Spider Mites

Spider mites are extremely small, often under half a millimetre long, and are best seen with a hand lens. Colour varies by species and season, from pale green or yellow to reddish, and some species show characteristic dark spots on either side of the body.

Mite vs. insect

Adult mites have eight legs and no antennae, distinguishing them from six-legged insect pests.

Webbing

Fine silk strands on leaf undersides and between leaves, most visible under heavy infestation.

Stippling

Tiny pale or yellow speckles on the upper leaf surface where cell contents have been removed.

Spider mites develop through egg, larval, two nymphal stages, and adult. Development is rapid in warm weather, and a generation can be completed in under two weeks under favourable conditions, allowing populations to build quickly over a season.

Many species overwinter as mated adult females in plant debris, bark crevices, or nearby vegetation, resuming feeding and reproduction as temperatures rise in spring.

Feeding removes chlorophyll-containing cell contents, producing stippling that can coalesce into bronzed or scorched-looking foliage. Severe, prolonged infestations can cause leaf drop, reduced photosynthesis, and yield or quality losses, particularly under hot, dry conditions that also favour the mites.

Spider mites have an unusually broad host range spanning field crops, vegetables, fruit, and ornamentals. Notable hosts include cotton, strawberry, cucumber, and sweet pepper, among many others.

Because early symptoms are subtle, regular inspection of leaf undersides with a hand lens is important, along with a simple shake test over white paper to dislodge and count mites. Monitoring should also note the presence of predatory mites and other natural enemies, since their activity strongly influences whether populations decline naturally.

Spider mite management works best as part of an integrated approach that reduces plant stress and conserves natural enemies rather than relying on reactive treatment alone.

• Conserve predatory mites and other natural enemies by avoiding unnecessary broad-spectrum treatments
• Manage irrigation to avoid drought stress, which favours mite outbreaks
• Reduce dust near crops where practical, since dusty conditions favour mites
• Monitor regularly and use local thresholds to guide any intervention