Hypoxylon Canker Disease on Oak and Shade Trees (Biscogniauxia Canker)

Keep your tree from becoming an extreme threat to your property and landscape when it is infected by Hypoxylon canker. When you know how to identify and treat this disease, you might save your tree.

toddsmariettatreeservices.com gathered information about the definition, identification, treatment, and prevention of Hypoxylon canker.

Hypoxylon Atropunctatum Disease Definition

Hypoxylon atropunctatum is the former, more widely-known name of Biscogniauxia canker or dieback. This disease is a frequent contributor to the decline, decay, and death in a wide range of tree species.

Biscogniauxia fungi are an opportunistic species that do not affect healthy, thriving trees. When a tree is under hydraulic (water), root disease, physical damage, or soil compaction induced stress, these fungi can quickly colonize the host tree.

Once the disease has colonized a tree and produces fruiting structures, it is a signal that the tree is in rapid decline, if not already dead. This is especially true when the infection is located in the trunk.

Hypoxylon canker disease with fruiting structures

Identification of Hypoxylon Canker Disease

The following symptoms are indicative of a tree in declining health that may signal the presence of Hypoxylon atropunctatum (Biscogniauxia canker):

• Chlorosis of the tree’s foliage
• Reduced twig growth and smaller leaf growth
• Dead or browned leaves remain attached
• Dead branches or limbs
• Thinning canopy
• Water sprouts growing from the trunk, large limbs, or roots
• White, decayed sapwood in cankered areas of the tree
• Patches of outer bark sloughing off of the branches or trunk

The following are signs to positively identify the fungus:

Early Growth Stages – Looking at cankered areas on a tree, you will see a dark red to brown or olive-green fungal tissue (stroma) over those areas.

Later Growth Stages – Flaking grey surface that reveals a brown to black crusty material with the impression that the area had burned.

Advanced Growth Stages – Small infected patches that eventually merge together to form strips of infected material along the trunk and limbs of the tree.

Hypoxylon canker disease damaging tree bark

As the fungus moves through the growth stages, sections of the infected tree’s bark will pop or fall off, revealing a fungal mat where the tree’s cambium should be.

The following tree species can serve as host to Hypoxylon canker disease:

• Quaking aspen (Populus tremuloides)
• Bigtooth aspen (Populus grandidentata)
• Black poplar hybrids (Populus nigra)
• Balsam poplar (Populus balsamifera)
• European aspen (Populus tremula)
• Violet Willow (Salix daphnoides)
• Eastern Cottonwood (Populus deltoides)
• White poplar (Populus alba)
• Southern Live Oak (Quercus virginiana)
• Red Oak (Quercus rubra)
• Blackjack Oak (Quercus marilandica)
• Post Oak (Quercus stellata)
• American sycamore (Platanus occidentalis)

Note: Hypoxylon canker has three primary species that can infect a variety of shade trees. Hypoxylon atropunctatum is commonly found on oak species, Hypoxylon mammatum attacks mostly aspen trees and Hypoxylon tinctor primarily infects sycamore trees. If none of the above trees and species are yours, these are other tree diseases and treatment instructions toddsmariettatreeservices.com/5-marietta-ga-tree-diseases-identification-treatment/

Treatment of Hypoxylon Canker Disease

There are no known fungicides that can prevent or cure Hypoxylon canker. It is important to remember the opportunistic trait of this fungus. When it can thrive on its host, that tree’s health is compromised or in decline. The following will help you chose an appropriate course of action:

Hypoxylon Canker on Limbs and Branches – When this disease has infected the limbs and branches (not the trunk) of a tree:

• Those limbs and branches should be carefully pruned from the tree.
• Prune infected limbs and branches in sections if needed to minimize disturbing infected areas.
• Wood infected by any species of fungi should be handled as highly transmissible to surrounding trees.
• Do not run these limbs and branches through a wood chipper.
• This wood can be burned.

Hypoxylon Canker on Tree Trunks – When this disease has infected the tree trunk, there is nothing you can do to prevent the decline and eventual death of the tree:

• Hire a professional tree service to carefully remove the tree.
• Do not run a Hypoxylon canker infected tree through a wood chipper.
• This wood can be burned.

Hypoxylon canker disease damaging tree trunk bark

Hypoxylon canker thriving on a tree is a clear indication that the tree was already in distress.

Prevention of Hypoxylon Canker Disease

Hypoxylon canker may already be present on your tree, waiting for the tree’s defenses to weaken. Some ways to prevent this disease from developing include:

• Remove any trees that have developed cankers on their trunks. As these trees die, they become an extreme hazard to property, people, and surrounding trees.
• Prune branches and limbs with cankers before they reach the trunk.
• If 25% of the tree’s crown will be lost from pruning, consult a professional tree service to evaluate the condition of the tree and recommend a course of action.
• Avoid planting poplar, willow, oak, and aspen near trees with Hypoxylon infections until those trees have been removed.
• Mulch your trees.
• Water your trees and provide frequent deep waterings during periods of extreme heat and drought.
• Perform annual soil tests and adjust your use of fertilizer to provide the appropriate nutrients for the tree.
• Seasonally prune your trees to promote new and healthy growth.
• Immediately treat any signs of insect infestations.

Prevention of Hypoxylon or Biscogniauxia canker can only be achieved by promoting the health of the tree. This approach allows the tree to employ its natural defenses to suppress the growth/development of this opportunistic fungus.