DiseaseMedium Severity

Douglas Fir Phomopsis Canker

Phomopsis lokoyae

A fungal canker disease specifically affecting Douglas fir trees throughout California and Oregon. The disease causes long, narrow cankers that can girdle entire branches in one season, particularly targeting saplings on poor sites and stressed mature ornamental trees.

Peak Season: Infection: Through needle scars and wounds year-roundSpore production: During wet seasonsPeak activity: Periods of persistent rain or fogCanker development: Progressive throughout growing seasonVulnerability: Highest during stress periods
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Douglas fir Phomopsis canker showing characteristic narrow girdling lesions and branch dieback

Identification & Symptoms

What to Look For

Long, narrow cankers on branches, usually pointed at ends
Cankers may girdle entire branches in one season
Branch mortality from girdling action
Particularly severe on saplings on poor sites
Individual branch attacks on stressed mature trees
Spore fruits (pycnidia) visible at canker edges during wet weather

Potential Damage

Branch girdling leading to mortality
Progressive weakening of tree structure
Increased susceptibility in stressed trees
Economic losses in ornamental plantings
Reduced tree vigor and aesthetic value
Secondary infections through compromised areas

Lifecycle

The fungus enters through needle scars or wounds, establishing cankers at infection points. It successfully attacks stressed trees by girdling branches. During wet seasons, spores are produced in pycnidia at canker edges and spread to other tree parts or adjacent trees.

Professional Treatment Approach

1

Fungisol applications for canker disease management

2

Address stress factors: malnutrition, improper irrigation, poor soils

3

Minimize wounding from squirrels, birds, improper pruning, climbing spurs

4

Improve site conditions to reduce tree stress

5

Remove severely cankered branches when feasible

Recommended Mauget Products

Fungisol

Professional-grade treatment specifically effective against douglas fir phomopsis canker.

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