Butternut Canker and Others

Canker Diseases - Hardwoods

Butternut Canker

Butternut cankers

Cankers on butternut caused by Ophiognomonia (old name: Sirococcus) clavigignenti-juglandacerarum. Stem with bark (left) and with the bark removed (right) to show the cankered areas.

Butternut coalescing cankers

Many different cankers coalesce killing large parts of the stem and finally kill the tree.

butternut cross section

This cross section of a butternut tree shows cankers were produced for many years. At first only a few cankers were on the tree and the tree recovered. However, in later years the number of cankers and size of the cankers increased. Coalescing cankers kill butternut trees.

Butternut pycnidia

Pycnidia form on cankered stems producing conidia. No sexual state is known.


Black Knot of Cherry

Black knot year 1

A black knot caused by Apiosporina morbosa starting to form on a branch.

Black knot

Branches of cherry with black knot. 

Black knot

Perithecia are formed in the black stroma producing ascospores that cause new infections.

Old black knot on large tree

Main stem of cherry with black knot. Sometimes the black knot persists and grows larger as the tree grows.

 Black knot parasite

White fungal growth can sometimes be seen on the black galls. This is a mycoparasite called Trichothecium that attacks the black knot.


Diamond Willow

Diamond willow in field

Many perennial cankers on a willow.

Diamond willow

Willow stems with cankers

Diamond willow without bark

When the bark is removed from the cankered willow the diamond-shaped cankers can be seen.

Diamond willow walking stick

Diamond willow walking stick with many cankers all over it.


Cross section through a canker on willow showing 4 perennial cankers. The white regions are the only areas where the sapwood is still alive.


Golden Canker

Golden Canker

Canker caused by Aurantioporthe (old name: Cryptodiaporthe) corni on the main stem of alternate leaf dogwood. The canker has a bright golden coloration. The dark reddish bark is the natural color ofthe bark and the area not yet affected by the canker causing fungus.

Golden canker

Pycnidia and perithecia form on the cankered stems.

Golden canker pycnidia

Soon after the cankers form, pycnidia can be seen (raised bumps on the stem). The pycnidia will produce masses of asexual spores.