Psylla buxi

Boxwood psyllid cupping damage to boxwood leaves. Photo: Tawny Simisky
Scientific Name: Psylla buxi
Common Name: Boxwood Psyllid
Growing Degree Days (GDD's): 290–440 GDD's, Base 50F, March 1st Start Date. (Source: Cornell Cooperative Extension)
Host Plant(s) Common Name (Scientific Name)
American boxwood (Buxus sempervirens) *More likely to be severely attacked.
English boxwood (Buxus sempervirens 'Suffruticosa') *Not as severely attacked by the psyllid.
Insect Description:

This insect is common to the temperate United States. Eggs are inserted between bud scales by adult females early in the summer. Eggs are orange and spindle-shaped and often only the tips of the egg can be viewed beyond the edge of the bud scale. Nymphs develop and overwinter within the eggshell (Johnson and Lyon, 1991). As soon as buds expand, nymphs emerge and begin feeding. As the leaf curls and cups due to feeding, multiple nymphs may become protected within a pocket of leaves. Nymphs mature and secrete a white, waxy wool coating. Nymphs mature into adults and are green, winged, and sometimes referred to as plant lice. There is one generation per year.
Damage to Host:

Foliage of boxwood. Feeds on developing buds and leaves, causing upward cupping and yellowing. English boxwood is somewhat resistant to this pest. Symptoms on leaves can remain for a few years, even if damaging populations of this insect have gone. Occasionally, adults may bite people but bites are not serious. Boxwood psyllid damage to its namesake host is typically thought to be aesthetic in nature, and not requiring chemical management intervention. Some plants may even refoliate in the same season, as boxwood psyllid causes its damage early in the spring. 
Monitoring:

Symptomatic plants may be treated with a dormant oil application on the eggs (nymphs inside) in the spring. Monitor for early nymph emergence and manage before they become protected by cupped leaves. In June, shaken plants might expose flying adults.
Cultural Management:

Plant English boxwood where this pest is known to be problematic and cupping leaves cannot be tolerated. English boxwood is also thought to be resistant to the more serious pest, the boxwood leafminer. (Plan management for the boxwood psyllid with the boxwood leafminer also in mind.)

Partial resistance to the boxwood psyllid is reported by Cornell Cooperative Extension in the following: B. x ‘Glencoe’ (‘Chicagoland Green’), B. microphylla ‘Fiorii’, B. sempervirens ‘Arborescens’, and hybrids 'Green Mountain’ and ‘Green Velvet’.
Natural Enemies & Biological Control:

None reported at this time.
Chemical Management:

Acetamiprid (L)

Azadirachtin (NL)

Beauveria bassiana (NL)

Carbaryl (NL)

Chlorpyrifos (N)

Cyantraniliprole (NL)

Dinotefuran (NL)

Flonicamid+cyclaniliprole (N)

Horticultural oil (eggs) (L)

Imidacloprid (L)

Insecticidal soap (NL)

Isaria (paecilomyces) fumosoroseus (NL)

Neem oil (NL)

Pyrethrin+sulfur (NL)

Tau-fluvalinate (NL)
Notes:

Active ingredients that may be applied systemically include: acetamiprid (injection), azadirachtin (injection, soil drench), cyantraniliprole (soil drench, injection), dinotefuran (soil drench), imidacloprid (soil drench), and neem oil (soil drench).

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022 neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: September 27, 2024. To check current product registrations in Massachusetts, please visit the MA Department of Agricultural Resources Pesticide Product Registration page and click on "Search Pesticide Products Registered in Massachusetts - Kelly Solutions".