WSU Extension

Hortsense

Common Insects, Mites & Vertebrates
 
Aphids 
Asian lady beetle 
Bark beetles 
Brown marmorated stink bug 
Brown soft scale 
California gallfly 
Conifer aphids 
Cottony camellia scale 
Cutworms and loopers 
Deer damage 
Earwigs 
Eriophyid mites 
Exotic longhorned beetles 
Fall webworm 
Inchworms 
Leafhoppers 
Leafminers 
Leafrollers 
Lecanium scale 
Oystershell scale 
Pamphilid sawflies 
Pear slug 
Root weevils 
Sapsucker damage 
Shothole borer 
Skeletonizers 
Slugs 
Sowbugs, pillbugs, and millipedes 
Spider mites 
Spotted wing Drosophila (SWD) 
Tent caterpillars 
Voles 



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Caption: Spider mites under microscope
Photo by: L.K. Tanigoshi
  
Common Insects, Mites & Vertebrates : Spider mites
(revision date: 4/30/2013)


Biology
Several species of spider mites may become significant pests on ornamental plants. Spider mites are very small, eight-legged arthropods that damage foliage with their piercing mouth parts. They are usually found on the undersides of leaves. Strands or mats of silk webbing may be present on the underside of infested leaves or in the axil between leaf and stem. Cast skins, eggs, egg shells, and living mites are all commonly present in the webbing. Mite damage begins as a fine yellow or bronze stippling or speckling of leaves. Large infestations may result in overall yellowing or bronzing of affected foliage. Severely damaged leaves may drop from the plant. Hot, dry conditions and high levels of nitrogen in the leaves favor mite infestations.
Management Options

Non-Chemical Management
  • High levels of nitrogen in the foliage encourage spider mite reproduction. Switch to a slow-release or low-nitrogen fertilizer when practical.
  • Hose mites from plants with a strong stream of water.
  • 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.
  • Provide proper culture. Healthy plants are more tolerant of damage, while drought-stressed plants are more susceptible.
Select non-chemical management options as your first choice!

Chemical Management

If nonchemical management options do not give satisfactory control, insecticides may be effective in managing mite populations. However, the insecticide must be registered for the host plant. Find a list of registered pesticides for a specific host by referring to the fact sheet for spider mites on that host.

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