Hypoxylon canker of shade trees
Hypoxylon infects trees throughout the United States, but a few notable wide-scale problems have occurred in Arkansas, North Texas, Oklahoma, and the Mountain West.
Fortunately, if Hypoxylon is found on the branches or limbs there is a good chance the tree will live if the fungus does not spread.
[5] Hypoxylon canker of shade trees has both an asexual (anamorph) and sexual (teleomorph) life cycle.
[1] If these spores land on a susceptible host, successful infection will take place if there are humid and warm conditions for 48 hours.
[7] After the conidia have been dispersed by late summer and fall, the stroma turn very dark, often brown or black, and crusty.
Within these perithecia fruiting bodies, the sexual spores—ascospores—are produced in and can also be distributed via rain splash and wind and infect in a manner similar to the conidia.
When damage or stress occurs, the fungi will further colonize, infect, and begin living off the nutrients of the tree, flourishing in the bark and vascular system.
[2] Natural stresses such as defoliation by insects, animal damage, soil nutrient depletions, drought, overcrowding, and other disease can weaken trees, enabling Hypoxylon to infect.
[10] Human-caused problems can also lead to infection; soil compaction and excavation, construction, and physical injuries are known stresses to trees.
Droughts account for a large majority of tree-related problems as the water deficit has a negative effect on the tree's natural developments.
As the wood further dries, the Hypoxylon fungi will feed and further white rot and decay of the tree will occur, potentially causing death.
[10] Although there is no known cure for Hypoxylon canker, proper management practices and care can significantly reduce problems that may occur.
Any major disruptions, such as landscaping or irrigation modifications, in the surrounding environment can develop significant problems for both young and mature trees.
Additionally, adequate propagation along with good drainage is extremely important in sustaining a healthy tree.
When dead or dying tree branches do appear, selective pruning should be performed to remove these potential infection sources.
[3] In 1972, the damage was significant enough to cause losses of $4 million worth of aspen across Wisconsin, Minnesota, and Michigan.
[3] Furthermore, severe drought conditions throughout the American West could exacerbate Hypoxylon damage to aspens since the fungus takes advantage of water stressed trees.
