Symptom
White or silver speckles
Pale speckling is often the work of mites, thrips or leafhoppers feeding on individual cells. Papery patches from scorch and the early spots of powdery mildew can look similar.
Rub the leaf and look underneath with a lens. Powder that wipes off is mildew; tiny moving specks are mites; silvery streaks with black dots are thrips.
Likely causes
Ordered from the usual answer to the less likely one. Each links to the full problem.
Recorded on Rosemary
-
Pest Common
Spider mites
Fine pale stippling, webbing, in hot dry air. -
Pest Possible
Leafhoppers
Pale stippling with hopping insects. -
Fungal disease Possible
Powdery mildew
White spots that rub off and spread into a coating. -
Pest Less likely
Mealybugs
White, cottony tufts in leaf joints.
Less likely on Rosemary