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Boxwood psyllid and boxwood leafminer: what the extension services record

What Penn State Extension, NC State Extension, Missouri Botanical Garden and UC IPM say about the two common insects of boxwood: the psyllid that cups new leaves and the leafminer that blisters them from inside, with their life cycles and the damage described.

Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.

This page describes what the named sources say. It is not a diagnosis of any plant and does not say what should be done with one. Boxwood is a shrub, so this page sits beside the tree pests only because tree crews and nurseries meet both insects on it. None of the five pages read lists either insect as regulated or notifiable. Each section names its source, all read on October 9, 2026. Both insects have rows in insect pests of trees. A third boxwood pest with a regulated status has its own page: box tree moth.

The two insects side by side

PointBoxwood psyllidBoxwood leafminer
Scientific namePenn State prints Cacopsylla busi, NC State Cacopsylla buxi, Missouri Botanical Garden Psylla buxi.Monarthropalpus flavus (Penn State, UC IPM).
What it isA small green sucking insect that resembles a leafhopper or a miniature cicada (NC State, Missouri Botanical Garden).A gall midge, a mosquito-like fly whose larvae mine inside the leaf (UC IPM).
Overwinters asEggs between the bud scales (Penn State, Missouri Botanical Garden). NC State says first instar nymphs inside orange egg shells.A larva inside the leaf blister (Penn State, UC IPM).
GenerationsOne a year (Penn State, NC State, Missouri Botanical Garden).One a year (Penn State, UC IPM).
Adult sizeAbout 3 mm (Penn State); up to 1/8 inch (NC State); 1/16 inch (Missouri Botanical Garden).2.5 mm (Penn State, UC IPM).
DamageCupped, curled terminal leaves, with white waxy secretions around the nymphs.Blisters on the underside of leaves, yellowing, early leaf drop and sometimes dead twigs.

Boxwood psyllid

Penn State describes the eggs as small, orange and spindle-shaped, and the nymphs as covered with a white waxy secretion that readily tells them from other boxwood insects. The adults are light green. All three pages place the egg hatch at the start of spring bud opening; Missouri Botanical Garden gives April to May for new growth, and Penn State has nymphs mature by early June. NC State says adults emerge in late May and June and females lay one to seven eggs under each bud scale in July or August; Missouri Botanical Garden says the eggs are laid in June and July. Penn State says nymphs feed on tender foliage and several can be enclosed in one pocket of cupped leaves, and that the injury is very noticeable.

On hosts, NC State says boxwood is the only known host, both American and English varieties are attacked and American boxwoods are more likely to be severely infested. Missouri Botanical Garden calls the psyllid the most common insect pest of Buxus sempervirens while saying all boxwoods are susceptible. NC State and Missouri Botanical Garden both say it occurs wherever boxwood grows, most often in temperate parts of the United States. Penn State calls it common but not considered as destructive as other boxwood pests. Missouri Botanical Garden says the leaves usually fall after about one year and terminal growth is affected for about two, while NC State says plants sometimes outgrow the injury by midsummer, and Missouri Botanical Garden calls the damage only aesthetic and rarely a threat to the long-term health of the plant.

Boxwood leafminer

Penn State says the leafminer was first reported in the United States as a pest in 1910 and is found across the country wherever boxwood grows, and calls it a serious pest of Pennsylvania boxwood plantings. It describes the eggs as white to transparent, the larvae as whitish to lemon-yellow maggots 3 mm long, and the adults as yellow to orange-red gnat-like flies. UC IPM gives adults about 1/10 inch long with long antennae and legs and visible around boxwoods for about two weeks in spring.

The life cycle runs through the leaf. Penn State says the larva overwinters in the blister, the blister develops a translucent window in spring, the pupa pushes through the lower leaf surface in May and the adults emerge, mate shortly after emerging, and the female lays an average of 29 eggs in new foliage with a needle-like ovipositor. UC IPM says females lay up to about 20 eggs per leaf in April, eggs hatch in two to three weeks, the larvae pass through three instars and their mines merge as they feed in groups through the summer. Penn State gives 14 to 21 days to hatch and says the larvae feed in the leaf through the remainder of the summer.

On damage, Penn State says the larvae feed between the upper and lower leaf surfaces, producing a blister that may or may not discolor, that a heavily infested leaf can swell all over, and that infested leaflets drop early, leaving ragged plants with occasional dead twigs. It says most varieties of boxwood are attacked. UC IPM describes pale green or yellow spots on the upper surface, brownish to green swollen blisters beneath, infested leaves smaller and more yellow, and under heavy infestation leaves turning brown and dropping, branch dieback and plants more open to stress and disease. UC IPM also lists boxwood selections it calls resistant to the leafminer, among them Buxus sempervirens cultivars such as Suffruticosa and Pendula.

Status and sources of information

None of the pages names a quarantine, an order or a report line. This page gives no treatment steps, product names, rates or timings. For who may apply pesticides see pesticide licences.

Sources