Stippling is the speckled look of a leaf covered in hundreds of tiny pale or white dots. Each dot is a cell, or a small group of cells, emptied by a feeding mite or insect. On cannabis it is the classic early sign of two-spotted spider mites, usually seen on the upper surface while the mites feed underneath (Utah State University Extension).
In practice
When you see stippling, turn the leaf over and use a 10-30x lens: spider mites, round eggs, cast skins and fine silk confirm it. Heavy stippling merges into a bronzed, grey or dusty look and the leaf yellows. Calcium spots differ: they are fewer, larger and irregular, and no insects are present.
Don't confuse with
- Thrips damage: silvery, papery streaks with tiny black dots of excrement.
- Calcium spots: rust-brown patches with no pests underneath.
- Septoria leaf spot: larger spots with dark margins and black fruiting bodies.
Tetranychus urticae, the commonest cannabis mite indoors: a 0.5 mm sap-feeder that stipples leaves pale and spins webbing, breeding fastest in hot, dry rooms.Slender insects about 1-2 mm long, chiefly western flower thrips (Frankliniella occidentalis), that rasp leaf surfaces, leaving silvery streaks dotted with black frass.A fungal leaf disease caused by Septoria cannabis that produces tan to grey spots with dark margins and yellow halos, starting on lower leaves.A small handheld magnifier, typically 30-60x for cannabis use, used to inspect trichome heads and spot pests and male flowers.Systematic, regular inspection of plants, traps and roots to detect pests and disease early, identify them correctly and record numbers for decisions.
