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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis

Spruce Spider Mites

Posted by John Fulton -

The spruce spider mite is one of the main reasons we have generally ugly, old spruces in our area. The mites cause the death of branch tips on spruce trees, and give the appearance the trees are dying from the ground up. Of course, there are other diseases that give similar symptoms, but the spruce spider mite is an every-year occurance.

Generally, the spruce spider mite starts earlier in the season than many of its relatives. Late March isn't uncommon, but April is more like it to have these small pests causing damage. There is also a corresponding time in the fall from lat September through early November. The mites suck plant juices out, and inject toxins back into the plant. Feeding damage first shows as small brown spots (small as in using a magnifying glass). From a distance, damaged needles may appear mottled or bronze.

To check for spruce spider mites, hold a sheet of white paper under affected branches. Shake the branches, and check for "moving dust specks." Larger moving specks may be predatory mites. If they are smashed on the paper, the predatory mites generally leave a red streak. If several predatory mites are present, there is usually no need to apply a control.

Controls for spider mites might include a hard stream of water to knock them off the plants. Of course, this is only a temporary solution. Sprays of insecticidal soap, bifenthrin, or a summer oil will control populations by killing the mites. A new product acequinocyl (Shuttle) has just come on the market for mite control, but may be hard to find in the area. Controls should be applied before mid-May to prevent egg laying for the next generation during the spring, and by mid-October for the fall period.

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