WSU Extension

Hortsense

Tomato : Spider mites
(revision date: 2/14/2019)


Biology
Spider mites are tiny, eight-legged mites which range in color from yellowish to green or red. They typically feed on the underside of leaves, causing a yellowish to bronze stippling or speckling of leaves. Severe infestations can cause entire leaves to turn yellow. Spider mite feeding is usually accompanied by webbing on the underside of leaves. The mites may be visible as "moving dust" in the webbing. Mite infestations are worse in hot, dry, dusty conditions.
Management Options

Non-Chemical Management
  • Provide proper culture. Healthy plants are more tolerant of damage, while drought-stressed plants are more susceptible.
  • Predatory mites and insects such as ladybird beetles and green lacewings aid in control of mite populations. Avoid use of broad-spectrum insecticides which kill beneficials.
  • Hose mites from plants with a strong stream of water.
  • High levels of nitrogen in the foliage encourage spider mite reproduction. Switch to a slow-release or low-nitrogen fertilizer when practical.
Select non-chemical management options as your first choice!

Chemical Management

Begin monitoring for spider mites in late spring or especially during hot weather. Insecticidal soap may require more than one application. Do not make more than 3 sequential applications over a 2-week period.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Mite X RTU
    Active ingredient: clove oil, cottonseed oil, garlic oil/powder  |  EPA reg no: 4-04001
  • RID-BUGS
    Active ingredient: clove oil, cottonseed oil, garlic oil/powder  |  EPA reg no: 998920-08001
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Insect Killing Soap with Seaweed Extract II [Organic]
    Active ingredient: potassium laurate  |  EPA reg no: 42697-59
  • This list may not include all products registered for this use.
Images
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Caption: Spider mites under microscope
Photo by: L.K. Tanigoshi
Caption: Spider mite damage on leaf
Photo by: A.L. Antonelli
Caption: Spider mites and eggs under microscope
Photo by: Unknown