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Emerald ash borer: A Potential Threat to Mississippi Forests and Communities

The Emerald ash borer (EAB) Agrilus plannipenis Fairmaire) is an invasive insect, introduced to the United States from Eastern Asia.

It is a beetle from a group commonly referred to as metallic woodboring beetle. It was first found in the United States in the Detroit, Mich., area in 2002.

Since that time, it has spread to 15 states and parts of Canada, killing over 100 million ash trees in forests and communities. It has been found as far south as southern Missiouri.

The potential threat this insect poses to Mississippi is significant. According to the Mississippi Institute for Forest Inventory, there are nearly 200 million ash trees in Mississippi forests. This translates to approximately 1 percent of forests outside of the Delta and 5 percent within the Delta.

This may not sound like many trees, but ash makes up 5 percent of the value harvested in non-Delta forests, and 20 percent of the harvest value in the Delta.

The good news is that the EAB only attacks ash trees. The bad news is that all true ash trees are susceptible, and infestations are almost always fatal.

The color along the thorax and abdomen changes from red to orange as you move from the head to the tail.

EAB larvae are about 1.25 inches long, and are made up of many bell-shaped segments.

Adults emerge from under the bark of infested trees in the spring, and after mating, the females lay eggs on the bark of ash trees. Within a couple of weeks the young larvae burrow through the bark and into the phloem of the tree.

Under normal conditions, it takes about a year for the EAB to complete its lifecycle and re-emerge as adults.

The emerging adults leave very characteristic D-shaped exit holes. These holes are very small, about 0.125 inch in diameter. Other signs of infestation include crown dieback, and sprouting from the roots and base of tree.

Numerous other native insects cause similar kinds of damage to ash trees, including many species of similarly colored and shaped metallic woodboring beetles.

Clearwing borers are common ash pests in Mississippi along with the round head ash borers. Clearwing borers produce 0.25-inch diameter round exit holes and the round headed borers produce 0.25-inch oval exit holes that are not easily confused with D-shaped EAB exit holes.

Another native insect that has caused some confusion in southern states in recent years is the metallic woodboring beetle called Chrysobothris chrysoela. It is in the same family as the EAB, and as such makes similar, although larger, D-shaped exit holes. This insect is shorter and fatter than the EAB, and is a metallic purple color with metallic bronze to greenish spots.

Because of these similar native species, don’t lose hope if you encounter signs of woodboring activity in your ash trees. Contact your local county Extension office for help identifying the problem.

It’s probably only a matter of time before the EAB is found in Mississippi. The most important thing we can do to keep it out of Mississippi is to stop moving firewood across state lines. Firewood movement is the main way the EAB is spreading.

Research has shown that EAB larvae can persist in cut and split firewood pieces for at least two years.

As the fall hunting and camping season heats up, we need to be careful about the firewood we use. Ideally, we should only use firewood that’s found on site or from a source that you know is local. What you shouldn’t do is take firewood with your, or bring it back with you. There are insects and diseases from Mississippi that you might take with you to other states.

Buying firewood from local stores is no guarantee that it’s from a local source. The United States imports millions of dollars of firewood a year from other countries, and firewood is moved all around the country. For example, firewood sold at a store in Starkville, Miss., comes from Georgia.

Bagged wood like we find at our local stores is not necessarily insect or disease free.

Once we have the EAB, what can we do about it? It has no natural enemies here that we know of, and all of our true ash species are susceptible to it. There are some systemic insecticides, that if applied at the right times, can keep our trees EAB free. These insecticides work best if there is at least 50 percent of live crown left in tree. However, these insecticides can be costly, and would only be viable on trees in our yards and communities.

In the event of an outbreak, the Mississippi Department of Agriculture and Commerce will develop guidelines for the treatment and disposal of infested trees. In other states, this includes removal of the tree, followed by chipping the tree to a maximum size of 1-square inch pieces. These chips are usually then buried or burned.

In addition, most counties with EAB infestations have quarantines limiting the movement of firewood and ash nursery stock into and out of the county.

The EAB poses a serious potential threat to ash trees in Mississippi’s forests and communities. We need to implement prevention measures now, to help keep our forests safe.

The main thing we can do is to not move firewood. If you go camping, hunting, or fishing out of state, use firewood that you find there. Don’t take it with you, and don’t bring it back.

TAGS: Management
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