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
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
COMMENTS on disease
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.
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
reduction is the key to prevent infection. Keep the trees as healthy as
trees from damage during home construction and utility repairs. .
trees during periods of summer drought with 1 inch of irrigation water per
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 .
not apply weed killers near the tree, especially beneath the limb canopy.
trees with slow-release tree and shrub fertilizer during early April.
and burn or dispose of any infected trees, and cut the remaining stumps flush
with the soil.