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Emerald ash borer found here

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By Dennis Morgeson

Well, we knew for several years it was going to eventually make it to Kentucky and now it has!  The emerald ash borer has been found for the first time in Kentucky in a wood lot in Shelby County and a residential landscape in Jessamine County.  This has been confirmed by the state entomologist. This insect when it becomes widespread is going to kill most of our ash trees of all cultivars.  Ash is a very important tree in Kentucky because of its uses including shade, shelter, furniture, and presence in yards and woodlands.  Also, it is used to make the Louisville Slugger baseball bat! I am afraid that the ash tree is going to become like elm and chestnut trees which have been devastated by diseases brought in from other countries.  This time it’s an insect however.  Borers are extremely hard to control and they have a high chance of killing trees because of their tunneling and feeding which girdles trees.

The emerald ash borer 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. It was first detected in July 2002 in southeastern Michigan and has since been found in Ohio, Illinois, Indiana, Maryland, Missouri, Pennsylvania, West Virginia, Wisconsin, Virginia, Ontario, and Quebec.

The emerald ash borer poses an enormous threat to urban and rural forests, because unlike many wood inhabiting insects, emerald ash borer targets and kills healthy ash trees.

The emerald ash borer is a small, metallic, emerald green beetle about a half inch in length and one eighth inch wide. The adults leave a D-shaped hole in the bark when they emerge in the spring. The beetles may be seen resting on ash leaves or chewing small feeding notches in the edges of ash leaves. The adult female beetle lays eggs in bark crevices of ash trees specifically. 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 segmented. Older larvae can grow up to an inch in length. The tunneling activity eventually kills the tree in two to three years.

There are a lot of green insects that can be confused with the emerald ash borer. 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 Emerald ash borer can be found at the University of Kentucky Extension Entomology website http://pest.ca.uky.edu/EXT/EAB/welcome.html.

Visible symptoms of potentially infested ash trees are a die-back in the top one-third of the canopy which continues to die until the tree is bare. Shoots and sprouts from the roots and trunk also occur. The bark may be splitting or sloughing on the tree. Woodpecker damage on the trunk and main limbs may be apparent. Under the bark, serpentine galleries are present and one-eighth inch diameter, D-shaped exit holes will be seen in the bark.

There are native ash tree borers in Kentucky that can also damage ash trees. The emerald ash borer beetle or larva needs to be found before the presence of the insect can be confirmed.

Officials urge Kentuckians to take several steps to help keep the emerald ash borer from spreading. These actions include don’t transport firewood, even within Kentucky. Don’t bring firewood along on a camping trip. Buy the wood you need locally. Don’t bring the extra wood home with you. In addition, don’t buy or move firewood from outside Kentucky. If someone comes to your door selling firewood, ask them about the source of the wood. If it came from outside Kentucky, don’t buy it.

What else can we do? At this time we should identify ash trees in the landscape and observe them. Ash trees have branches that grow opposite each other. The leaves are compound which means 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 that are attached opposite to each other on the petiole. Help to identify an ash tree is available for you at the Washington County Cooperative Extension Service office.

The economics of treating ash trees with insecticides for emerald ash borer protection are complicated. Factors that need to be considered include the cost of the insecticide, expense of applying the insecticide, the size of the tree, and the likelihood of success. Trees will need to be treated annually. In many cases, it may be more cost-effective to remove and replace the ash tree.

Wait until the emerald ash borer has been found in the area. Preventative treatment with insecticides is not recommended at this point until the insect has been found, because there is not a benefit to the treatment.

When the insect is found, there may be chemical alternatives to use. At that point, decisions will need to be made as to the amount of money that a person wants to spend on the insecticide treatment.

Keep the ash tree healthy and minimize stress on them by avoiding mechanical damage to the tree by lawn mowers or string trimmers. In addition, do not add soil over the roots in order to start a flower garden. Provide water for the tree during very dry periods.

When you are thinking about planting trees in the landscape, select species other than ash (Fraxinus spp.).

If you suspect an ash tree has been affected by the emerald ash borer, contact me at the Washington County Extension Office at 859-336-7741.

Question and Answer:

Where can I find more information on the emerald ash borer? Information is available at the Washington County Cooperative Extension Service office and through the wWeb sites of: http://pest.ca.uky.edu/EXT/EAB/welcome.html , http://www.emeraldashborer.info/ and http://www.entm.purdue.edu/EAB/.

Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability, or national origin.