WILLMAR -- The Willmar Public Works Department, with help from the Minnesota Department of Agriculture, has been on the lookout this summer for the emerald ash borer that has killed millions of ash trees in 13 states including Minnesota, and parts of Canada.
So far, there's been no sign locally of the pest. The adult is bright, metallic green and measures half an inch long and one-eighth of an inch wide. The larvae are creamy white, flat and legless.
"We haven't found anything here yet,'' says Scott Ledeboer, public works foreman, looking at an emerald ash borer trap placed at Lions Park by the Department of Agriculture. "They are destructive if they get hold of an ash tree. We have a lot to be concerned about here because we have a lot of ash trees. They're a good tree. They grow almost anywhere.''
Officials believe the emerald ash borer was accidentally introduced into North America from Asia in ash wood used for stabilizing crates in cargo holds. Before the borer was discovered in Michigan in 2002, it had never been found in North America. It has now spread through Illinois, Indiana, Kentucky, Maryland, Missouri, New York, Ohio, Pennsylvania, Virginia, West Virginia and Wisconsin, and in Ontario and Quebec in Canada.
This year it was found in Minnesota and the Agriculture Department has quarantined the movement of ash wood in Hennepin, Ramsey and Houston counties. Minnesota has the second-largest concentration of ash trees in the country.
Willmar had been planting ash trees, along with other varieties, to replace diseased elm trees and for new plantings around town, but stopped planting ash trees in 2007.
The trap at Lions Park is one of four placed this past spring by the Agriculture Department around Willmar to detect the pest. The department will collect the traps this month and examine any insects inside.
In Kandiyohi County, the department hung a trap near the southeast corner of Nest Lake and three in the North Long Lake area.
The department also placed traps in other parts of the state, including seven in Pope County, seven in Meeker County, two in Lac qui Parle County and one in Renville County, according to the department's emerald ash borer Web site.
The interior of each trap -- made in the shape of a triangle -- contains a sticky purple substance meant to attract and hold the emerald ash borer. The insect is drawn to the color "and when they hit it, they stay there,'' said Ledeboer.
The emerald ash borer can fly only short distances in its lifetime on its own. The biggest concern is moving ash wood where the emerald ash borer can ride either in the adult or larval stage.
"The number one way (emerald ash borer) moves to new areas is when people accidentally help it spread by moving infested wood products like ash limbs or firewood,'' says Geir Friisoe, Agriculture Department plant protection director. "Since we implemented the quarantine earlier this year, we've been pleased to see strong support from Minnesotans in the affected counties. They understand that the choices they make help strengthen our efforts to control this pest.''
Evidence suggests the insect is generally established in an area for several years before it is detected, according to the U.S. Department of Agriculture.
Larval feeding in the tissue between the bark and sapwood disrupts transport of nutrients and water in a tree, eventually causing branches and the entire tree to die. Once an ash is attacked, the tree will be killed. After one to two years, the canopy of the tree begins to thin. Most of the canopy will be dead and bare within the first few years from when symptoms are observed.
Some ash trees push out sprouts from the trunk and roots, called epicormic shoots. The leaves are often far larger than normal-size leaves in the canopy. Woodpeckers like the larvae; heavy woodpecker damage could be a sign of infestation. Small holes also exist on infested trees: they are D-shaped and roughly one-eighth inch in diameter. This is where the newly adult borers emerge from the tree.
If a dead tree is located in a yard or along a street, it will likely pose a threat over time and should be immediately removed. If removed, maple trees are suggested for easy replacement. However, if the tree is within a woodlot or similar area, these trees can provide valuable wildlife habitat. Standing dead trees are an integral part of a healthy ecosystem.