crown gall

Disease of plants caused by the bacterium Agrobacterium tumefaciens. Thousands of plant species are susceptible, including especially rose, grape, pome and stone fruits (e.g., apples, peaches), shade and nut trees, many shrubs and vines, and perennial garden plants. Symptoms include roundish, rough-surfaced galls, several inches or more in diameter. At first cream-coloured or greenish, they later turn brown or black. As the disease progresses, affected plants lose vigour and may eventually die.

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