QuestionI have several young dogwood trees that have bore worms that were planted in our yard approximately 7 months to 1 year ago. Two have already died and we have removed the areas that look infected from the remaining trees. Is there any hope of saving these remaining trees through the use of a pesticide or other chemical treatment? And what is the risk that they would return and spread to other surrounding trees?
Answer A soil applied insecticide 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. 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. If you have not done so I would mulch around the trees with not more than 3 inches deep of organic mulch not piled up on the trunk. This will help hold moisture around the roots. During dry periods I would water with 1 inch of water--place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop. Do this once a week unless it rains.
As far as spread to adjacent trees borers usually need the tree to either have a wound that they can enter or the tree be under stress. Keeping the mower and string edgers away from the trunk and keeping the tree healthy will prevent borers from bothering a tree.
