Boxwoods are a beloved landscape staple in the Virginia and Maryland region, providing year-round greenery and structure to gardens. However, one pest poses a significant threat to these iconic plants: the boxwood leafminer (Monarthropalpus flavus). Despite their tiny size, these pests can cause substantial damage, compromising the health and beauty of boxwoods if left unchecked.

What Are Boxwood Leafminers?

Boxwood leafminers are small, fly-like insects whose larvae feed on the tissue between the layers of boxwood leaves. Female leafminers lay their eggs in late spring, and once hatched, the larvae tunnel inside the leaves to feed, creating unsightly blisters or yellow spots on the foliage. Infestations often go unnoticed until these visible symptoms appear.

Signs of Boxwood Leafminer Infestation

If you suspect your boxwoods may be under attack, look for:

• Discolored leaves: Yellow or orange blotches on the foliage.
• Blistered leaves: Bulging, uneven leaf surfaces.
• Defoliation: In severe cases, leaves may drop prematurely.
• Tiny flies around boxwoods in spring: Adult leafminers are active and laying eggs during this time.

Impact on Boxwoods

The humid and temperate climate of the mid-Atlantic region creates an ideal environment for boxwood leafminers to thrive. Infestations can weaken the plants, making them more susceptible to other stressors such as drought, fungal diseases, or winter damage. Left unmanaged, the cumulative stress can lead to the decline or even death of the plant.

Managing Boxwood Leafminer Infestations

Managing these pests requires a combination of preventative care and timely treatment. Here are some strategies:

1. Regular Monitoring: Inspect your boxwoods throughout the year to catch signs of an infestation early.
2. Pruning: Remove and dispose of heavily infested branches during the dormant season to reduce the pest population.
3. Chemical Control: A targeted insecticide application in late spring, when adults are active, can help control the pest. Systemic treatments can also be applied in early spring or fall to protect new growth.
4. Biological Control: Introducing natural predators, such as certain parasitic wasps, can help keep the population in check.
5. Professional Care: Enlist the help of certified arborists, like those at Titan Tree Care, who can assess the severity of the infestation and recommend tailored solutions.

Prevention Tips

The best defense is a healthy plant. Here’s how you can help prevent future infestations:

• Choose Resistant Varieties: Some boxwood species are less attractive to leafminers than others.
• Maintain Plant Health: Proper watering, mulching, and fertilization will strengthen your boxwoods and improve their resilience against pests.
• Integrated Pest Management (IPM): Work with professionals to develop a year-round pest management plan.