White Bumps on Mexican Petunia Stems: Scale or Whitefly? Oil Treatment Works

Small bumps on healthy, blooming Mexican petunia stems. Likely scale insects or whitefly nymphs. Both succumb to horticultural oil.

Treatment

1. Mix paraffin oil (Parafine, Ultra-Fine, or Neem) per label.
2. Spray late afternoon (cooler, no sun burn risk).
3. Let work overnight.
4. Next morning: blast with hose on stream setting to wash off oil + dead pests.
5. Repeat next evening. Two rounds usually clears it.

Why Oil?

Mechanical suffocation—no resistance buildup. Safe for pollinators once dry. Cheap, available at hardware stores.

Monitor new growth; retreat if crawlers reappear.