The bacterial spot of tomato is a serious and widespread disease that affects tomato plants. It can have an impact on both the yield and marketability of the crop. This disease is caused by the bacterium Xanthomonas vesicatoria. It is particularly prevalent in warm and wet climates and greenhouses.
Bacterial spot of tomatoes is a concern for farmers and gardeners, particularly in regions such as Wisconsin, where the disease is frequently observed. The infection can cause leaf spots and fruit spots and can even lead to wilting and death of the plant if left uncontrolled. To mitigate the effects of bacterial spots, it is important to understand the disease, its causes, and methods of prevention and control.
Bacterial Spot Management in Tomato
The Causal Organism of Bacterial Spot
The bacterial spot of tomato is caused by various species of the bacterium Xanthomonas, including Xanthomonas vesicatoria, Xanthomonas euvesicatoria, Xanthomonas gardneri, and Xanthomonas perforans. These bacteria are highly contagious and can be easily spread through contaminated seeds and transplants, as well as through wounds on the plant.
The pathogens enter the plant through natural openings, such as stomates. They can quickly spread throughout the plant causing significant damage. Bacterial spots can cause yellow or brown circular leaf spots, fruit spots, and in severe cases, wilting and death of the plant.
The Disease Cycle of Bacterial Spot
The disease cycle of the bacterial spot of tomato starts with the survival of the bacteria from one season to the next in various sources such as crop debris, volunteer tomatoes, and weed hosts such as nightshade and groundcherry. The bacterium can also persist on seed and be introduced into a new growing area through contaminated seed or transplants.
Once introduced into a field or garden, the bacterium can spread rapidly through splashing water from rain or irrigation. The pathogen enters the plant through stomates or wounds. It can quickly spread throughout the plant causing significant damage. As the disease progresses, yellow or brown circular spots can develop on the leaves, spreading to other parts of the plant and causing wilting, death of the leaves, and reduced yield. The bacterium can also infect fruit, causing small, raised spots that can lead to unmarketable fruit.
Causes/conditions Favorable for Bacterial Spot Disease Spread in The Field.
The bacterial spot of tomato is favored by certain environmental conditions that promote the development and spread of the disease in the field. The following conditions are favorable for the spread of bacterial spot:
- Cool, wet weather: Development of the disease is promoted by cool, wet weather conditions with temperatures ranging from 70-80°F. This weather creates an ideal environment for the bacteria to thrive and spread.
- Mid-season: Infection is most common when the weather is cool and wet and the plant is actively growing.
- Rainstorms: Windy rainstorms can spread the disease as the bacteria can be easily splashed from one plant to another.
- Overhead irrigation: Overhead irrigation can also contribute to the spread of the disease by spreading the bacteria from one plant to another through splashing water.
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