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Published June 03, 2009, 12:00 AM

A mean, green insect to watch

This week I have been fielding many calls regarding emerald ash borers (EABs), so I will start my column by updating you on this devastating pest.

By: By Robin Trott, Extension Educator, Alexandria Echo Press

This week I have been fielding many calls regarding emerald ash borers (EABs), so I will start my column by updating you on this devastating pest. On May 14, EABs were found in a neighborhood in St. Paul. Since then, gardeners statewide are on the lookout for this mean, green insect.

EAB is a native of Asia and was first discovered in Michigan in 2002. Since that time it has spread to nine other eastern states and two Canadian provinces. Larvae of the one-third inch to one-half inch long beetle tunnel beneath the bark of the tree until they have completely girdled the trunk. This destructive insect is responsible for killing millions of trees in the affected areas. Since Minnesota has the second largest population of ash trees in the United States (second only to Maine) the presence of this pest could significantly affect our urban and rural landscape.

There are many green garden insects, so how do you know if you’ve found EABs? Look for a small beetle that ranges from iridescent green to copper-green in color. It’s widest behind the head, and its abdomen tapers to a point. The body beneath the wings is a reddish-purple color. If you don’t see insects, but notice your ash tree beginning to wilt from the top, look at the bark. EABs leave small “D” shaped exit holes in the trunk of trees. If you lift the bark, you will find “S” shaped larval trails.

Trees infested with EABs do not die immediately; it may take two to four years for infected trees to succumb to the infestation. Although insecticides can effectively protect trees from this pest, trees further than 10 to 15 miles from a known infestation are considered low risk, and do not need to be treated.

The good news is that there is a team of volunteers trained to be EAB first detectors. They are on the lookout for the spread of this bug, and can help homeowners identify an infestation. In the meantime, you can help to prevent the spread of EAB:

1. Do not transport firewood within Minnesota. On its own, EAB will usually move only about one-half mile a year. With help from people, it can travel hundreds of miles carried in firewood, wood products and nursery stock.

2. Visually inspect your trees; early detection is the key.

3. Spread the word to friends, neighbors and co-workers.

If you want more information about the emerald ash borer, you can check out our webpage at www.extension.umn.edu, click on ash borer. I will keep you apprised of any updates as they become available.

Finally, I would like to introduce myself. I am the new horticulture educator for Douglas County and will be visiting with you through this column each week. I welcome your questions and suggestions. Please contact me at the Extension office at (320) 762-3890, or via e-mail at master.gardener@mail.co.douglas.mn.us. It is my hope that, together, we can address the gardening concerns that regularly challenge all of us.

Until next time, happy gardening!

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