Cotton is an important cash crop worldwide. Bacterial blight, a disease caused by the bacteria Xanthomonas citri subsp. Malvacearum, can cause significant yield losses in cotton. The disease affects the plant’s leaves, stems, and bolls, causing wilting, chlorosis, necrosis, and ultimately death. To manage this disease, it is important to understand how it progresses.
Transmission of the disease
The bacterium is spread by wind, rain, insects, and contaminated equipment. Once it enters the plant, it multiplies and moves systemically with the help of water and nutrients. The infection starts in older leaves and eventually moves towards younger ones. The bacterium can survive in soil for less than five months.
Control measures
Control of bacterial blight in cotton requires an integrated approach that involves cultural, biological, and chemical methods.
Cultural control measures
Cultural methods include practices that reduce the spread of the bacterium. They include:
– Selection of disease-resistant varieties: Choose varieties that are resistant to bacterial blight.
– Crop rotation: Avoid planting cotton in the same field year after year as this can lead to a buildup of the bacteria in the soil.
– Destruction of crop residues: Remove all plant debris from the previous crop to prevent bacteria from overwintering.
– Clean cultivation: Keep the field free of weeds to reduce the risk of bacterial blight spillover from host plants.
– Sanitation: Sterilize all equipment that will be used in the field, especially during harvesting, to prevent the spread of the pathogen.
Biological control measures
Biological control refers to the use of natural enemies to suppress the pathogens. There are a few beneficial microorganisms that can help reduce the spread of bacterial blight. They include:
– Rhizobium: This bacterium forms a symbiotic relationship with plants, fixing nitrogen and increasing resistance to bacterial blight.
– Ochrobactrum: This bacterium produces biologically active compounds that suppress the growth of Xanthomonas citri subsp. Malvacearum.
Chemical control measures
Chemical control measures often provide the most effective response. While there are no effective curative chemicals, the following preventive measures can help control bacterial blight in cotton:
– Copper-based fungicides: Copper has been used for many years to control bacterial blight in cotton. It must be applied before infection to be effective.
– Bacteriophages: These are natural predators of the bacterium that causes bacterial blight in cotton.
Conclusion
Bacterial blight can cause significant damage to cotton crops. However, if proper disease management techniques are employed, the crop can be protected from significant yield losses. An integrated approach that combines a number of cultural, biological, and chemical methods is the best way to manage bacterial blight in cotton.