Iowa State University Extension has been on the lookout for the emerald ash borer, Agrilus planipennis. This exotic beetle from Asia infests healthy ash trees, as well as ones that are weak or dying. Researchers have not identified ash trees resistant to emerald ash borer (EAB) attack. More than 25 million ash trees have died from EAB in the Midwest. Iowa has an estimated 55 million ash trees in rural forests and 20 million in urban settings.
EAB Infested Areas. EAB has not yet been found in Iowa. The closest known infested site is Peru, Ill., approximately 85 miles east of Davenport. The epicenter of EAB is Detroit, Mich. where it is thought this beetle was brought in on infested wood crating. EAB has spread throughout Michigan and to sites in Illinois, Indiana, Maryland, Missouri (extreme SE), Ohio, Pennsylvania, Wisconsin (just below Milwaukee) and West Virginia. Click here for the latest distribution map from USDA. These areas are under federal quarantine to limit the movement of this destructive pest. On their own, EAB adults can fly one to two miles. Long-distance expansion of this pest has unintentionally occurred by moving infested containerized ash trees and ash wood product, of which firewood is the major culprit.
The Damage Done. Although adult EAB beetles feed on ash leaflets, it is the larval stage that kills trees. These creamy white, flattened larvae feed just under the bark in the nutrient-rich cambium tissues. As they feed, they produce winding tunnels that cut across the active xylem and phloem vessels, which carry water, minerals, and nutrients throughout the tree. The parts of the tree beyond an EAB-infestation slowly starve and die, usually within two to four years.
2008 Surveillance. ISU Extension canvassed Iowa during 2008 in collaboration with the Iowa Department of Agriculture and Land Stewardship, Iowa Department of Natural Resources Forestry, U.S. Department of Agriculture (USDA) Forest Service and USDA Plant Protection Quarantine program. At 235 high risk sites (private and public campgrounds), 1270 trees were visually inspected for signs of EAB symptoms. 652 sticky traps were placed in ash tree canopies during adult EAB flight period; all traps were negative for this beetle. More than 400 sentinel trees were removed this fall and contractors are in the process of removing the bark to look for signs of EAB.
What You Can Do To Prepare
- Determine if you have ash trees. See Identification of Common Trees in Iowa
- Protect your trees from mechanical injuries (lawn mowers, trimmers, construction, and vehicle parking on root zone)
- KNOW the symptoms of EAB activity:
- Thinning and dieback of branches
- Water sprouts on the trunk or main branches
- D-shaped exit holes in the bark
- Flattened white larvae found feeding under the bark and producing serpentine tunnels
- Dark, metallic green beetles (1/2 inch long) on or near ash trees
- REPORT suspect ash trees or beetles to ISU Extension Entomology (515) 294-1101 or the State Entomologist (515) 725-1470
- Encourage governmental officials to make EAB preventive efforts a priority
- Use only local firewood
- Do not apply preventive insecticide treatments at this time. See HHPN April 9, 2008 for more detail.
- Learn more at Pest Management and the Environment or http://www.emeraldashborer.info/
This article also appeared in the January 2009 issue of ISUE Acreage Living, a monthly newsletter for rural residents highlighting timely topics on country living, available on-line.
Adult emerald ash borer. Photo from www.EmeraldAshBorer.info