Emerald ash borer found on campus

Falcon Heights is the second city in Minnesota to battle the tree-killing emerald ash borer.

Taryn Wobbema

Beneath the bark of a seemingly healthy ash tree on the University of Minnesota St. Paul campus, state officials found evidence of a second case of emerald ash borer (EAB) infestation. Found on a tree in Falcon Heights, Geir Friisoe, director of the Minnesota Department of AgricultureâÄôs plant-protection division, said the city was lucky to find it as early as they did. Based on the damage to the tree, officials say the beetles have been present for one or two years. The first infestation was found in May in St. Paul, about one mile north of the new case. Cy Kosel, a natural resources manager in St. Paul, said EABs migrate about a mile every year. ItâÄôs estimated that the beetle reached Minnesota in 2006, providing the possibility that infestations will be found up to three miles from the original source. In August, an adult EAB was found in a trap in Falcon Heights. Since then, the city has been moving forward on plans to get ahead of the infestation. Falcon Heights City Administrator Justin Miller said a plan will go before the City Council on Thursday to begin a seven-year plan to remove all the city-owned ash trees, infected or not, and replace them with different trees. The city maintains about 300 ash trees, Miller said. This does not include those on University property. Removal of 40 to 50 ash trees this year will cost the city about $40,000, Miller said. Kosel said St. Paul has also implemented tactics alongside the Department of Agriculture to slow the spread of the tree-killing pests. Eighty infested trees were confirmed this year, and Kosel said that number will likely double each year from now. He estimated that St. Paul has around 1 million trees in the city, 20 percent of which are ash. With that many trees at risk, it is better to spread out the cost and begin uprooting trees now, Kosel said. David Andow, University professor of insect ecology, said emerald ash borers are only about three-quarters of an inch long, and the holes they make in trees measure about a quarter of an inch in diameter. âÄúItâÄôs not a very big beetle,âÄù Andow said. âÄúItâÄôs not easy to find a quarter-inch hole.âÄù Their size makes it difficult to find infested trees until after symptoms become visible. The beetles feed on the vascular tissue of ash trees, slowly starving them to death by preventing nutrients from traveling from end to end, Andow said. When a tree is infested, it must be cut down and ground into small pieces to ensure the larvae are killed. Then the tree is burned. Sticky purple traps have been hung beside trees to attract and capture adult EABs. Friisoe said the beetles like purple. Andow said the University campus has about 600 trees that could be lost if nothing is done. âÄúThis is a major opportunity to help figure out how to control borers in this area,âÄù he said. Entomologists at the University would like to test different ways to control the rising problem. EABs were first found in Michigan in 2002. They have since infested ash tree populations in 12 other states including Wisconsin, Illinois and Missouri.