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Sitka Spruce (Picea sitchensis) Diagnostic Tables

Crown and Needle Symptoms

Symptom

Possible Causes

Visual

Crown yellowing, often with top-down decline and distress crop

Armillaria root disease (Armillaria spp.)

Defoliation and yellowing of older needles. Older trees will be towards the lower crown, young trees near the top

Green Spruce Aphid (Elatobium abietinum) 

Crown Dieback and defoliation of needles leading towards eventual death

Heterobasidion Root Disease (Heterobasidion occidentale)

Example of Heterobasidion Root Disease on Pines (spruce example coming soon)

Trunk and Branch Symptoms

Symptom

Possible Causes

Visual

Butt swelling on older trees, presence of brown rot in heartwood when cored, presence of velvety, brownish layers of cushion-like fruiting bodies at base of tree or on lower trunk

Velvet polypore/Dyer’s polypore (Phaeolus schweinitzii)

 

Phaeolus schweinitizii Fresh Fruiting Body. Source: American Mycological Association

Phaeolus schweinitizii Old Fruiting Body. Source: James W. Byler, USDA Forest Service, Bugwood.org

Black shoestring-like cords and white fans of fungal tissue running up the first few meters of the trunk (under bark), sometimes resin bleeds near base of tree, possible presence of epicormic sprouts

Armillaria root disease (Armillaria spp.)

Close-up of Armillaria rhizomorphs. Source: Terry Henkel

Yellowing needles with branch defoliation and dieback of older needles


AND/OR


Dead or dying older needles covered in sooty mold, not affecting new growth

Green Spruce Aphid (Elatobium abietinum)

Petr Kapitola; Central Institute for Supervising and Testing in Agriculture, Bugwood.org

Elizabeth White, USDA Forest Service, Bugwood.org


Source: Wallis Robinson, UC Cooperative Extension

Fruiting Bodies can be found on the lower trunk of infected trees. Fruiting bodies are the easiest way to identify the disease, but there are look-alikes!

Heterobasidion Root Disease (Heterobasidion occidentale)

(Semantic Scholar , W. Otrosina)