Hypoxylon Canker and Oaks

Hypoxylon Cankerhas been noted in the death of many oaks in the East Nashville   area over the last several years. This disease is not rare,  but due to the stressful droughts of the last several summers, a large number of trees are being affected.  The following is a description of hypoxylon canker in oak, taken from the Plant Disease Handbook:

dries. This dieback continues from branch to branch through the

stem until eventually the tree dies. This may require 1 or more years

 depending upon the environment and amount of stress experienced

by the tree. Near death or shortly after tree death the outer bark

sloughs off and exposes large masses of brown, dusty one-celled

spores (conidia). These spores are gone within a few weeks and a

grayish surface is visible. This is covered with numerous black

fruiting structures. Mature fruiting structures (perithecia) can

 forcibly discharge sexual spores (ascospores) for distances of 60 mm.

 They are then blown to surrounding trees where infection occurs

 again. Entry appears to be through injured surfaces on limbs or

trunk. The fungus grows best at 86 degrees F but can grow at 50

 and 100 degrees F.Hypoxylon canker causes a dark brown

discoloration of the sapwood. With age the infected wood is lighter

 in color and has black zones or patterns in the wood when observed

in cross section.Hypoxylon canker occurs primarily on trees which

 are or have been in stressed conditions. Trees which have been

damaged by excessive fill soil are often attacked by this organism.

It is also suspected to be a fungus that can invade on oak wilt-infected

 trees.

Control is achieved by maintaining the trees in a healthy condition.

Avoid injury to the trunk and limbs and never apply fill soil around

the trees. Chemical treatments would not be effective because the

fungus is located within the tree.”