Thank you for your response to my earlier question. I didn’t explain my problem very well.
I have a river birch with a dead circle of grass at the tips of the branches. As the tree grows this circle gets bigger. Why is this happening? My tree is approximately 35 feet tall. The dead ring at the drip line is about 12″ wide. The grass from this circle to the trunk of the tree is fine.
The Gardener’s Answer
Hello again, Judy: I misunderstood your question and I have to admit that I have never seen or heard of this happening so I do not have a definitive answer for you, but here are some thoughts. River birch can sometimes become infected by small soft-bodied insects known as aphids. These rice-sized insects like to feed on foliage, especially new growth. As they use their piercing-sucking mouth parts to drink sap they secrete a sticky substance known as honeydew. It is possible that this honeydew and secondary forming black sooty mold are dripping from the tree to the grass below, only coming into contact with the grass directly below the drip line of the tree, killing the grass. For a positive diagnosis you should take a sample of new growth foliage and the dead grass to your horticulture agent at your County Cooperative Extension office. If you cannot reach a sample of the new growth you can have a certified arborist come out and take a look. They will be able to tell you if there is insect damage on the foliage. The Extension service should be able to put you in contact with a certified arborist in your area. You can find more information about the Meade County offices at www.ca.uky.edu/county.