Sooty Canker – A Leading Cause of Tree Dieback in Arizona
A fungus called sooty canker, also called branch wilt or limb wilt, is a disease that affects a variety of trees in the Arizona region. Trees that are especially susceptible are typically stressed or damaged.
Fungal spores can be transferred easily by wind or rain, especially during what’s considered the “mild wet weather in the winter months” in some parts of the state (University of Arizona, 2021). The fungus then grows into the bark and produces black masses of spores below the surface. Trees that have cracks and wounds from heat stress, sunburn, improper pruning or freezing are more likely to be attacked by this disease.
Signs to look for:
- Early stages may show brown staining on branches
- Black-stained or sooty areas on bark, branches and leaves
- Small, wilted leaves that die prematurely during warmer months
- Cracked or peeling bark that exposes black fungal spores
Preventive care is the key to maintaining tree vigor and helping trees stay resistant to this disease.
How to protect trees from sooty canker
According to Extension Plant Pathologist at the University of Arizona Mary W. Olsen, it has been found that sunburned bark is one of the most common ways that sooty canker can take hold of a tree. Unnecessary pruning or wounding can also expose an access point for a sooty canker infection to begin.
Hiring an expert to perform professional tree pruning can ensure that “limbs that shade the trunk and scaffold branches are not removed,” says Olsen.
Experimental treatments for dormant and non-dormant trees impacted by this fungus are still being studied and tested. While there is no known cure for sooty canker, keeping a close eye on your trees and having an arborist check on their health periodically is a great way to catch signs of the disease before it’s too late.
Olsen states that if the disease has only made a home in the upper branches, “removing infected limbs by cutting at least six inches below infection sites” can help to control sooty canker.
Expert arborists can carefully remove infected limbs to ensure that the tree is not left vulnerable with new cracks or wounds. This is typically done during cool, dry periods since the disease is more likely to progress during warmer weather.
