Bacterial spot has been observed on pepper during the past several weeks. This disease, caused by the bacterium Xanthomonas campestris pv. vesicatoria, is favored by warm and humid conditions. The disease organism can be spread by rain or during overhead irrigation.
Leaf spots on affected leaves are at first small, yellow- green lesions with a water-soaked border. These spots may coalesce, giving a blighted appearance. Eventually these spots turn brown and dry up, leaving holes in the leaves. A tattered appearance of the leaves often results. Fruit spots are raised, scabby areas. Fungi may enter these spots and cause secondary fruit rots.
Bacterial spot is difficult to control once it is present. The following recommendations will aid in control:
- Use only inspected, healthy transplants.
- Avoid working around plants when the foliage is wet.
- Do not plant peppers or tomatoes in the same spot in successive years.
- Control weeds, especially nightshade and ground cherry. (The bacterium has been shown to survive on these solanaceous weeds.) Applications of a fixed-copper fungicide can slow the spread of the disease but will not eradicate existing infections. Remove infected plant debris or plow under deeply.
This article originally appeared in the July 22, 1994 issue, p. 118.