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Iowa may be an island in emerald ash borer storm Tuesday, June 23, 2009
Agri News staff writer
ELKADER, Iowa -- Donald Lewis had good news at last week's emerald ash borer meeting at the Opera House in Elkader.
"Despite dozens of people looking for evidence of emerald ash borer at the Osborne Nature Center where a larva was reportedly found and submitted to the Iowa Department of Natural Resources, as far as anyone knows, no infestation has been found," said Lewis, who is an entomologist at Iowa State University. "But since infestations have been found in central Illinois, St. Paul, Minn., and across the Mississippi River from Allamakee County in Victory, Wis., it's not a question of if, but when."
Lewis said tree owners need to be concerned about the small insect because it attacks and kills ashes. All North American ash trees are susceptible.
Emerald ash borer is native to parts of Russia, China, Japan, North and South Korea and Taiwan and was accidentally introduced into the Detroit area likely through some type of crating material. It was first discovered in Michigan in 2002, but was likely there for about 10 years before that, Lewis said.
Emerald ash borer is now found in Michigan, Ontario, Maryland, West Virginia, Ohio, Illinois, Wisconsin, Minnesota and southern Missouri.
"Iowa is like a hole in the middle of a donut," Lewis said. "Emerald ash borer infestations have been found in all the states around Iowa."
EAB has spread through transporting firewood, lumber products and nursery stock, Lewis said.
The larvae chew through ash bark and into new wood. It cuts off circulation and kills the tree. The larva is 1 to 1.25 inches long, although it starts much smaller. The larva leaves "S" shaped tunnels that wind back and forth and become progressively larger as the larva grows. Prepupal larvae overwinter in shallow chambers excavated in the outer sapwood or bark. Pupation begins in late April or May with new adults emerging through small D-shaped exit holes. The adult beetles emerge in June and July and are present into mid-August.
Symptoms of infected trees include a thinning canopy, sprouts where there should not be sprouts, woodpecker feeding, bark splitting and damage from larval feeding.
"As lots of larvae attack the tree, the overlapping tunnels girdle the tree," Lewis said.
The Iowa Department of Agriculture and Land Stewardship in conjunction with the USDA has placed purple sticky traps in stressed ash trees throughout Clayton County to determine if EAB is actually in Iowa. Lewis said that early detection of EAB and efforts to slow its spread are the strategy to control it.
Insecticides can protect trees. The chemicals are injected into the soil or the tree trunk. The treatment will have to be continued annually. Lewis said ISU Extension doesn't recommend treating a tree unless an infestation has been reported within 15 miles of the tree.
"Treatment is not practical or cost effective for woodlot trees," Lewis said. |
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