Maple Borer Damage in Toronto: Imidacloprid Treatment and Wire Method

12-year-old Toronto maple with wet trunk wound, borer activity, canopy decline—active infestation requiring imidacloprid (Merit/Onyx) or mechanical wire control + fertilization.

Borer Diagnosis Confirmed

• Wet wound = active feeding
• Canopy dieback = girdling progressing
• Wood-boring larvae destroying vascular tissue
• Entry point for pathogens

Treatment Options

Chemical (If Available in Canada)

• Imidacloprid (Merit) or cyfluthrin (Onyx) trunk spray
• Soil drench for systemic uptake
• Check local regulations—some restricted

Mechanical (Non-Chemical)

• Flexible wire into entry holes to skewer larvae
• Labor-intensive but effective for few holes
• Repeat as new holes appear

Vigor Restoration

• Fertilize: 1-10-10 at 1 lb/inch trunk diameter
• Apply before rain
• Water deeply
• Mulch 3" to dripline

Stressed trees attract borers. Vigor + direct control = best outcome. Monitor closely.