Controlling Caterpillars on Maple Trees: Sprays vs. Trunk Injections

Why Trunk Injections Fail for Leaf-Feeding Caterpillars

Systemic injections (like those using "plugs") rely on transpiration to move insecticide from roots to foliage. For short-lived leaf feeders, the chemical often doesn't reach leaves in time. Worse, injection wounds on thin-barked maples invite decay fungi and borers.

Effective Spray Options

• Bacillus thuringiensis (Bt): Apply to new leaves before caterpillars exceed ¾ inch. Must be ingested; some defoliation occurs before death.
• Contact insecticides: Sevin (carbaryl) or Orthene (acephate) provide quick knockdown when sprayed on foliage.

Timing Is Critical

Treat at first sign of feeding. Late applications after caterpillars mature are ineffective. Always follow label rates and avoid spraying during bloom to protect pollinators.