Table Grape IPM Program: Identifying Spider Mites

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Identifying Spider Mites and Their Damage

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Pacific spider mite
Willamette spider mite
Spider mite eggs

Pacific spider mite damage
Willamette spider mite damage

Because they are so similar in appearance, it is difficult to discern between the Pacific and Willamette spider mites unless they are side-by-side. The Pacific mite is larger in size than the Willamette spider mite. Pacific spider mite forelegs are reddish in color, while Willamette spider mite forelegs are translucent to pale yellow. Names link to more information on identification and management.

Click on photos to enlarge

Spider mites

Adult pacific spider mite
Pacific spider mite (adult, female)
Identification tip: The first pair of legs of this spider mite are reddish.

Willamette female spider mite
Willamette spider mite (adult, female)
Identification tip: The first pair of legs of this mite are translucent to pale yellow.

Spider mite eggs are tiny, translucent and spherical.

Damage

Spider mites damage between veins
Pacific spider mite
Identification tip: Pacific spider mites feed between leaf veins leaving a round spot. This distinguishes them from Willamette mites that feed along the veins.

Willamette spider mite damage
Willamette spider mite
Identification tip: Willamette spider mites characteristically feed along leaf veins. Notice that yellowing is along the veins in the photo above.

Pacific spider mite
Feeds on leaves that are exposed on the sunny side of the canopy. When populations are high they will web on shoots and leaves found at the top.

Williamette spider mite damage.
Willamette spider mites characteristically feed on the shaded part of the canopy.

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