Euonymus scale is a very common and very destructive insect to the euonymus. They are hard to detect because they usually start under the leaves. It is only after they have caused serious damage to the plant are they noticed.
The symptoms of the scale invasion are yellow or whitish spots that appear on the upper surface of the leaves. This is the result of the scale on the lower surface sucking nutrients out of the leaf. By mid to late summer many of the leaves will have fallen off the shrub and sections of it may have died. The infestation may be so severe that it is often mistaken for a disease such as powdery mildew. The narrow white scales are the males, and the brown oyster shell shaped bumps are the females.
At this time of the year an application of horticultural oil is about all that can be done. The best time to eradicate them is late spring to early summer when the young scales (called crawlers) are active. Two sprays should be applied, one in early June and one in mid July. Use organic horticultural oil at that time.
If scales are persistent, please stop in to see us for further recommendations.
Euonymus Scale: "Dr. Z's" Tip of the Week
This entry was posted on September 16, 2015.