Gardening Guide: Cytospora Canker On Apricot Trees

Apricot tree have cankerous lesions which drip sticky gum and have orange curls? Information about cytospora canker, causes and treatments.

What Is It?

Cytospora canker is a plant disease that attacks apricots. Cytospora canker is also known as perennial canker. This plant disease is caused by one of two fungi which are related to each other. The first fungi that can cause cytospora canker is valsa cincta. The second fungi that can cause cytopsora canker is cytospora leucostomoa. Both of these fungi also attack plum, peach and cherry trees as well as do damage to apricots.

What Does It Look Like?

Cytospora canker in apricots starts with oval or oblong lesions which are on the bark of the tree. Usually these lesions present as being sunken on the bark and they enlarge slowly to form larger oblong areas of infection. Often, the lesions on the apricot tree bark will ooze a sticky or gummy material from the cytospora canker infection. Sometimes this gum is followed by the appearance of orange threads which tend to be thin and curly in appearance. As the cytospora canker progresses in the apricot tree, the bark will develop black freckles which appear along the edges of the initial lesions. Once the apricot tree leaves become infected, they will begin to wilt and may turn brown and die as the infection spreads. Eventually, if left untreated cytospora canker can kill off an entire apricot tree branch, and even an entire tree in extreme cases of cytospora caker.

How Does It Manifest?

Cytospora canker manifests from spread of either the valsa cincta or cytospora leucostomoa fungi which overwinters on dead wood. The curly orange threads mentioned in the decription of what cytospora canker looks like are fungal chains, and they most often form in the spring when the over wintered lesions release spores. Spores are spread by rain and wind and easily transmit fungi from an unhealthy section of an apricot tree to a healthy section, or from one apricot tree to another apricot, cherry, plum or peach tree. Infection sets up in injured tissues which can happen from mechanical wounds to the bark such as pruning, or from wounds in the apricot tree bark causes by cold temperatures or sunscald. As the fungus spreads and begins to decay the lesions appear on the apricot tree bark and become depressed, sunken looking cankers which start to ooze the sticky, gummy material which later turns into the orange fungal chains. Wet weather causes rampant spread of cytospora canker, and the fungal infection spreads most in weather that is between 70° and 85° F.



What Can I Do About It?

Unfortunately, there is no single control for cytospora canker in apricot, plum, peach or cherry trees. Usually a combination of measures is most effective in controlling the spread of cytopsora canker in your fruit trees. The first things to do is carefully remove infected branches which show signs of cytospora damage such as lesions, cankers and orange fungal threads. If you don't want to lose an entire branch, often cutting out the offending canker from the bark is effective. You will need to then paint the cut areas of apricot tree trunk with a latex paint. Using white paint is double effective because it not only prevents the fruit tree from becoming infected through the pruning wound, but also protects against cold injury and sunburn.

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