Boxwood Leafminer

Since boxwood leaf miner is an early spring insect, soil applications must be done late in the previous growing season, or very early in the current growing season to obtain acceptable control. If soil applied systemic products are not applied in time, a foliar application of Orthene can be applied in April or May when the weigela are blooming to obtain control in the current growing season.

Treatment Strategy

Since boxwood leaf miner is an early spring insect, soil applications must be done late in the previous growing season, or very early in the current growing season to obtain acceptable control. If soil applied systemic products are not applied in time, a foliar application of Orthene can be applied in April or May when the weigela are blooming to obtain control in the current growing season.

Other Treatment Practices

  • Pruning the foliage before adult emergence or after egg laying end will reduce the overall population.

Soil Application or Limb/Foliar Spray Using Transtect

Soil Application or Limb/Foliar Spray Using Xytect 2F

Soil Application or Foliar Spray Using Xytect 75WSP

Foliar Spray Using Lucid

Expected Results

Soil applications are extremely effective against this pest. Xytect and Transtect can also be applied as foliar sprays and will provide translaminar movement and good control as well. For small to medium size shrubs or hedges consider using lower dosage rates. Lucid will control both leaf miner and spider mites

Signs of Damage

  • Boxwoods infested with this leafminer develop blisters on the lower leaf surface
  • Infested leaves are usually smaller, off-color and drop sooner than healthy leaves
  • Heavily infested boxwoods usually have sparse foliage and poor color
  • The eggs of the boxwood leafminer are white to transparent and can be seen by holding the leaf up to the light
  • The larvae are yellowish-white and approximately 1/8” long
  • The adult boxwood leafminer is an approximately 1/10” long, delicate, orange-yellow to red, gnat-like fly
  • The larvae feed between the upper and lower layers of leaves

Photo: Brian Kunkel
University of Delaware, Bugwood.org

Photo: John A. Weidhass
Virginia Polytechnic Institute and State University Bugwood.org

Trees At Risk

All boxwoods may be infested, but more slowly growing English varieties are less susceptible than American varieties.

  • Littleleaf boxwood (Buxus microphylla)
  • Common boxwood (Buxus sempervivens)

Biology

  • The partly grown larvae overwinter within their mines in the leaves of the host plant.
  • The larvae grow rapidly as the weather begins to warm. In late April, they turn into orange-colored pupae and emerge as a fly.
  • After mating, the female inserts her eggs deep into the leaf tissue (249-700 GDD). She dies soon after and the eggs hatch approximately 3 weeks later.
  • One generation per year.

A Treatment Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments by forestryimages.org

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