Canker causing fungi may live as endophytes on susceptible host. An endophyte means the fungus is leaving on and/or in host tissue, but there are no signs of disease. If the plant comes under significant stress, dieback can occur.

Leaf death and twig dieback are some of the first symptoms of canker diseases. Cankers are usually found on branches but may infect trunks of young trees. The disease may be initially undetectable except by shaving the surface of a branch to reveal brown discoloration of bark and/or underlying sapwood. As cankers enlarge, oval, sunken areas may develop on branches.

Large cankers may girdle and kill branches and entire plants if they develop on the trunk or main stems of shrubs. Gum production (gummosis) is often associated with fungal and bacterial cankers of cherry. Resin is often associated with canker diseases of junipers. Fire blight is a bacterial disease that may cause cankers. Fire blight is usually observed on plants in the Rosaceae family. Early symptoms may include blossom blight during bloom, followed by the shoot blight phase and signature symptoms such as shoots killed rapidly in the shape of a 'shepherd's crook'. Water soaked cankers may be found on the trunk and branches of infected plants.

For fungal canker diseases, keep plants irrigated during dry periods and remove diseased branches. Remove heavily cankered plants entirely.

For fire blight, prune during dormancy to remove cankered branches. Use cultivars resistant to fire blight for apple, crabapple, and pear.

For chemical control recommendations, consult the Insect and Plant Disease Control Manual, UT Extension Publication 1690, found here. Please contact your local Extension office for specific pesticide recommendations.