Diagnosing Plant Diseases – Part II of IV– Trunk, Branch, and Stem
 (Read 100+ times)
By Agnes Farside
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In Part I of Diagnosing Plant Diseases, I covered a few diseases that can be identified from observing plant leaves. Although it was not an exhaustive list, it covered the more common diseases found in the area I live, the Midwest. Part II covers diseases, hosts, symptoms, and controls found through the observation of plant trunks, branches, and stems or twigs. (This is not an exhaustive list.)
Cankers
Stressed trees and shrubs can be susceptible to Cankers, which is a dead area in the bark or cambium (a thin layer between the xylem and phloem). A gardener can identify a Canker by its sunken or flattened area in the trunk, branch or stem, or a discoloration around the surrounding area. They can grow and girdle the twig or branch, cutting off water and nutrient supplies, killing the tissue beyond. Canker pathogens usually enter a plant through an open wound. To control plants diseased with Cankers, remove infected branches or stems, and fertilize and water the plant properly. There are no known chemicals to fight Canker disease.
Cytospora Canker
This fungus infects spruces, especially Colorado blue and Norway. Douglas fir, larch, hemlock, and balsam fir is also susceptible to Cytospora Canker. Girdling usually occurs at the base of the branch, next to the tree trunk. This fungus starts at the bottom and works its way up a plant. Inner bark infected by the Canker may be brown in color. It may take several years for a tree to die from this disease, as it moves slowly upward, killing one branch at a time. Wound sites and drought stressed trees are prone to this disease, so take special care not to wound the plant and to water it during dry spells. Remove dead branches during the winter months that have become infected. There are no known chemicals to fight Cytospora Canker.
Fire Blight
This bacterium infects 75 different species of plants such as pear, crabapple, blackberry, apple, and spirea, just to name a few. This disease starts at the top and works downward, spreading one to 12 inches per day. It infects blossoms, trunks, branches, and shoots. After a time, twigs will turn brown or black making the whole plant look as if it had been scorched. Control of the disease involves removing the infected branches during dormant periods by pruning six to 10 inches below the diseased area, planting in well-drained soil, and not using high nitrogen fertilizers.
Crown Gall
Crown Gall is another bacterium that invades over 100 species of plants such as willow, maple, rose, and raspberry, just to name a few. This bacterium enters through fresh wounds and appears as a small growth on the stem, crown, or root. If is often found at a graft or the soil line. Galls start out small and round, but as they age, they become rough and irregular shaped. They can grow to a very large size and weigh multiple pounds. Young plants can become stunted, may wilt, and eventually die, while older trees may survive but in a weakened condition. Remove and dispose of young plants and reframe from replanting in the same place for at least three years or longer. Avoid wounding the plant and keep control of insects.
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Author Bio Box: Agnes Farside
 http://www.associatedcontent.com/user/110407/agnes_farside.html
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