Northwest berry Foundation

Management Detail

Mites, Twospotted spider

in Strawberries

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Latin name: Tetracanychus urticae


Mites feed by sucking the contents out of leaf cells, causing a mottling of the leaves. They feed mostly on older leaves, which reduces plant vigor and can negatively affect yield. Adult mites are about 0.02 inch long. They have eight legs and are light tan or greenish in color with a dark spot on each side of their back. In fall and again in spring, overwintering forms appear as bright orange globules.



  • Several mite-sampling procedures have been developed. A relatively simple way is to follow the procedures for sampling aphids to optimize scouting time.
  • Sample at least ten sites (unless field is less than one acre). Collect 3 trifoliate young-mature leaves. Count the number of mites per leaf.
  • Very generally, 5 mites per leaflet indicates the threshold for treatment but this involves many mitigating factors.
  • Populations of predatory mites and other beneficial insects need to be monitored and considered closely. Natural controls often make treatments unnecessary.
  • Hot, dry weather and/or dusty areas of the field favor mite development.
  • If not monitoring closely, watch fields for a fading out of color that indicates mite feeding.

Cultural Controls:

  • Avoid dusty conditions. Control road dust.


For information about chemical controls, check with our Pesticide Guide.


Spider mite


Mites and eggs


Stethorus larvae - biological control for twospotted spider mites - photo by C. Chan

Stethorus adult - biological control predator for mites - photo by C. Chan


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