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Bacterial spot

(Xanthomonas arboricola pv. pruni (Smith) Vauterin et al.

On leaves, lesions are small, tan to brown in color, eventually becoming necrotic, and usually surrounded by a yellow halo. There are often numerous lesions on a leaf and they tend to be restricted to areas between veins, which gives them an angular appearance. Lesions are eventually walled off and the center of the lesion drops out, giving the leaf a tattered or shot hole appearance (A). Severe foliar infections results in the yellowing of leaves and premature leaf drop. Bacteria from leaf infections move to the current year's twig growth, leading to canker formation. On fruit, the bacteria cause dark brown lesions or blemishes. Lesions often become sunken and the skin of the fruit cracks, causing deep pits that leave the fruit unmarketable (B, C).

Distribution

Most common in warm and wet climates; tends to be a greater problem in orchards with a history of disease. It is one of the most serious diseases in southeastern US peach production.

Similar Species

Captan spray injury, especially on some plum varieties.

Management

Primary fruit and leaf infection occur during rainy weather from bloom to one month after shuck split. During this period, regular applications of a bactericide are needed when disease pressure is high or when highly susceptible varieties are grown. The most effective way to manage bacterial spot is to avoid planting susceptible varieties such as Babygold 5 and Autumn Lady.

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