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What Is Boxwood Leafminer?

April 08, 2023

Boxwood leafminer is a common pest that affects boxwood shrubs. These pests appear as tiny flies on the undersides of boxwood leaves and cause significant damage to boxwood shrubs by feeding on the leaf tissue. The species was first reported as a pest in the United States in 1910 and is now found across the United States wherever boxwood grows.

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Boxwood Leafminer Appearance

Adult boxwood leafminers are small, less than 1/16 inch long, have a yellowish-orange coloration, and are similar to gnat-like flies. These leafminers have two pairs of wings and six long, thin legs. The eggs are white to transparent and hatch into small whitish or lemon-yellow 3mm long larvae or maggots. These larvae initially lack any legs, but they gain legs as they age.

Boxwood Leafminer Life Stages

The life cycle of boxwood leafminer is broken down into four stages: egg, larva (or maggot), pupa, and adult.

  1. Egg: Females lay eggs on the undersides of leaves in summer. They hatch into larvae within about two days. On average, females lay around 29 eggs and die soon afterward. The eggs take anywhere from 14-21 days to hatch.
  2. Larvae: Larvae emerge from the eggs after hatching. Then the larvae feed on the leaves the remainder of summer through early fall. Larvae pupate in late winter.
  3. Pupa: Pupating is a stage when insects transition from larvae to adults. Eventually, the leafminers emerge in May.
  4. Adult: Adult leafminers mate soon after emerging and the females deposit their eggs in new foliage by thrusting a curved needle-like ovipositor through the lower surface of the leaf, and the cycle repeats.

Boxwood Leafminer Damage

The boxwood leafminer damages the leaves by laying eggs on them, which, as mentioned previously, hatch into larvae that feed on the leaves until maturing into adults. The laying of the eggs and the larvae feeding on the upper and lower leaf surfaces causes leaf blisters on the infested leaves. These blisters can become discolored and leaf drop may result.

Homeowners may see premature leaf drop (when green leaves turn brown before falling off), stunted growth, and yellow spots in some areas where leafminers have been feeding.

Managing & Controlling Boxwood Leafminer

To manage and control infestations, a plant health care professional needs to identify the presence of leafminers by examining a property. Once identified, our expert can prune and dispose of heavily infested branches to prevent the spread of the infestation.

square image of boxwood leafminer damage | Burkholder PHC

Systemic insecticides, soaps, and horticultural oils can effectively control leafminers. These pesticides and insecticides should be cautiously applied.

Because these pesticides can have adverse side effects on other plants or beneficial insects, a plant health care expert should be the one using these treatments. In addition, proper cultural practices, such as regular pruning, fertilization, and irrigation, can help prevent and minimize boxwood leafminers’ impact.

Contact Burkholder Brothers for Plant Health Care Services

If you want to keep your plants healthy and prevent the damage boxwood leafminer populations can cause, contact Burkholder PHC for a consultation. We are a team of certified professionals with decades of experience caring for and maintaining healthy plants and trees for Main Line residents. In addition, we have up-to-date knowledge of the latest and best practices on plant health care and pest control methods. For more information on our services, contact us today.