Hello, I called your office yesterday about a problem with my tall holly...
Hello, I called your office yesterday about a problem with my tall holly trees and what the person on the phone suggested the problem might be is exactly correct! It is cottony camellia scale. There are small white residues of where the insects lived under the leaves and the top of the leaves are covered in soot like black substance. Is this harmful to the trees? Should I (must I) spray?Can this spread to other trees around the holly? thanks
Cottony camellia scales are sucking insects. They sip plant sap and then excrete a sticky 'honeydew', which drips on leaves, and then secondarily the black sooty mold grows on that.
The combination of sucking and covering the leaves (which can lesson photosynthesis) can weaken the plant, but dieback is not common.
If most of the plant is affected, we suggest that during the dormant season, (after the leaves of all the deciduous trees nearby have fallen) spray the tree with a horticultural oil at a dormant rate.
There is one generation per year and immatures overwinter on bark or leaves. Covering them with a oil will help control the infestation while not harming beneficial insects.