DiseaseHigh Severity

Cytospora Canker

Valsa kunzei (Cytospora kunzei), V. nivea, V. sordida

A widespread fungal canker disease affecting numerous tree species throughout North America. The disease typically attacks trees weakened by wounds, improper pruning, or environmental stress, causing irregular cankers that can girdle trunks and large branches.

Peak Season: Spore release: Moist spring weather conditionsPrimary infection: Through fresh wounds and cutsSymptom development: Progressive throughout growing seasonSpore horn formation: During wet spring periodsYear-round progression: Once established, continues regardless of season
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Cytospora canker showing characteristic branch canker symptoms and bark discoloration

Identification & Symptoms

What to Look For

Irregular, diffuse cankers on trunks and large branches
Yellow to red-brown spore horns or tendrils in moist spring weather
Diseased bark discolored with black pimples (pycnidia)
Red-brown, water-soaked sapwood beneath cankers
Wilting and discoloration of leaves above cankers
Dieback of small branches and twigs
Copious resin flow on infected conifer branches

Potential Damage

Girdling of trunks and major branches leading to mortality
Progressive branch dieback and crown decline
Weakening of tree structure at canker sites
Secondary infections through compromised bark
Reduced vigor and increased susceptibility to other stresses

Lifecycle

Spores contact wounds or pruning cuts and germinate in moist conditions. The fungus establishes at the boundary between dead and living wood. Waxy spore tendrils are produced in flask-shaped fruiting structures and release spores when wet to create new infections.

Professional Treatment Approach

1

Fungisol applications for disease management on valuable trees

2

Proper pruning techniques to minimize wounds

3

Avoid pruning during wet weather when spores are active

4

Remove and destroy infected branches when feasible

5

Improve air circulation and avoid moisture accumulation

Recommended Mauget Products

Fungisol

Professional-grade treatment specifically effective against cytospora canker.

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