Emerald Ash Borer What Does Emerald Ash Borer Look Like? For most of the year, EAB is concealed from view, feeding as larvae inside an ash tree. Larvae pupate into adult beetles, which begin emerging in mid-May. A beetle is bullet-shaped and only about one-half inch long and one-eighth inch wide. It has very short antennae. With its wings closed, a beetle is dark metallic green on top and bright emerald green underneath. When its wings flare, a violet-colored abdomen becomes visible. Adults typically live three to six weeks, foraging on ash leaves, then mate and die. They are harmless to humans. Photo Credit: David Cappaert, Photo Credit: Howard Russell, Michigan State University, Bugwood.org Michigan State University, Bugwood.org Where Did Emerald Ash Borer Come From? EAB is native to northern China, eastern Russia, Korea, and parts of Mongolia and Japan. It lives in upland and lowland forests inhabited by species of ash trees native to those countries. Ash species there, unlike here, evolved alongside EAB and became equipped with chemical defense compounds targeted against it. In its native range, EAB attacks only trees in poor condition, weakened by drought or other causes, which are unable to produce sufficient amounts of these compounds. When and How Did Emerald Ash Borer Get To The United States? Nobody is certain exactly when and how EAB got here. It was first found in North America in 2002 in suburban Detroit. Approximately half a million ash in the Detroit and Windsor, Ontario areas were dead by then, so experts believe EAB had been present for about a decade. EAB likely arrived as larvae in shipping containers made from ash being used to transport heavy consumer products from Asia. How Does Emerald Ash Borer Kill an Ash Tree? Although adult beetles forage on ash leaves to survive, this does not kill a tree. Larvae hatch from eggs deposited in the bark on branches or trunks of live ash trees. They bore inward and feed on the phloem, a thin layer encircling the tree just under the bark. The phloem distributes food manufactured by leaves from photosynthesis. To a lesser extent, larvae also feed on outer sapwood, a layer of cells that conducts water and nutrients upward Photo Credit: David Cappaert, from the roots. This feeding disrupts food, water, and nutrient movement, eventually killing a tree. The presence of larvae or their Michigan State University, Bugwood.org telltale S-shaped excavation “galleries” pictured provides conclusive confirmation of an EAB infestation. Depending on size and condition, a tree will die in one to five years from EAB. Why Is Emerald Ash Borer So Destructive? EAB prefers green ash (Fraxinus pennsylvanica) and black ash (Fraxinus nigra) but will also readily kill white ash (Fraxinus americana) and blue ash (Fraxinus quadrangulata). Scientists have no reason to believe any native North American ash species is not at risk. EAB attacks and kills ash trees regardless of location: in Photo Credit: James W. Smith, USDA forested areas, in fencerows and windbreaks, in nurseries, APHIS PPQ, Bugwood.org along city streets, in city parks, and in yards. EAB attacks healthy trees. It goes after weakened or stressed trees first but then quickly moves to healthy trees. The chemical defenses in North American ash evolved to repel its natural enemies, not emerald ash borer. Emerald ash borer attacks any size ash tree, from nursery-size to full-grown. EAB does not attack mountain ashes. So named only because of their ashlike leaves, mountain ashes are not true ashes. They belong to the genus Sorbus whereas true ashes belong to the genus Fraxinus. American mountain ash (Sorbus americana) and showy mountain ash (Sorbus decora) are native to Wisconsin. Both occur in Dane County but are more common northward. Mountain ashes planted as ornamental yard trees, however, are typically nonnative species. Two sold in this area are European mountain ash (Sorbus aucuparia), known European mountain ash commonly as “rowan tree,” and Korean mountain ash (Sorbus alnifolia). Both reach 20–40 feet in height and Photo Credit: Bob Dunlap, Gustavus Adolphus College feature cream-colored flowers in the spring and orange-red berries in the fall. For helpful pictures and descriptions of these two trees, go to www.hort.uconn.edu/plants. Why Is Emerald Ash Borer Spreading So Fast? In Russia and Asia, tiny, stingless wasps and other natural predators keep EAB in check. Likewise, native North American ash borers are kept in check by wasps and natural predators here. Scientists, however, have not found any evidence that they attack EAB. Woodpeckers drill for EAB larvae in the winter, but not enough to contain its spread. A female beetle will lay 60–90 eggs before dying. Scientists estimate that the EAB population in North America increases tenfold each year. EAB