This article is about the plant disease. For the human condition, see mouth ulcer.

Canker and anthracnose are general terms for a large number of different plant diseases, characterised by broadly similar symptoms, the appearance of small areas of dead tissue, which grow slowly, often over a period of years. Some are of only minor consequence, but others are ultimately lethal, and of major economic importance in agriculture and horticulture. Different cankers and anthracnoses are caused by a wide range of organisms, including fungi, bacteria, mycoplasmas and viruses. The majority of canker-causing organisms are tied obligately to a single host species or genus, but a few will attack a wider range of plants.

Some cankers are treatable with fungicides or bactericides , but many are not; often the only treatment available is to destroy the infected plant in order to prevent the disease from spreading to other plants.

Some cankers:

• Apple canker, caused by the fungus Nectria galligena
• Ash bacterial canker, caused by the bacterium Pseudomonas syringae
• Butternut canker, caused by the fungus Sirococcus clavigigenti-juglandacearum
• Citrus canker, caused by the bacterium Xanthomonas citri
• Cypress canker, caused by the fungus Seridium cardinale
• Dogwood anthracnose, caused by the fungus Discula destructiva
• Grape canker, caused by the fungus Eutypa lata
• Honey locust canker, caused by the fungus Thyronectria austro-americana
• Mulberry canker, caused by the fungus Gibberella baccata
• Pine pitch canker, caused by the fungus Fusarium pini
• Plane anthracnose, caused by the fungus Apiognomonia veneta
• Poplar canker, caused by the bacterium Xanthomonas populi
• Rose cankers, caused by the fungi Leptosphaeria coniothyrium and Cryptosporella umbrina
• Willow anthracnose, caused by the fungus Marssonina salicicola