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Spider Mite Alert!
Gretchen Pettis,
Extension Entomologist-IPM Program
Add heat and drought together and you get a recipe for two-spotted spider mite infestations in the landscape and nurseries. Since no respite in the weather is in sight, now is the time to begin scouting for these pests. You may avoid serious plant damage by inspecting now and treating infestations before they become serious.
Two-spotted spider mite is one of the more economically important of the spider mites, attacking over 200 plant species. The most common woody ornamental plants attacked are: azalea, camellia, hollies, viburnum, rose, and pyracantha. Ornamental trees like maple, elm and redbud are particularly susceptible. Watch these commonly infested plants to prevent mite population explosions.
The white paper test is an effective and simple way to scout for spider mites. Hold a piece of white paper 4” - 6” below a shrub or tree branch and vigorously tap the branch 3-5 times. Spider mites, if present will be visible on the white paper. They will be small (like the period at the end of this sentence) and orange in color and move very slowly. If you have a large number of relatively fast moving orangish ‘specks’, chances are good that you have a healthy population of beneficial predatory mites. You may consider holding off on a pesticide application in this case and continue scouting at weekly intervals. You may also send a sample to your local Extension agent for identification if you are unsure.
Overuse of broad spectrum insecticides early in the season, including pyrethroids, can make summer infestations of spider mites worse. Pesticide applications may be necessary for heavy mite populations. Miticides are not effective against the egg stages and mite generations can overlap. Therefore, miticides may need to be applied at 5 day intervals during the summer. Mite populations are often localized so spot treatments should be effective with good scouting. Oils can be effective, but caution must be used to avoid burning plant leaves. In addition to horticultural oils, other controls are insecticidal soap, bifenthrin (Talstar), or disulfoton (Di-System). Apply according to manufacturer's instructions.