Just as the insects and trees become more active with the warming weather, so does the Arrest the Pest Hotline as people spend more time outdoors and take more notice of those insects and trees. The most common subject of calls to the hotline is suspect emerald ash borer (EAB) sightings. To help differentiate all the insects that might be mistaken for EAB, here are some tips for discriminating EAB from the rest:
1) You will probably not find an adult emerald ash borer. Although it has happened, it is unlikely that the first detection of EAB in an area will be through the discovery of an adult beetle. If you or someone you know believes they have found an adult EAB, look closely at possible look-alikes (below). The sixspotted tiger beetle is the insect most commonly mistaken for EAB in Minnesota.
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| Insects in Minnesota confused with EAB |
2) You will probably not find an EAB exit hole as the first sign of EAB in an area. EAB exit holes are almost as hard to find as the adult beetles in the early stages of an infestation. While it is true that EAB exit holes have a very distinctive shape (a 1/8" wide "D"-shaped hole in an ash tree), it can be easy to confuse other insect exit holes with it. Don't waste your time trying to find exit holes on a tree you suspect is infested with EAB.
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| Wood pecking on an ash tree |
3) Woodpecking on an ash tree is an excellent indicator that insects are present in a tree (right). However, other insects besides EAB can be found in ash trees and will be eaten by woodpeckers just as readily as EAB. So, woodpecking on an ash tree is not by itself diagnostic for EAB but is a good indicator that a closer look at the tree may be needed.
4) Woodpecking in a healthy looking ash tree or branch is more suspicious for EAB than woodpecking in a declining tree or branch. Other ash borers in Minnesota go after declining trees; emerald ash borer is the only one that attacks healthy ash trees.
5) Canopy decline and epicormic sprouts are not, by themselves, great indicators for EAB. These symptoms can have a wide range of causes. Also, in our experience in Minnesota any trees showing these symptoms due to EAB have also had evident woodpecking. Moreover, many EAB-infested trees that have been identified have had evident woodpecking, but not canopy decline or epicormic sprouting.
6) EAB tends to affect clumps of trees. If just one tree is showing signs of decline and woodpecking, but all other trees around it look ok - it is probably not EAB.
7) Bark cracks may be a good indicator for EAB on smaller trees. We have noticed that smaller trees (< 6" dbh) infested with EAB seem to be less likely than bigger trees to be woodpecked. For these trees, loose, cracking bark may be an indicator of EAB. Loose, cracking bark may also be found on larger trees, but may be less evident than woodpecking.
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| S-shaped gallery |
8) Look for "S"-shaped galleries beneath the bark at a woodpeck or bark crack in order to diagnose EAB in a tree. The shape of EAB galleries is very distinctive and can be differentiated from all other insect tunnels in ash by their sinuous shape. If you can't clearly see the letter "S" in the gallery, it is not EAB. For more help with identification of larval galleries check out MDA's guide.
9) EAB larvae can be discriminated from other insect larvae found in ash trees by the presence of urogomphi, which are small poker-like appendages at the tail end of the body.
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| Urogamphi on EAB, circled in red |
10) Remember, only MDA staff can confirm the presence of EAB in new areas. Use these tips to evaluate suspected EAB sightings and report any that seem legitimate to the Arrest the Pest Hotline at 888-545-6684 or Arrest.The.Pest@state.mn.us .
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