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Diseases on Cherry Trees

By Venice Kichura ; Updated September 21, 2017
Cherry trees fight several diseases.

Cherry trees are attractive fruit trees known for their delicious fruit, but they can be challenging to grow. Because they’re susceptible to various diseases and insect problems, they only live about 20 years, according to TreeHelp.com. When grown in poorly drained soil, cherry trees can develop several types of diseases. Although there’s no cure for many cherry tree diseases, the key to controlling them is detecting symptoms to prevent infections from spreading.

Cherry Leaf Spot

Cherry leaf spot is a fungal disease that generally affects foliage of sweet, tart and English Morello cherries, with tart cherries being the most vulnerable. Although the fungus that causes cherry leaf spot mostly bothers leaves, it can also affect stems and fruit. It’s first seen as small circular purple marks on the upper surfaces of leaves that eventually turn brown. Where there’s an abundance of spots they can form abnormal large patches. Because there are often spots remaining green, a leaf looks mottled. Older infected leaves appear yellow before dropping. A severe infection in early spring can prevent fruit from maturing. Control leaf spot by spraying with a fungicide in addition to raking and destroying infected leaves.

Black Knot

Black knot is easily detected by knots or hard black swellings on small branches. These knots, caused by spores releasing new infections during wet weather, ultimately girdle branches, killing them. New knots have an olive green color and appear around the time a cherry tree blooms. Control this disease by pruning knots that develop at blossom time. The North Dakota State University website recommends cutting 4 to 5 inches below a knot. It may be necessary to annually prune trees to properly control the disease.

Bacterial Canker

Bacterial canker attacks flower buds of a cherry tree just as they’re beginning to open. Symptoms of dark brown spots on leaves are similar to leaf spot disease. These spots can be angular or circular and are surrounded with a yellow coloration. Infected flowers will wilt, turn brown and die before they’re able to totally unfold. The dying flowers look like wet tissue paper wads with a brownish or grayish hue. Once this canker infection is established, it spreads to twigs and shoots. Cool wet weather after a cherry tree blooms can trigger an outbreak of bacterial canker. The disease can be spread by pruning tools, so good gardening hygiene is important. Preventative treatment involves spraying with a bactericide containing basic copper sulfate.