Canker in Trees and Tree-like Shrubs..Death?...Not Necessarily

Canker

I have seen canker in many plants, particularly my yoshino cherry which is slowly dying from shot hole, a fungal disease. She is gorgeous; yet, providing less shade every year as she loses leaves earlier and earlier. I can't prevent this unless I wish to apply a foliar fungicide to all leaves several times a year - not gonna happen.

Fungal or bacterial issues with plants will typically not take down a tree or mature shrub in short time, or at all. But, they can affect the overall health, blooming and branch structure of most plants.

Canker is not actually a malady, but rather a symptom of another infection, typically a fungal or bacteria issue. Often, cankers are so very obvious, particularly during hotter, more humid and wetter seasons, as the plant oozes liquid from the wounds. They appear as open sores such as one a human (not to be confused with our canker or cold sore) may experience on one's skin if left untreated.

Canker - Girdling

Often, they are so prolific they will girdle a branch or stem and render it useless, often falling from a major stem or collapsing on the outer shell of a shrub or the crown of a tree. They aren't that difficult to identify; however, unfortunately, often only after the fungus has done its harm.

There are some diseases, fungi and pathogens, and the occasional pest, that have, will or are on their way to destroying certain species of plants, but this is rare.

There are several factors which I find most critical to a plants vitality and perhaps survivability:

Placement: Is the plant receiving the right or wrong amount of sunlight - most plants will survive regardless, but may not thrive (or survive) or bloom if they are not capable of receiving the right amount of sunlight? Is the plant confined by other plants and/or structures such as border walls or foundations? 

Airflow: There are very few plants which don't benefit from good airflow. However; many people often plant and place trees and shrubs in spaces for which they don't belong - often choked off and left to their own demise.

Soil Composition/Drainage: Almost every plant in the world loves soil which retains nutrients while also allowing for ample drainage of water. I'm not speaking of the nutrient quality of the soil, but its textural composition. Overly damp soil, in and of itself, is not a reason for plant death, but root rot (asphyxiation) is. Extreme moisture confined under a low-lying canopy can trap and hold moisture which may promote the development or spread of fungi.

Pruning: And, then we trim or have a lawn service repeatedly trim many plants which would be more naturally attractive and healthier via planned and thoughtful pruning. Some plants are suited for such indiscriminate trimming while most others require more thoughtful attention and require less maintenance over time. Otherwise we encounter die-back, uglier plants and disease issues.

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Case-in-Point

On a property for which I have performed many pruning and other projects, a row of sasanquas and a few camellias (both, same plant genus) are experiencing canker. The row or cluster of shrubs lives in a narrow area tightly bordered by a fence and one side of the home. And, the lawn irrigation, which is set to run too often and too long, is reaching the base of the plants.

I am currently in the midst of a pruning project for this property with the following objectives:

• Lower the overall height of the shrubs without topping and therefore creating a much larger mess.
• Prune for health reasons, removing as many disease-affected branches as feasible.
• Do so while sanitizing pruning tools involving stems or branches suspect or diseased.
• Increase airflow throughout the entire cluster of shrubs.
• Raise canopies and adjust (lower) the reach and timing of the irrigation system which is keeping the area too moist.
• Prune for aesthetics where desired.

It may take months to realize the benefits of the pruning in regard to the plants' health, but I will provide a follow-up once the project is complete.

Winter is one of the best times of year to be working on such issues.