has a widespread rural food supply. Green ash and white ash are plentiful in forests throughout the South, East, and Midwest and extend into the Great Plains. Black ash is abundant in the Northeast and Upper Midwest. Maine, New York, and Minnesota each are estimated to have approximately 900 million ash trees. Wisconsin and Michigan are estimated to each have more than 700 million. EAB has a widespread urban food supply. In Wisconsin, on average, one in every five street trees—trees planted between sidewalks and streets, in boulevard medians, and in other road right-of-ways— is an ash. Elms lost to Dutch elm disease were most often replaced with green ash. Green and white ash (which also has been overplanted) grow fast, thrive in a variety of climates, and tolerate urban conditions. Humans have accelerated the spread of EAB through transport of firewood, nursery trees, and other wood products. Research has found that EAB beetles typically fly no farther than a couple of miles. Quarantines restricting movement of firewood, ash nursery trees, and ash logs have not curtailed the spread of EAB. Three-quarters of the infestations detected in 2005 were in parks or campgrounds. Outlying infestations in Missouri and West Virginia are likely due to firewood transport. EAB traveled from Michigan to Maryland in a shipment of infested ash nursery trees. How Is Emerald Ash Borer Detected in Wisconsin? The Department of Agriculture, Trade, and Consumer Protection (DATCP) sets regulations and implements procedures for controlling the spread of EAB. DATCP initially used the “cut-and- peel” method to look for EAB. During falls and winters from 2006 to 2009, workers cut approximately 2,900 ash trees and peeled off trunk bark to look for EAB larvae or their excavation tunnels. Most of the trees examined were in highway right-of-ways in the southern half of the state. No larvae or excavation damage was found. In 2008, DATCP switched to a hanging trap (pictured) that employs a chemical attractant to lure EAB beetles. It hung approximately 3,600 statewide, mostly along highways and in public parks. In 2009, 6,900 traps were hung. Photo Credit: Wisconsin DATCP How Large Are the EAB Infestations in Wisconsin? As of September 2009, EAB beetles or larvae have been found in seven Wisconsin counties: Ozaukee and Washington in 2008 and Vernon, Crawford, Brown, Kenosha, and Milwaukee in 2009. WI Quarantine Locations DATCP is conducting detailed surveys in these areas to gauge how widespread EAB is. The infestation straddling Ozaukee and Washington Counties thus far appears to be the largest. Surveyors working outward from Newburg in Washington County have found larvae in ash trees approximately one mile to the south, east, and west and one and a half miles to the north. The infestation could be dispersed across 5,000 acres and threaten an estimated 50,000 trees. Forest stands in the area contain 20 to 85 percent ash. Tree core analysis determined that the infestation began as early as 2004. Ongoing survey work in Vernon County thus far indicates that infestation also could encompass a large area. Infested trees have been found a mile or more north, south, and east of Victory, a small town about 20 miles south of La Crosse, where EAB was first detected in the County in April 2009. Beetles were then found about six miles south of Victory in July 2009 in a trap in Crawford County. EAB has been detected at three locations in Milwaukee County: first in August 2009 in Franklin, just southwest of Milwaukee, and then twice in November 2009 about two miles to the east in Oak Creek. Shortly after DATCP surveyors, performing follow-up work in Oak Creek, found an infestation, EAB was confirmed in another tree about one-third of a mile away on private property. DATCP will continue surveying that area of the County through the winter and increase the number of traps there next summer to gauge how widespread EAB is. As of December 2009, DATCP surveyors have not found outlying infestations in Brown County, where EAB was detected in a Green Bay, and in Kenosha County, where it was found in eastern Kenosha. Surveyors will continue systematically looking for outlying trees exhibiting EAB symptoms and confirm its presence by finding larvae or excavation tunnels. Next summer, DATCP will hang several traps around both locations to search for adult beetles. Left to right: ashes attacked by EAB on private property in Newburg, an ash infested with EAB in a Newburg park, and two dead ashes along the Mississippi River near Victory in Vernon County. (Photo credits: Mick Skwarok, Wisconsin Department of Trade, Agriculture, and Consumer Protection) How Is DATCP Trying to Slow the Spread? Healthy ash given preemptive, long-term insecticide treatment may survive EAB. But this is not an option for widespread control.