Identifying and Controlling Boxwood Leaf Miner

If your boxwoods have developed a mottled, yellow-brown appearance on last year's growth, they are likely hosting the boxwood leaf miner. This tiny pest becomes noticeable in August when the damage peaks.

Life Cycle and Damage

In spring, a small, fly-like adult lays eggs on the undersides of new boxwood leaves. Once hatched, the larvae tunnel into the leaf tissue, feeding safely between the upper and lower surfaces. Their mining creates the characteristic blotchy, discolored patches that mar the foliage.

Effective Control Strategies

Because the larvae are protected inside the leaves, they are difficult to reach with contact insecticides. The most effective approach targets the vulnerable adults in April and May.

• Timing: Begin applications three weeks after new spring foliage emerges.
• Products: Insecticidal soap or horticultural oil, applied thoroughly to cover all leaf surfaces.
• Schedule: Make three weekly applications.
• Systemic option: Systemic insecticides absorbed by the plant can kill larvae feeding inside the leaves.

Pruning damaged foliage now will not harm the shrubs, but plan to treat for miners next spring to prevent a recurrence.

boxwood leaf miner (image courtesy of Jim Baker, North Carolina State University, Bugwood.org)

leaf miner maggots (image courtesy of Brian Kunkel, University of Delaware, Bugwood.org)