2. Classification of disease based on symptoms (with one example of the following): Canker, Downy mildew, Mosaic
2. Classification of disease based on symptoms (with one example of the following): Canker, Downy mildew, Mosaic. Canker : Widely distributed throughout the United States, bacterial canker is most common on cherries and plums, but may also affect apricots and many other kinds of stone fruits. Suspect this plant disease if sunken, water-soaked or “gummy” lesions form on the trunk or twigs. When trees begin active growth in the spring, a sour smelling sap may ooze from these wounded areas. The cankers become darker than the surrounding healthy bark, and the underlying tissue is reddish-brown to black and moist. If cankers girdle the branches or trunk, the leaves above the diseased area curl and turn yellow. Growth stops and the branch or tree will eventually die. The bacterium that causes canker, Pseudomonas syringae , enters trees through injured bark or an existing wound, such as a pruning cut on a twig or branch. Frost damage in the spri...