We have been waiting, but now it is time to take action. The emerald ash borer (EAB) was found on the east side of the county in 2020. This beetle attacks species of ash trees, but won’t bother your maples, oaks, etc. Unlike some borers that only attack trees under stress, this one also targets and kills healthy ash trees. If you have an ash tree in your landscape, it is time to make decisions of whether to remove the tree or treat the tree for this borer. A dead ash tree is brittle and dangerous.
The emerald ash borer was first discovered in eastern Michigan near Detroit in 2002. EAB is an invasive species of wood-boring beetle native to China and eastern Asia. It probably arrived in North America hidden in wood packing materials commonly used to ship consumer and other goods.
EAB was first detected in central Kentucky in 2009. It has been spread by humans through the movement of firewood and unprocessed ash logs. Adult EABs only fly about half a mile per day. The emerald ash borer had been found across the river in Indiana and is now in Daviess County.
Officials urge Kentuckians to prevent the spread by not transporting firewood outside or within Kentucky. Buy the wood you need locally, and leave any extra wood behind at the campsite.
At this time, determine if you have ash trees. To identify an ash tree, look for branches growing opposite each other. The leaves are compound, meaning there are several leaflets attached to a petiole. At the base of the petiole, you will find a bud. Buds will not be found at the base of the leaflets. The leaflets are attached opposite of each other on the petiole. The Cooperative Extension Service Office can help identify an ash tree. Photos and descriptions can be found at http://www.emeraldashborer.info/documents/E-2942.pdf.
The EAB adult is a small, metallic, emerald-green beetle about three-eighths to three-fourths inch in length and one-fifth inch wide. The adults leave a D-shaped hole in the bark when they emerge in early May to late June or beyond. There are native ash tree borers in Kentucky that can also damage ash trees, but they do not have the same shape of exit hole as the EAB.
The newly emerged adults are most active when it is warm and sunny. They may be seen resting on ash leaves or chewing irregular notches in the edges of ash leaves. They feed for several days before mating. The mated females will feed for another week or two before laying eggs in bark crevices of ash trees. The eggs hatch and the larvae bore into the ash tree under the bark where it feeds and grows. The larvae are creamy white in color, flattened, and arranged in triangular segments. Older larvae can grow up to an inch in length. The tunneling activity eventually kills the tree in two to three years.
Visible symptoms of potentially infested ash trees include a die-back in the top one-third of the canopy which continues to die until the tree is bare. Woodpecker damage on the trunk and main limbs may be apparent. Shoots and sprouts from the roots and trunk also occur and, at this point, it is probably too late to treat. You may also see the bark splitting or sloughing on the tree. Under the bark, serpentine galleries are present and one-eighth inch diameter, D-shaped exit holes will be seen in the bark. The University of Kentucky, Department of Entomology website http://ky-caps.ca.uky.edu/emerald-ash-borer shows photos of the insect and damage they cause.
To help decide what to do with your ash trees, consult “Managing Emerald Ash Borer: Decision Guide” from Purdue University at http://extension.entm.purdue.edu/EAB/pdf/NABB_DecisionGuide.pdf. Considerations include: How valuable is the tree to your landscape or to you? Is the ash tree healthy? The University of Kentucky recommends homeowners begin considering protective treatment, if wanted, when an EAB infestation is found in the county or within 15 miles of their location.
Homeowners can protect desirable ash trees with diameters of 20 inches or less at 4.5 feet above ground level (DBH) annually using a soil drench near the trunk containing the active ingredients dinotefuran or imidacloprid. The product is taken up systemically into the plant. Timing is important; most annual products are applied in mid- to late-spring but autumn applications are also on the label.
Certified tree care professionals are able to use products and techniques that can protect larger trees. Emamectin benzoate is one of the active ingredients recommended to be used as a trunk injection in mid- to late-spring. This product can be applied every two to three years.
For more information about the emerald ash borer, contact the Daviess County Cooperative Extension Service at 270-685-8480 or firstname.lastname@example.org.
Annette’s TipOther green insects that can be confused with the emerald ash borer (EAB). These include bark gnawing beetle (family Trogossitidae), Buprestis rufipes, green June beetle, caterpillar hunter, Japanese beetle, green tiger beetle, green stinkbug, dogbane beetle, and metallic bee. A picture of these insects and relative size compared to the EAB can be found at https://entomology.unl.edu/eablookalikes.pdf. If you need help identifying an insect, place it in white vinegar and take it to your county Cooperative Extension Service Office.
Annette Meyer Heisdorffer, PhD, is the horticulture extension agent with the Daviess County Extension Office. She can be reached by calling 270-685-8480.