|MY MAPLE TREES ARE INFECTED BY SOME TYPE OF TREE BORERS. I HAVE SPRAYED WITH RECCOMENDED PESTICIDE. HOWEVER, THEY HAVE GOTTEN UNDER THE BARK ON ONE AND THE BARK IS LOOSENING AND EXPOSING THE TRUNK. WHAT CAN I SPRAY ON THE BARE TRUNK TO PROTECT THE TREE?|
|Borers within trees cannot be successfully treated with insecticides because the insects are in a protected site. insecticidal control is best achieved if sprays are made during periods of adult activity and egg laying.
Trunk sprays can kill the adult borers during egg laying and also may be effective against newly emerged larvae before they enter the trunk. Canopy spraying also may increase control of longhorned beetles and metallic wood borers. Adults often feed on twigs and foliage before laying eggs.
Timing of trunk sprays varies with different borer species so it's important to have the larvae or adults identified by your local cooperative extension office. The most common treatment for borers is the insecticide permethrin. April through June is the most common time for treatment.
Since damage has already been done to the tree, there's nothing you can do to repair the damage. The exposed wood is already dead so the tree has sealed it up from the inside. Just leave the damaged area alone and eventually the healthy bark will callous over it. Best wishes with your maple.