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 be as devastating to ash as the chestnut blight was to American Chestnut.
Traps are one tool used to look for EAB in Maine. 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.
Traps for EAB come in a variety of colors and shapes, but the most commonly used trap in Maine is the purple prism trap provided through cooperation with USDA APHIS. Maine has been participating in a national purple trap survey program since 2007. In recent years, most traps have been deployed by A USDA APHIS contractor.
A Year in Maine’s Purple Trap Survey in Maine:
January-April The approach to the survey for the coming spring is planned. Supplies are ordered to arrive ahead of the need. Emerald ash borer would be found beneath the bark this time of year. 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: Ideally, traps are deployed before the start of the adult flight season. We expect adult flight period would begin in ~mid June in southern 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: 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-October: 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.
November-December: Woodpecker damage picks up this time of year, and can be an important clue in locating infestations of emerald ash borer.
For more information on emerald ash borer in Maine visit www.maine.gov/eab.