# Spider mites

- URL: https://backyardgrapes.com/diseases/spider-mites/
- Scientific name: Tetranychus and Eotetranychus spp.
- Category: Insect / pest
- Affects: Leaves
- Severity: moderate
- Favored by: Hot, dry, dusty weather; flares up when broad-spectrum sprays kill the predatory mites.
- Easily confused with: Grape leafhopper, Grape erineum mite

**Summary:** Tiny sap-sucking mites that stipple and bronze leaves in hot, dusty, dry conditions.

**What to look for:**
- Fine pale stippling or speckling across the leaf, giving a dull, sandblasted look.
- Leaves bronze (on red varieties) or yellow (on white) as feeding intensifies.
- Fine webbing on the leaf underside in heavy infestations.
- Scorched, curling, dropping leaves and reduced vigour, worst on dusty rows and water-stressed vines.

**Treatment — Cultural / prevention:**
- Reduce dust on and around the vines (dust flares mite outbreaks).
- Keep vines adequately watered; drought stress makes damage worse.
- Avoid unnecessary broad-spectrum insecticides that wipe out mite predators.

**Treatment — Organic / low-toxicity:**
- Conserve or release predatory mites, the main natural control.
- Horticultural oil or insecticidal soap, and strong water sprays to the leaf underside.

**Treatment — Conventional (chemical):**
- A selective miticide only if damage passes a threshold; avoid products that kill predators.

Spider mites are barely visible sap-feeders that live on the undersides of leaves and
thrive in hot, dry, dusty conditions. Each bite empties a leaf cell, so heavy feeding
turns leaves dull and stippled, then bronze or yellow, and finally scorched and dropping.
In bad infestations you'll see their fine webbing strung across the leaf underside.

A key point for control: spider mites are often a problem we create. Broad-spectrum
insecticides sprayed for other pests kill the predatory mites and insects that normally
keep spider mites in check, and a mild population then explodes. So the first line of
defence is to conserve those natural enemies, cut the dust, and keep vines from drying
out — reaching for a selective miticide only when damage genuinely warrants it.

**Image credits:**
- Spider mites (Tetranychus sp.) and their eggs on a leaf surface — [Photo: Ken Gray Insect Image Collection, Pacific Northwest Pest Management Handbooks](https://pnwhandbooks.org/insect/vegetable/vegetable-pests/hosts-pests/cucumber-spider-mite)

**Sources:**
- [Webspinning Spider Mites / Grape / Agriculture: Pest Management Guidelines](https://ipm.ucanr.edu/agriculture/grape/webspinning-spider-mites/) — UC IPM
- [Grape-Spider mite](https://pnwhandbooks.org/insect/small-fruit/grape/grape-spider-mite) — Pacific Northwest Pest Management Handbooks (OSU/WSU/UI)
- [Grape: Spider mites](https://hortsense.cahnrs.wsu.edu/fact-sheet/grape-spider-mites/) — Washington State University Extension (Hortsense)
- [Grape Year-Round IPM Program: Identifying Spider Mites](https://ipm.ucanr.edu/PMG/C302/m302bpspmites.html) — UC IPM