Japanese Maple Scale Infestation: Simple WD-40 and Oil Treatment

Rinji's laceleaf Japanese maple shows white cottony masses on stems at 3-4 locations.

Diagnosis: Scale Insects

Soft scales or mealybugs—immobile sap-feeders under waxy covers. "Cotton candy" appearance suggests mealybugs or cottony scale.

Two-Step Treatment

1. Spot treatment (light infestation): Dab each mass with WD-40 on a paper towel. Oil penetrates waxy cover, dehydrating insects. Often sufficient for minor outbreaks.
2. Full spray (heavier infestation): Apply lightweight horticultural oil (e.g., SunSpray Ultra-Fine) thoroughly to stems and leaves. Repeat in 10 days. Spray when temps <85°F.

Why This Works

Oils smother scales physically—no resistance development. WD-40's solvent action helps penetration. Avoid neonicotinoids on maples (pollinator risk).

Monitoring

Check new growth for crawlers in spring. Early detection = easier control.