For much of the U.S., boxwood leafminer (Monarthropalpus flavus) is the most prevalent and destructive pest of boxwood. So much so that one of the main criteria for selection of our NewGen® cultivars has been for superior resistance to boxwood leafminer.
But what are these white fluffy bits scattered amongst new growth? The culprit is Psylla buxi, the boxwood psyllid. Nymphs emerge in April to May across much of their range. The white filaments are secretions that can serve as “cover” for the larvae.
Those aren’t snowflakes! Note the fluffy white secretions from boxwood psyllid nymphs.
As a piercing and sucking pest, they’re after the sap from soft young foliage or unopened buds. The damage from feeding action can result in inwardly cupped foliage at the tips of the branches. The nymphs mature rapidly, with the adult resembling a little leafhopper or tiny cicada. Eggs are laid into bud scales to start the process over the next year.
Nymph photo (left) courtesy of Nancy Gregory, University of Delaware, Bugwood.org
Damage photo (right) courtesy of Penn State Department of Plant Pathology & Environmental Microbiology Archives , Penn State University, Bugwood.org
The good news? Damage, if visible, is only cosmetic. Several sources note American Boxwood (Buxus sempervirens, straight species) seem to be the most likely to show damage.
One option is to “let it be” as there are many natural predators that snack on psyllid. Another is to lightly shear off the boxwood tips in early spring, prior to larvae emergence. Insecticidal soaps or horticultural oils work if applied prior to spring flush. If just a few of the pests are visible, never underestimate the utility of a strong spray/stream of water directed at infested areas. If you’re already using a systemic for control of leafminer, psyllids probably aren’t an issue. Always consult your state or provincial authorities’ pest management guide or other regulatory agency for information on labeled chemicals for a specific pest.