Scale – On Boxwood
Q: Down deep on my boxwood stems I have found white-looking things that are very rounded in shape. When I pull them off their underside is blood red. I can squash them between my fingers and they crunch a bit. These things look like scale but are white and have no fuzz around them. I don’t like spraying insecticides but since these are the grandparent plants for the boxwood at the Garden Club of Georgia Headquarters in Athens, I feel a real sense of responsibility to take care of them properly.
A: I’ll bet you have wax scale. Folks see them commonly after pruning their holly but they infest other plants, including boxwood. As with all scale insects, the adults you’ve noticed protect themselves with a waxy outer coating as they suck plant sap. Their red eggs are deposited under the wax coat. If you can physically remove all of the adults, that’s a good first step. Young wax scale, though, are camouflaged on plant stems. At this time even the old standby horticultural oil will not suffocate many of them because they are not active in cold weather. Even so, a thorough spray with the oil now on a warm afternoon may kill some percentage of the insects.
The key to scale control is timing your spray to kill the crawlers just after they hatch from the eggs in April. Use carbaryl (click for sources) three times, at two-week intervals, starting in mid-April to control the baby scale as they emerge from under the adults.