by Lee Townsend, Extension Entomologist
University of Kentucky College of Agriculture
Boxwood psyllids are small insects that produce a distinctive cupping of leaves as the immature stages (nymphs) remove sap from tender expanding foliage. They feed only on boxwood; the damage is especially noticeable on American boxwood. These insects affect the appearance of the plant but are not a threat to plant health or vigor.
Fig 1 (left): Cupping of boxwood foliage due to psyllid feeding
Fig 2 (right): Boxwood psyllid nymph; a white waxy secretion produced
by the insect is visible along the edge of the abdomen.
Boxwood psyllids overwinter as eggs inserted between the bud scales. The eggs begin to hatch in the spring as soon as the buds begin to open and new leaves expand. Nymphs remain sheltered within the cupped leaves, becoming adults in late May and early June. The adults will feed but do not cause noticeable damage. After mating, females will lay eggs under bud scales where they will remain until spring. There is a one generation each year.
Do nothing- Psyllid damage is primarily aesthetic so light infestations will produce only scattered leaf cupping. Watch each spring because numbers can build over time.
Mechanical control- If practical, prune and destroy infested tips containing nymphs before mid-May when they become adults and lay eggs.
Insecticides – Low impact options include insecticidal soap or summer horticultural oil. They must be applied when new growth begins and require thorough spray coverage because they work by direct contact with the insects. There is no residual effect. Check several days after treatment to see if live nymphs are still present and treat again if necessary.
Residual insecticides – Products containing active ingredients such as acephate, cyfluthrin, cyhalothrin, permethrin malathion, or spinosad can be sprayed on the foliage in early to mid-May to control high infestations of nymphs. Spraying after the leaves have fully expanded (after mid-late May) won't affect current damage but may help to reduce psyllid injury the following year.
Systemic insecticides – products containing the active ingredients dinotefuran or imidacloprid may be applied to the soil around boxwoods according to label directions. The insecticide is taken up by the roots and distributed throughout the plant in the sap. The application must be made 2 to 4 weeks before the psyllids begin to feed. Watch for mite infestations when using these products.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!