Boxwood Leafminer

Background

• Origin: Arrived in Chicago from the East Coast 9 years ago.
• Description: Small, gnat-sized insects with larva that feed on internal cells of the leaves. They are exclusive to boxwood.
• Life Cycle: Adults emerge in late May from leaves, larvae feed inside leaves since the previous May.

Treatment Solutions

• Simple Solution: Annual soil drench based on shrub height.
• Measurement: 3 ounces of Bio-Advanced Insecticide per foot of shrub height, mixed with one gallon of water.
• Application: Pour mixture at the root collar, which absorbs 60% of nutrients.
• Effectiveness: Active ingredient spreads in 5-10 days, protects for 12 months.

Plant Health

• Preventative treatment: Fertilize once per month May, June and July; monitor rainfall weekly and supplement with water if there is not 1.5 inch of rain.
• Optional Product: Combined insecticide and fungicide available and recommended for best control.
• Photo displays: Boxwood leaf with the back epidermal layer peeled off showing larva that were living inside the leaf eating the mesophyll cells. They pupate inside the leaf in early May, chew an exit hole and fly above the plant finding a mate, the lay eggs on the newly forming leaves to start the life cycle again.

Photo credit: Missouri Botanical Garden