White spots on leaves

Overview

White spots can be fungal (powdery mildew: uniform coating), parasitic (mealybugs: cottony patches) or abiotic (limescale from hard water: white dots that dissolve in vinegar).

Differential diagnosis

Uniform powdery coating → powdery mildew.

Cottony clusters at nodes → mealybugs.

Hard shiny dots → limescale.

Natural remedies

Diluted milk 1:10 sprayed on leaves fights mildew. For mealybugs: alcohol-dipped cotton bud.

Treatments

Micronized sulfur for mildew. Horticultural oil for mealybugs. Rainwater for limescale.

Prevention

Ventilate, space plants, use low-residue water.