WSU Extension

Hortsense

Spruce
 
Disease
Oil discoloration of foliage 
Rhizosphaera needle cast 
Rust 
Insect
Coneworms 
Cooley spruce gall adelgid 
Douglas fir tussock moth 
Pine needle scale 
Spruce aphid 
Spruce bud scale 
Spruce budworm 
Spruce needleminer 
Spruce spider mite 
White pine weevil 



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Caption: Spruce spider mite damage
Photo by: R. Maleike
  
Spruce : Spruce spider mite
(revision date: 3/10/2017)


Biology
The presence of spruce spider mites is indicated by yellow stippling near the needle bases, usually on the lower branches and spreading upwards as the mite population increases. Damaged needles may turn reddish-brown. Fine webbing may cover the needles and twigs. The actual spider mites are very small and vary in color from greenish to orange, dark green, or black, with orange legs. These mites are often worst on dusty roadside trees.
Management Options

Non-Chemical Management
  • Spider mites are probably controlled naturally by predatory mites and rain.
  • Try to avoid broad-spectrum insecticides that will kill predatory mites and allow a spider mite population explosion.
  • Hose plants with strong stream of water to wash off spider mites (where practical).
Select non-chemical management options as your first choice!

Chemical Management

Begin monitoring for spider mite in the late spring or especially during hot weather. Horticultural oils, soap-based products and some other products may cause discoloration of spruce needles, particularly on Colorado blue spruce. Read labels carefully and test on a small area before application. DO NOT APPLY Safer Brand Insect Killing Soap Concentrate II to Colorado blue spruce. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Naturalis L
    Active ingredient: Beauveria bassiana  |  EPA reg no: 53871-9
  • Safer Brand Insect Killing Soap Conc II [Organic]
    Active ingredient: potassium laurate  |  EPA reg no: 42697-60
  • This list may not include all products registered for this use.
Images

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Caption: Spruce spider mite damage
Photo by: R. Maleike
Caption: Spruce spider mite
Photo by: C.R. Foss
Caption: Spruce spider mite webbing and damage
Photo by: R.S. Byther