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The information accessed from this screen is based on the publication: Marshall, Valin G. 1986. Spruce spider mite in British Columbia. Forestry Canada, Forest Insect and Disease Survey, Forest Pest Leaflet No. 33 4p.
The spruce spider mite, Oligonychus ununguis (Jacobi) (Acari: Tetranychidae), is an important pest of forest and ornamental conifers. The last serious outbreak in British Columbia occurred in 1975 on immature Douglas-fir north of Kelowna when 800 ha were damaged.
Conditions favoring outbreaks are: hot dry weather, overstocked stands, poor sites, susceptibility of some tree species, and absence of natural enemies due to a heavy coating of dust on the foliage or to insecticides that drift to the conifer foliage from adjoining agricultural areas.
Extreme temperatures, strong winds accompanied by heavy rain, and prolonged high humidity limit abundance of the spruce spider mite.
For more information, see the Spruce Spider Mite Forest Pest Leaflet in the Canadian Forest Service bookstore.