I have two large American Hollies on either side of my house. The trees have...
I have two large American Hollies on either side of my house. The trees have developed a black, sooty substance on the back of the leaves and on the trunk. The trees have lost many leaves and look sick. Years ago, in Montgomery County, Md the same thing occurred and the trees were sprayed with a dormant oil and I don't know what it was. Can you help?
Your hollies have scale, a type of insect which is on the underside of the leaves. Probably cottony camellia scale. This scale excretes honeydew, which is sugary and lands on the leaves and branches below it. A black fungus known as sooty mold grows in the honeydew and makes your holly appear black.
You need to treat your trees immediately for cottony camellia scale or this sucking insect will suck the life out of your trees. Put "cottony camellia scale" into the search box on our website and follow the instructions. Spraying needs to be done with different products at different times of the year.