The boxwood psyllid (Psylla buxi) is the most common insect pest of Buxus sempervirens but all boxwoods are susceptible. They are found most often in the temperate parts of the United States but occur wherever boxwoods are grown in this country. It causes damage by piercing and sucking sap from buds and young leaves resulting in a conspicuous cupping of the foliage. These leaves are weakened and will usually fall off after about one year. The terminal growth will be affected for about two years.

Symptoms and Diagnosis

The symptoms of a psyllid infestation are cupping of the young terminal leaves as they begin growth in spring. The psyllid nymphs will be visible inside the cupped leaves although the most obvious sign is the waxy filaments and secretions they produce.

Life Cycle

Boxwood psyllids have one generation per year. They overwinter as eggs in small orange spindle-shaped eggs that have been laid in between bud scales. Emerging as the new growth begins in April to May and feeding on the buds and young leaves, the nymphs are light green and may have dark markings. They produce and are partly covered with waxy filamentous secretions. The sucking damage causes the leaves to cup and creates a protected area for the developing nymphs. They mature into light green, 1/16 inch long adults that look like miniature cicadas in late May to early June. The adults lay eggs in the bud scales in June and July.

Integrated Pest Management Strategies

1.  If the infestation is small, do nothing. The damage caused by boxwood psyllids is only aesthetic and rarely affects the long-term health of the plant.

2.  Prune out and destroy the affected tips. If done before the nymphs mature into adults, this will decrease the number of eggs for next year. The damage caused by psyllids is complete by early summer and the shrub will outgrow the injury.

3.  Spray horticultural oil or insecticidal soap. Apply in early May when new growth occurs. Pesticides sprayed before or after that time will not be effective as the eggs are protected by the bud scales and the nymphs are protected by the cupped leaves.

4.  Chemical controls are also available, but should only be used when the infestation is severe. Several pesticides are labeled for use against boxwood psyllids. Always be careful to read the label directions fully before applying any pesticide, and follow directions completely. Systemic insecticides may be necessary during certain stages of the psyllid’s life cycle. Pesticides that are absorbed into the foliage, such as acephate, will control adults in June.

Organic Strategies

Strategies 1 and 2 are strictly organic approaches. For an organic approach to Strategies 3, consult the Organic Materials Review Institute (OMRI™) for appropriate insecticidal soap products.

Pesticide Disclaimer: 

Always follow the product's label and ensure the product is effective against boxwood psyllid. Not following the pesticide label before usage is a violation of federal law.