Bacterial spot is a disease that affects both tomatoes and peppers. It is a microbial, waterborne bacterium that spreads rapidly from plant to plant. It can affect not only growing plants but peppers and their seeds as well. Bacterial spot can become serious if left untreated. Wild plants such as nightshade and ground cherry can host the disease.
One cause of a bacterial spot outbreak in peppers is that the disease is capable of overwintering in decaying vegetation for a year. The next spring when the rains begin, the organism begins multiplying and--through touch, wind and splashing--can be transferred to other plants. The other cause of bacterial spot is infected seeds. The bacteria can survive dormant in a pepper seed until it reveals itself as lesions on the cotyledons or first pair of "seed leaves" emerges after planting.
Aside from the pepper plant's cotyledons having lesions, other symptoms of bacterial spot include numerous, angular spots on the pepper plant's leaves. As the spots first appear, they have a water-soaked look. If the leaves are young when the infection occurs, they become misshaped. The edge of the spot may be ringed with dead tissue. On the peppers themselves, the disease manifests as irregular blisters that later look more like warts.
If a pepper plant becomes badly infected with bacterial spot, the affected leaves begin to drop off. Without the leaves, the plant cannot perform photosynthesis as well. The fruit becomes more exposed to the sun, and danger of sun scald is increased. Secondary fruit rots and decreased volume are likely. In severe cases, the plant simply dies.
Treatment of Bacterial Spot
Once a bacterial spot outbreak has occurred, there is very little treatment that can be effectively applied. Copper-containing bactericides may reduce the development and spread of the disease, but many other factors play a part in the success of such treatment, such as the extent to which the disease has already spread, and weather. If started early, treatment every seven to 10 days may be beneficial.
A number of things are effective in preventing bacterial spot on peppers. Practice crop rotation. Use certified disease-free pepper seeds. Buy pepper transplants from a reliable source, and check plants carefully before buying. Avoid working with pants when they are wet, to minimize spread. Remove and destroy any vegetation left at the end of the growing season to eliminate a place for the bacteria to overwinter.