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Cytospora Canker Treatment Guide

cytospora canker disease on tree

Cytospora canker is a tree disease characterized by yellow, orange or black discolouration on the bark. The gummy ooze and cankers that develop can overtake your trees, making them unsightly and ultimately killing them. Once it appears, this persistent condition can be a handful to manage. Here’s a helpful guide to the identification and treatment of cytospora canker in your trees.

What is Cytospora Canker?

You should be aware of cytospora disease if you have aspen, cottonwood, poplars, apple trees, birch, willow, mountain ash, silver maples, spruce or Siberian elm on your property. It’s characterized by sunken cankers, often with a thick layer of resin, appearing on tree branches. If left untreated for multiple years, a canker can completely girdle its host branch, eventually killing the tree and potentially spreading to others.

Caused by various species of the fungus called Leucostoma kunzei, cytospora disease can affect many types of conifers. The fungus may be present in your healthy trees without causing harm, but stressors like insects, extreme weather conditions and other types of damage can weaken a tree’s resistance and make it susceptible to the fungus. The disease especially affects trees with roots damaged by construction or excavation.

Signs and Symptoms of Cytospora Canker

You should check your trees for cytospora disease once a year. Besides the unsightly swollen gall-like structures that can overtake your tree branches, there are more subtle signs you can catch early in the disease’s life cycle. Here’s a quick guide to checking for cytospora canker on your trees.

  • Pay particular attention to trees that are more than 15 years old.
  • Check for the presence of resin at the base of dead twigs and branches. The resin is a sign of cankers.
  • Look for dark blemishes on the tree branches. In wet weather, they’ll release yellow-coloured spore tendrils.
  • If you see diseased bark, remove it to determine whether the wood underneath is dead.
  • If you observe visible cankers, check for resin seepage. You may see an oozing liquid or white spots of dry resin.

The appearance of resin without the presence of swollen cankers may indicate a condition or infestation other than cytospora disease. To be certain of what you’re dealing with, a professional arborist can inspect and treat your trees.

Cytospora Disease Cycle

The fungus that causes cytospora cankers attacks the weakened portion of a tree. The cankers form in the living bark and wood and eventually envelop the branch until the host dies. It isn’t limited to a single season. It can attack in the fall, winter or spring when the tree is dormant and has fewer resources to defend itself.

Some types of cytospora can spread across different tree species, but others are host specific. If you’re planting new trees, talk to an arborist about strategic placement to minimize your risk of disease spread.

How to Treat and Control Cytospora Canker

Canker disease usually occurs on a weakened host, so the primary method of control is to prevent stress on the trees. Keep trees watered during times of arid weather conditions. Fertilizing and mulching help build up your trees’ resistance to infection, and careful pruning eliminates vulnerabilities on the trunk and limbs. Pay extra attention to trees that have recently been transplanted.

Avoid subjecting your trees to unnecessary stresses. Take caution with lawnmowers and weed trimmers not to damage the bark. If you spot signs of increased insect activity, take quick action to eliminate infestations.

You can’t cure cytospora canker with fungicides. If your trees are already infected, pruning is an effective way to treat and stop the spread of cytospora canker. During dry weather, use disinfected tools to remove affected branches and destroy them. You may have to do these prunings two years in a row to successfully stop the disease from spreading.

Treatment and Prevention of Tree Diseases in Western Canada

Make ArborCare® your first call for tree care, whether your trees are healthy, diseased or not yet planted. We provide tree planting, pruning and removal services on residential and commercial landscapes in Calgary, Edmonton and Winnipeg. Contact us today to arrange for an onsite inspection.

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