Rhizina root disease

Rhizina undulata

Rhizina root disease girdles planted and newly regenerated seedlings on sites where fire occurred less than 2 years prior.  Much of the information on this disease in BC comes from a period when slash-burning after harvest was a common silvicultural prescription.

During this period approximately half of all slashburned sites had some evidence of Rhizina mortality.

One this page:

• Description
• Host tree species
• Damage symptoms
• Identification images

Description

This pathogen is the highest hazard within 2 years after moderate burns in the ICH (Interior Cedar Hemlock) and CWH (Coastal Western Hemlock) biogeoclimatic zones. Sites with acidic soils, previous old growth forests, or a history of western hemlock are at highest risk.

Host tree species

Seedlings of all native conifer species are susceptible to rhizina root disease, although western redcedar: Engelmann, Sitka, and white spruce; lodgepole pine; Douglas-fir; western larch and western hemlock are the most common hosts. This disease also affects fire weed and the lack of fireweed may be an early indicator that the disease is present.

Damage symptoms

The foliage of infected seedlings become discoloured and trees are killed by girdling at or below the soil line. 

Tan-colour strands, 1 to 2 mm in diameter, are usually interwoven with the root systems of infected seedlings. Fruiting structures are very distinct, up to 6 cm in diameter, and grow within 50 cem of infected seedlings. The fruiting bodies are chestnut to dark brown or black with many brain-like lobes and fissures. The fruiting bodies may grow en masse.

Identification images

Further reading

Read the unabridged field guide text and view images of laminated root rot in the Field Guide to Forest Damage in B.C. (PDF, 6.5MB)