Spider mites
Tiny sap-sucking mites that thrive in hot, dry conditions, causing speckled, dull leaves and fine webbing.
Also known as: Red spider mite, Two-spotted spider mite
Symptoms and identification
Fine pale speckling on the upper surface of leaves, which later turn dull, bronze or yellow and drop. Fine silky webbing appears between leaves and stems in heavy infestations. Tiny moving dots are visible on the undersides of leaves; tapping a leaf over white paper shows them clearly.
Causes
Spider mites multiply extremely quickly in hot, dry air, including air-conditioned rooms and sunny balconies in summer. Dusty leaves, drought-stressed plants and the use of broad-spectrum insecticides that kill their natural predators all make outbreaks worse.
Organic treatment
Hose or shower the plant thoroughly, especially under the leaves, to knock off mites and webbing. Follow with insecticidal soap or neem oil spray every 5–7 days for at least three weeks, since eggs keep hatching. Badly infested shoots should be cut off and binned.
Prevention
Keep plants well watered and raise humidity around indoor plants. Rinse or wipe leaves regularly to remove dust, and check the undersides of leaves weekly in dry weather. Keep new plants apart for two weeks before placing them near others.
Chemical treatment (use with care)
For persistent infestations, use a miticide (acaricide) labelled for spider mites, as many general insecticides do not kill them. Follow the label and rotate between products with different active ingredients.