial, they prey on other insects including many pest species.
July - August 2013: Traps will be checked for emerald ash borer and lures replaced. Emerald ash borer adult flights, mating and egg laying activity peaks. Activity of the ground nesting wasp that preys on metallic wood boring beetles (including emerald ash borer) is apparent by mid-July.
September-November 2013: Traps will be removed and checked for emerald ash borer. Adult beetle flights would be largely over. Larvae hatched from eggs deposited on the bark of ash trees would be creating meandering tunnels beneath the bark as they feed on nutrient rich inner bark and phloem.
The following Web sites have more information about emerald ash borer, reporting sitings, and the national purple trap program:
www.maineforestservice.gov/InvasiveThreats.htm (Maine Forest Service)
www.maine.gov/eab (Maine Department of Agriculture, Plant Health)
www.purpleEABsurvey.info (USDA APHIS, PPQ)
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