I talked about this at about the same time last year but the problem has not gone away. The scale problem on hollies has only gotten worse when gone untreated. After a consult yesterday with Dr. Lee Townsend it turns out we are fighting Cottony Camelia Scale. Cottony camellia scale is a sap-feeding insect that infests camellia, holly, yew, euonymus and maple. Infested plants usually have a significant amount of black sooty mold growing on the sugary “honeydew” or liquid waste produced by the insects. Heavy infestations may cause the leaves to turn light green in the spring. The easily overlooked flat females, living on the underside of leaves, are about 1/8 inch long, oval and yellowish tan with a brown margin. However, they produce very noticeable elongate white cottony sacs containing several hundred eggs. Management alternatives:
Light infestations often can be managed by hand-picking and destroying infested leaves. Remove any cottony egg masses found on leaves in mid- to late May.
Prune and destroy more heavily infested leaves and branches when practical.
Crawlers hatch from these eggs from late May through June. They settle on the undersides of the leaves to feed on sap and grow through winter. This is the stage that is most vulnerable to control with insecticides or insecticidal soap. Treatment should be made in late June. Use of insecticidal soap helps to preserve natural enemies of the scale.
Use a superior dormant oil spray during the winter to kill overwintering scales on the foliage.
