WSU Extension

Pestsense

Caption: Spider mites
Photo by: unknown
  
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Spider mites

(revision date: 5/4/2022)


Use Integrated Pest Management (IPM) for successful pest management.

Biology
Spider mites are common pests of indoor plants, thriving in the warm, dry conditions found in most homes. Each tiny eight-legged, spider-like mite is about the size of a period and can best be seen with magnification. The two-spotted spider mite is one of the most common pests, and is straw-colored, often with two dark blotches on the body. These pests puncture and feed on the underside of the leaves, causing yellowish to bronze to silvery "stippling" to appear on the leaf surface. Middle-aged leaves tend to show the earliest symptoms. A large infestation can cause yellowing, wilting, and leaf drop. Spider mites produce strands of silk, much like a spider. This webbing is often visible on the underside of leaves and between leaves and stems. The mites may be seen crawling about on the webbing. Spider mites can be introduced with new plants, by bringing outdoor plants inside to overwinter, or through open screens during summer months. Healthy plants can usually tolerate low levels of mite infestation, but response to mite damage varies widely with plant species.
Management Options

Non-Chemical Management
  • Do not move plants inside from outdoors. If you must move plants indoors, they should be quarantined (for example, in a spare bedroom) and kept isolated from other indoor plants for about a month. During this time, regularly inspect the quarantined plants for pest problems. Treat pest problems as necessary and continue isolation until the plants are “clean” for at least one full month before integrating them with the rest of your plant collection.
  • Quarantine and monitor newly purchased plants or plants from your collection which have become infested. Spider mites move from plant to plant primarily by leaf contact, walking, or drifting in the air on strands of webbing, so isolation will help protect other plants.
  • Spider mites thrive in hot, dry environments. Increase humidity around plants by resting plant pots on (not in) pebble-and-water-filled trays, by daily misting, or by other means. Do not overwater plants in an attempt to increase humidity.
  • Keep plants healthy with proper water, nutrition, and growing conditions for the species. Strong plants growing in good conditions will tolerate damage more easily than weak or unhealthy plants.
  • Heavily infested plants may be too damaged to survive and pose a risk to any other plants in the household. Get rid of them!
  • Light to moderate infestations may be adequately controlled by rinsing plants thoroughly in the shower or sink with lukewarm water. Pay particular attention to the underside of all leaves. This should be repeated at least weekly for best results. A plastic bag may be wrapped around the pot and soil to prevent soil from spilling out and clogging the drain.
Select non-chemical management options as your first choice!

Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Chemical controls are NOT RECOMMENDED on edible plants (i.e. herbs, salad greens, etc.) grown indoors for culinary use. Thorough coverage including the underside of leaves is essential. When practical, take houseplants outdoors to a shaded location before applying chemical controls. Allow sprays to dry thoroughly before returning plants indoors.

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
  • Safer Insect Killing Soap II with Seaweed Extract
    Active ingredient: potassium salts of fatty acids  |  EPA reg no: 42697-59
  • Safer Brand End All Insect Killer
    Active ingredient: neem oil, clarified hydrophobic extract of neem oil, potassium laurate, pyrethrins  |  EPA reg no: 59913-14
  • WHITNEY FARMS INSECTICIDAL SOAP
    Active ingredient: POTASSIUM LAURATE  |  EPA reg no: 67702-21-73327
  • This list may not include all products registered for this use.
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Caption: Spider mites
Photo by: unknown