Thursday, August 6, 2009


QUESTION: The leaves and limbs of my crape myrtle have black, grimy 'something' on them. What is it and what can I do to get rid of it?
ANSWER: Your crape myrtle has sooty mold. Small amounts of sooty mold will usually do little harm except for being unattractive. Large amounts could possibly reduce photosynthesis which could slow down plant growth. A mild insecticidal soap will aid in removing the sooty mold. However, the important thing is to eliminate the underlying cause of the sooty mold. Sooty mold occurs when piercing, sucking insects such as aphids, lace bugs, or scales leave behind honeydew on the plant on which then the sooty mold grows. Follow these links to read about ways to get rid of these insects: and

QUESTION: Caterpillars of various types are eating the leaves on my oak and river birch trees. What can I do to get rid of them?
ANSWER: One type of caterpillar we are seeing now is the yellow-necked caterpillar that does feed on oak leaves. The sawfly larvae which looks like a caterpillar often attacks the river birch. The damage done on large trees this late in the year is likely to be minimal and spraying is difficult. Only small trees with heavy damage should be treated. Often the caterpillars and the sawfly larvae can be handpicked and dropped in a bucket of soapy water. More detailed information can be found at these sites: and

QUESTION: My euonymus shrub's leaves have yellowish spots on them. What is causing it and can I fix it?
ANSWER: Euonymus scale is a common insect problem for this shrub. The yellow splotches on top of the leaf indicate a scale feeding underneath. Go to for details about control.