Hypoxylon Canker Of Oak

Disease Information

Hypoxylon Canker

 This is a white-rot fungal disease primarily of oaks, and is caused by Biscogniauxiaatropunctata var. atropunctata (syn. Hypoxylonatropunctatum)Many species of oaks are susceptible to this disease

Symptoms and damage

As the fungus spreads and forms cankers, the first symptom that may be observed is the dying back of the crown (top) of the infected tree. However, other tree problems may also result in dieback.  Subsequently, the outer bark begins to slough off in areas of infection, and pieces of bark can be seen at the base of the tree. This bark loss exposes the first sign of the fungus, which is a brownish fungal stroma where conidia (or asexual spores) of the pathogen are produced. This area may be several inches to several feet long on limbs and trunks. These conidia are wind-disseminated and can cause new infections on other trees.

COMMENTS on disease

As the infection continues to develop, the exposed area of fungal stroma changes to a gray or silver color, and finally to black as a second type of spore is produced. This is the sexual stage of the fungus, and these spores, which are also infectious, are spread by splashing rain or insects to nearby trees.


There are no controls for Hypoxylon canker on these hardwood trees once infection has begun on the trunk. If infection is observed on branches, these may be removed and burned, but there may be other infection sites that are not yet apparent on the tree.

Stress reduction is the key to prevent infection. Keep the trees as healthy as possible.

Protect trees from damage during home construction and utility repairs. .

Water trees during periods of summer drought with 1 inch of irrigation water per week.

Trees should be mulched with a 3-inch layer of organic mulch from the trunk to the dripline, but don`t pile mulch against the trunk. For more information on mulching trees .

Do not apply weed killers near the tree, especially beneath the limb canopy.

Fertilize trees with slow-release tree and shrub fertilizer during early April. 

Remove and burn or dispose of any infected trees, and cut the remaining stumps flush with the soil.


Share this article