Bacterial spot occurs on peppers and tomatoes. Many of the disease features are similar for both crops. The focus of the information presented here is on pepper. Worldwide, 16.5 million metric tons (36 million tons) of peppers are grown for fresh consumption and for use in condiments. For many people in the U.S., the bell-shaped pepper fruit is the most familiar (Figure 1); however, non-bell-type peppers (Figure 2) are more widely grown.

Figure 1	Figure 2	Figure 3
Figure 4	Figure 5	Figure 6

Bacteria attack the foliage, stems, and fruit of peppers and tomatoes. On peppers, lesions may form on fruit, including the peduncle (Figure 3), but the major crop loss (Figure 4) results from shedding of blossoms and young, developing fruit. Fruit that remain are usually non-marketable because of poor quality. They may have lesions and are often misshapen and damaged from excessive exposure to the sun as a result of defoliation. This can result in sunscald on the fruit (Figure 5). Diseased leaves drop prematurely resulting in extensive defoliation. As newly emerging leaves become infected and defoliation of older, diseased leaves continues, plants possess leaves mostly on their upper stems (Figure 6). Generally, defoliation is more common for peppers than for tomatoes. Because the diseased foliage often remains on tomato plants, affected plants may have a scorched appearance (Figure 7).

Figure 7	Figure 8	Figure 9

Leaves
Because the most obvious symptoms occur on leaves, the disease is often referred to as "bacterial leaf spot." Symptoms begin as small, yellow-green lesions on young leaves which usually appear deformed and twisted (Figure 8), or as dark, water soaked, greasy-appearing lesions on older foliage (Figure 9). Lesions develop rapidly to a size of 0.25 to 0.5 cm (0.1 to 0.2 in.) wide and become tan to brownish-red. Lesion shape is defined by leaf veinlets, so the shape is angular rather than the round shape that is more typical of fungal leaf spots or injury caused by some pesticides or other chemical sprays.

Lesions often are more numerous at the tip and margin of the leaf where moisture such as dew is retained (Figure 10). Under dry conditions, diseased leaves can develop a tattered appearance as the leaf margin and lesion centers become necrotic, dry up and disintegrate. Lesion size is often larger and symptoms are more severe when extended periods (> 12 hours) of moisture-saturated tissue occur.

Figure 10	Figure 3	Figure 11

Fruit
Fruit spots (up to 0.5 cm, 0.2 in.) begin as pale-green, water-soaked areas, which eventually become raised, brown, and roughened on pepper (Figure 3) and tomato (Figure 11) fruit. Spots may provide entrance points for various fungal and other bacterial invaders that can cause secondary fruit rots. The bacterial spot pathogen alone does not cause fruit rot.

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by The American Phytopathological Society