Lilac White Fuzzy Branches: Powdery Mildew vs. Cottony Aphid

Simple Touch Test Diagnosis

3-year-old lilac with white fuzzy coating on branches (not leaves) in June—two possibilities:

1. Powdery mildew: Dusty, rubs off as powder, static.
2. Cottony aphid: Wet/sticky, moves when touched, honeydew on leaves.

Treatment by Result

If powdery mildew: Usually harmless on lilacs; ignore or spray fungicide (Bayleton, Funginex, Cleary's 3336, Banner) at first sign next year. Spray both leaf surfaces, use spreader-sticker.

If cottony aphid: Spray contact insecticide (Orthene, Talstar, malathion, neem) or systemic (Orthene soil drench). Target crawlers on new growth.

Why the Dog Test Matters

Powdery mildew doesn't transfer in clumps to fur—cottony aphid egg sacs do. This field test is highly reliable.