Emerald Ash Borer
Originally from Asia, the emerald ash borer (Agrilus planipennis) was first discovered in Michigan in 2002. It has since caused widespread tree mortality and decline in ash (Fraxinus spp.) trees in Connecticut, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin. The emerald ash borer is transported mainly by humans through infected nursery stock, firewood, unprocessed saw logs, and other ash products.
The adult emerald ash borers are about 1/2 inch long, 1/8 inch wide, and are bronze, golden, or reddish green with darker metallic green wings. The underside is metallic purple-red. The adults can usually be seen from June to August. The larvae are 1 to 1.2 inches long and are white or cream colored. The larvae make S shaped galleries under the bark of the ash tree. The larvae and galleries can usually be seen year-round. Once the tree is infested and the emerald ash borer population builds, the leaves begin to wilt and branches die leaving a sparse canopy.
D shaped holes, which are 1/8 inch in wide and can be seen year-round, may be noticeable in the branch and trunk where the adult beetles emerged. Early detection is very difficult as it takes 1-3 years of infestation before an ash tree begins to show signs of mortality or decline. Tree mortality is caused when larval feeds on the tissue between the sapwood and the bark thus disrupting the transportation of nutrients and water. This disruption eventually causes the branches to die first followed by the entire tree.
Identify Your Tree: Ash trees are easiest to identify when leaves are on the trees; however, it can be identified by looking at the bark in the wintertime.
- Bark - young bark is usually flaky; forms tall, interlacing ridges and deep furrows with age.
- Autumn color - green ash: yellow and orange; white ash: red and purple.
- Leaflets - either no stalks or very short stalks attached to the leaf stem; smooth or sometimes finely serrated on the upper half.
- Leaves - oppositely arranged on twig, pinnately compound (leaf is made up of several leaflets attached to a leaf stem), and has 5 to 9 dark green leaflets (usually 7 or 9).
- Twigs - stout, gray to green-brown with small, lateral round buds opposite each other; terminal bud is large, brown, with leathery scales flanked by two small lateral buds.
The emerald ash borer (EAB) was identified in Tennessee at a truck stop on I-40 in Knox County in July, 2010. By 2011 six Tennessee counties, Blount, Claiborne, Grainger, Knox, Loudon, and Sevier were under emerald ash borer quarantine. In 2012, 12 more counties were added to the original 6: Anderson, Campbell, Cocke, Greene, Hamblen, Hancock, Hawkins, Jefferson, Monroe, Roane, Smith, and Union. In 2013, 3 additional counties were added: Hamilton, Jackson and Scott. In 2014,18 new counties were added including Davidson, Fentress, McMinn, Morgan, Polk, Putnam, Rhea, Sullivan, and Washington where EAB was positively detected, and Bradley, Carter, Clay, Johnson, Macon, Meigs, Overton, Pickett, and Unicoi where EAB is likely present based on close proximity to positive counties. By October 2015, eight (8) new counties were added and included Bledsoe, Cumberland, Franklin, Marshall, Rutherford, Trousdale, Williamson and Wilson. This brings the total number of counties quarantined for EAB to 47.
County Quarantine Map
USDA Animal and Plant Health Inspection Service, along with the aid of the Tennessee Department of Agriculture, Tennessee Department of Environment and Conservation, and the University of Tennessee organizes emerald ash borer trapping activities each year. These traps are large, purple triangular traps that resemble a box kite and are hung in ash trees throughout Tennessee. In 2014, 1,224 purple traps were placed across the state of Tennessee.
Keep ash trees healthy by watering, mulching, pruning, and protecting. Pesticides are available to help combat the emerald ash borer but are not 100% effective yet. Research is ongoing to develop pesticides and other management options to control the emerald ash borer. Avoid “knee jerk” reactions such as harvesting uninfested ash trees.
Contact a professional forester or your local TDF office for more information on ash and EAB management. Management decisions should consider: your current forest management objectives, the amount of ash in your forest, current ash markets, and your proximity to a known EAB infestation.
Managing EAB: Decision Guide (Purdue University)
Ash Management Guidelines for Private Forest Landowners (University of Minnesota Extension/MN DNR)
Insecticide Options for Protecting Ash Trees from EAB (North Central IPM Center)
What Can You Do?
Don’t Move Firewood! Firewood is a very likely transportation method for the emerald ash borer. The beetle is also known to travel in unprocessed ash logs, ash nursery stock, and other ash commodities as. It is very important to know where the emerald ash borer quarantines are if you are traveling between infested states or between counties that are known to be infested.
Learn to recognize what the signs and symptoms are of an infestation. Learn what the emerald ash borer looks like in its various growth stages and immediately contact your county agent, professional forester, or the Division of Forestry at 615.837.5432 if you suspect your ash tree is infected.