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Crown Gall of Peach
Crown gall is caused by a bacterium, Agrobacterium tumefaciens, and affects peaches, nectarines, apricots, plums, cherries, apples, pears, and quince. Peach and Mazzard cherry rootstocks are especially susceptible. The disease is common in tree fruit nurseries and can occur in orchards.
Symptoms
Crown gall is readily recognized by wartlike swellings, or galls, on tree roots and crown. Occasionally, the galls may be seen aboveground on trunks or branches. Young galls are light in color and with age become dark and hard, 1/2 inch to 3 or 4 inches in diameter. When galls are numerous, or if located on major roots or the crown, they may disrupt the flow of water and nutrients. Trees show reduced growth, an unhealthy appearance, and possibly nutritional deficiency symptoms.
Disease cycle
The bacteria causing crown gall are distributed widely in numerous soils and can attack many different kinds of plants. Soil may become contaminated if planted with infected nursery stock. Bacteria entering the plant must do so through a wound. Wounds are commonly made during digging and tree-planting operations, by tillage equipment, and by injury from root-feeding insects and nematodes. Secondary galls may develop a considerable distance from the initial infection. These may be formed in the absence of the crown gall bacteria, apparently due to a tumor-inducing substance produced at the site of the original infection.
Disease management
Avoid planting infected stock or wounding trees at planting.