Boxwood Leafminer: Eating Your Boxwoods From The Inside Out

Boxwood Leafminer Larva

Boxwood Leafminer Larva & Blisters On Underside Of Leaf

Boxwood Leafminer, Monarthropalpusi flavus (Schank), is a small mosquito looking insect about 1/8th of an inch long that causes serious damage to boxwoods. Despite the size, leafminers are easy to spot because of their bright orange color.

Like a lot of other spring pests, boxwood leafminers are an invasive species native to Europe. They were brought to the United States in the mid-1600s when boxwoods themselves were introduced. Known as “Man’s Oldest Garden Ornamental” and for being a low maintenance shrub, many homeowners have boxwoods on their property and are at risk for leafminers.

Boxwood Leafminer Adult Fly

Boxwood Leafminer Adult Fly

Keep An Eye Out:

In the next week or so you should begin seeing leafminers emerge. These orange adult flies can be seen swarming around or clinging to boxwoods for about 2 weeks in early spring.

Although, this is the time you begin seeing adult leafminers, the real damage to your boxwoods in the larva stage. Before the adult flies dies, they lay their eggs in the leaf tissue. When they hatch, the maggots feed on the inside of the leaf causing the telltale symptoms listed below. Once it’s warm enough they emerge from the leaf as adults. This means if you see leafminers on your boxwoods this year, they will show up next year and the year after that, damaging your boxwoods more and more until dealt with.

Boxwoods infected with this leafminer will experience numerous symptoms and develop an unsightly appearance including;

Boxwood Leafminer

Boxwood Leafminer Leaf Discoloration

Boxwood Leafminer Symptoms:

  • Blisters on lower leaf surface
  • Smaller leaves
  • Off color leaves
  • Early leaf drop
  • Sparse Foliage When Heavily Infested
  • Poor Color When Heavily Infested

Species Susceptible to This Insect:

All boxwoods are susceptible to this insect; however, American varieties tend to be more susceptible than the slower growing English variety.

If you’re thinking of planting boxwoods opt for the English varieties such as Buxus sempervirens Pendula, Suffruticosa, Handworthiensis, Pyramidalis, Argenteo-varigata and Varder Valley, which are more resistant to leafminers.

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There are numerous different treatments available for Boxwood Leafminers. These treatments vary based on the pest’s point in the life cycle. Treatments are also based on the specifics of your landscape. For example, a boxwood planted near a vegetable garden will require a different treatment than a boxwood that isn’t near anything else on the property.

A Certified Arborist that follows Integrated Pest Management (IPM) Protocol will be able to diagnose and prescribe the right treatment at the right time for your property to get rid of boxwood leafminers.

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Samantha Huff

Samantha Huff is the marketing coordinator at RTEC Treecare. She enjoys learning about the technical aspects of trees and the insects and diseases that prey on them. She hopes that these articles can help homeowners gain control of their tree and shrub maintenance by being aware of the signs and symptoms of unhealthy trees.

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