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Predator mites
(Phytoseiidae) play an extremely important role in the
management of spruce spider mite because they feed
mainly on eggs and smaller mites. These mites are
highly effective egg predators and
in fact outbreaks of the spruce spider mite often
follow applications of pesticides that disrupt the
predator mite population.
Overhead watering
combined with low toxicity insecticidal soap alone are
very effective treatments for spruce spider mites
during the growing season (see Using
Insecticidal Soap To Control Spider Mites).
Applications of insecticidal soap won't disrupt
predator mites. During late winter, on the other hand,
mite eggs that are found on needles and stems can be
controlled with horticultural oils.
Certain synthetic
pesticides like carbaryl
(Sevin) are known to be particularly harmful to
predator mite populations and use of these materials
can often guarantee
an outbreak. Therefore use pesticides
carefully and always monitor for spider mite
buildup following applications especially in
susceptible plants.
Spruce
Spider Mite Guide (pdf)
Christmas
Tree Pests (Oregon, 2005) (pdf)
Adelgids on Conifers
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