Diseases of pepper (
Bacterial leaf spot
Bacterial leaf spot of pepper is caused by Xanthomonas campestris pv. vesicatoria. This bacterium survives in crop debris in the soil and on seed. Disease develops only when there is plenty of moisture and warm temperatures (photo 1). During the summer monsoon or if plants are irrigated by overhead sprinklers, sufficient moisture may be present for infection when the bacteria are splashed or blown on to leaves (photo 2). Disease severity depends on the level of tolerance of pepper varieties to disease.
Symptoms often appear first in the lower canopy as water-soaked lesions. The center of the lesions may die out leaving spots that have a purple-brown border and a lighter brown center (photo 3). Although less common in Arizona, spotting on fruit is more damaging, creating raised, cracked spots that later may be sites for secondary infections.
Disease is less severe in well fertilized and irrigated plants. Applications of copper compounds such as copper hydroxide and copper sulfate are effective for disease control. Disease free seed should always be used for planting. Contaminated seed should be treated with a 40 minute soak of 20% bleach solution using one gallon of solution per pound of seed. Shake the seed continuously while soaking and dry promptly afterward.
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February 24, 2003