Question

sunset maple   QUESTION: 9 year old sunset maple trees at sidewalk in 5 ft wide space between walkway and street. Bark splitting and peeling back. Removal of diseased bark seems to show round symetrical borer holes. No limb or leaf damage as yet. spraying with a pruning type paint shows the holes more clearly. one photo shows non trimmed trunk on neighbor tree.

ANSWER: This sounds like an insect called a borer. The bark is a result of the feeding of the insect. I would not use the pruning paint--this will slow down the haling process. Just cut the loose bark off and treat the are with an insecticide. A good  spray for borers is one called Merit or Onyx. These are sprayed on the trunk and are absorbed into the wood killing the borer. A soil applied insecticide that should work is Bayer Advanced Tree and Shrub Insect control. This is applied to the soil and the roots transport it into the trees system killing any insect attacking the tree. It is good for large trees where you can not reach the trunk. This product takes longer to get into the system and is a little more expensive but will last longer than the spray. Both will do the same thing as far as killing the insect. Here is a web link to this product--Check with your local nursery for these products. http://www.bayeradvanced.com/product/Tree-Shrub-Insect-Control/concentrate.html
Usually borers attack trees under stress so I would recommend that you fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. This will increase the health of the tree.


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QUESTION: Merit contains Imidichcloprid as does Bayer insect systemic product. Couldn't you use same thing both as spray and systemic treatment? GLoewe

Answer
The first thing to remember regarding borer control is that borers tend to attack trees under stress. The best borer control is a healthy, vigorous tree. This means watering during dry periods and mulching under the tree to reduce competition from other plants and provide a more root-friendly environment. As a preventive you should fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. Do this this Fall and again in the spring.
You could but the systemic action will penetrate the bark and woody cells better and reach the insect in the wood. There are other insecticides that will kill the borer insect before or as it enters the bark but once it is under the bark the systemic insecticide works much better.

Permethrin: Permethrin is found in Bonide Eight, Spectracide Bug Stop Multipurpose Insect Control, Fertilome Indoor/Outdoor Insect Spray and Fertilome Kill-A-Bug II is labeled only for Peach Twig Borer and Lesser Peachtree Borer. Fortunately, permethrin is also found in Hi-Yield Lawn, Garden, Pet and Livestock Insect Control and the commercial product Astro. Both of these products have a wide borer label including both roundheaded and flatheaded borers. Note that the Hi-Yield product has a virtually identical product called Garden, Pet and Livestock Insect Control that does not have a wide borer label. The easy way to tell the two apart is packaging. The latter product comes in an 8-ounce bottle and the other (the one you want) in a 32-ounce container. Permethrin is not systemic and works by killing the young borer larva as it hatches from the egg and tries to bore into the bark. Therefore, the product must be present on the bark before the eggs hatch. Keeping the product on the trunk for some of these borers can be a real challenge. For example, trees attacked by the flatheaded apple tree borer would need protection from May through August. The label recommends reapplication on a monthly interval. Again, the best borer control is a healthy, vigorous tree.

Of course you could dig the borer larvae out with a knife and kill it this way but I still think for the long run the Merit or the Bayer product is best.