Artificial Intelligence
Bacterial bean blight
Bean bacterial disease, also known as bacterial leaf burn, is more severe than damage caused by summer beans.
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**Symptoms**: This disease primarily affects the leaves, but it can also damage stems and pods. On the leaf blades, the infection starts from the tips and edges, appearing initially as small dark green, water-soaked spots. As the disease progresses, these spots expand into irregular brown necrotic lesions with a yellow halo surrounding them. The affected areas become thin, transparent, and brittle, resembling burnt leaves—hence the name "leaf burn." Young leaves may shrink, deform, and fall off easily. Infected stems show water-soaked, brown streaks and often die within a week after being girdled. The fruits develop brownish-red, slightly sunken, near-circular spots. In severe cases, yellow-brown sunken lesions may appear on soybean seeds. Under wet conditions, yellow bacterial exudate oozes from the infected leaves, stems, and seed umbilicus. **Pathogen**: The causal agent is *Xanthomonas campestris pv. phaseoli*, a gram-negative bacterium. It is rod-shaped and possesses a single flagellum. The bacteria thrive at 30°C and are killed within 10 minutes at 50°C. **Disease Characteristics**: The pathogen can survive in the seed coat or within the seed for 2 to 3 years. Once the infected plant material rots, the bacteria lose their virulence. Infected seeds can lead to early seedling infections, causing pus formation at the growing point and cotyledon tissues. Wind, rain, and farm activities serve as transmission vectors. The bacteria enter through wounds or natural openings such as stomata. High temperature, high humidity, heavy fog, and condensation promote disease development. Conditions like sultry summer weather, continuous rainfall, and frequent irrigation accelerate the spread of the disease. Poor field management, excessive nitrogen fertilizer use, flooding, weed infestation, and pest problems also favor disease outbreak. **Prevention Methods**: 1. **Cultural Control**: Implement a three-year crop rotation. Plant in disease-free fields using certified disease-free seeds. Soak seeds in 55°C warm water for 10 minutes. Avoid overwatering with warm water. Apply well-rotted manure and remove infected plant debris. Use balanced fertilizers, increase phosphorus and potassium application, level the field properly to prevent waterlogging, remove diseased leaves early, and improve field ventilation. 2. **Chemical Control**: At the onset of symptoms, apply 14% copper oxychloride wettable powder diluted 300 times, 50% copper hydroxide DT wettable powder at 500 times, 77% copper WP at 500 times, or 72% streptomycin 4000 times. Also, use neomycin at 4000 times and 47% mancozeb WP at 1000 times. Spray every 7–10 days for 2–3 applications. These products can be alternated for better efficacy. Commonly used fungicides include copper oxychloride, copper citrate (DT), thiocarbamates, neomycin, and other bactericides.
**Symptoms**: This disease primarily affects the leaves, but it can also damage stems and pods. On the leaf blades, the infection starts from the tips and edges, appearing initially as small dark green, water-soaked spots. As the disease progresses, these spots expand into irregular brown necrotic lesions with a yellow halo surrounding them. The affected areas become thin, transparent, and brittle, resembling burnt leaves—hence the name "leaf burn." Young leaves may shrink, deform, and fall off easily. Infected stems show water-soaked, brown streaks and often die within a week after being girdled. The fruits develop brownish-red, slightly sunken, near-circular spots. In severe cases, yellow-brown sunken lesions may appear on soybean seeds. Under wet conditions, yellow bacterial exudate oozes from the infected leaves, stems, and seed umbilicus. **Pathogen**: The causal agent is *Xanthomonas campestris pv. phaseoli*, a gram-negative bacterium. It is rod-shaped and possesses a single flagellum. The bacteria thrive at 30°C and are killed within 10 minutes at 50°C. **Disease Characteristics**: The pathogen can survive in the seed coat or within the seed for 2 to 3 years. Once the infected plant material rots, the bacteria lose their virulence. Infected seeds can lead to early seedling infections, causing pus formation at the growing point and cotyledon tissues. Wind, rain, and farm activities serve as transmission vectors. The bacteria enter through wounds or natural openings such as stomata. High temperature, high humidity, heavy fog, and condensation promote disease development. Conditions like sultry summer weather, continuous rainfall, and frequent irrigation accelerate the spread of the disease. Poor field management, excessive nitrogen fertilizer use, flooding, weed infestation, and pest problems also favor disease outbreak. **Prevention Methods**: 1. **Cultural Control**: Implement a three-year crop rotation. Plant in disease-free fields using certified disease-free seeds. Soak seeds in 55°C warm water for 10 minutes. Avoid overwatering with warm water. Apply well-rotted manure and remove infected plant debris. Use balanced fertilizers, increase phosphorus and potassium application, level the field properly to prevent waterlogging, remove diseased leaves early, and improve field ventilation. 2. **Chemical Control**: At the onset of symptoms, apply 14% copper oxychloride wettable powder diluted 300 times, 50% copper hydroxide DT wettable powder at 500 times, 77% copper WP at 500 times, or 72% streptomycin 4000 times. Also, use neomycin at 4000 times and 47% mancozeb WP at 1000 times. Spray every 7–10 days for 2–3 applications. These products can be alternated for better efficacy. Commonly used fungicides include copper oxychloride, copper citrate (DT), thiocarbamates, neomycin, and other bactericides.
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