Introduction
Bacterial blight is a common disease in soybean that is common in cool, wet weather. This disease is usually mild and does not result in yield losses.
Pathogen
Pseudomonas syringae pv. glycinea is the causal agent of bacterial blight in soybean. This pathogen survives in crop residue and can be seed transmitted.
Host Range
Other legume hosts, like lima bean and snap beans, may be hosts to this bacterial pathogen.
Symptoms
Symptoms include light to dark brown necrotic regions that are vein-limited giving an angular appearance on the young leaves of the plant, often with chlorosis surrounding the necrotic region. Lesions may coalesce to form large, irregularly shaped lesions. Leaf veins may become affected and create necrotic areas resembling lightning on the leaf. Bacterial blight closely resembles brown spot (Septoria glycines), but can be distinguished by the lack of fungal structures in lesions, and the presence of large yellow halos around the lesions.
Disease Cycle and Conditions Favorable for Disease
Bacteria survive in crop debris or can be seed transmitted. The bacteria is splash dispersed to leaves during precipitation events. Leaf injuries (e.g. hail or wind injury) may increase the severity of damages observed. Disease is favored by cool, wet conditions and soybeans are susceptible throughout the growing season.
Management
Management is rarely needed for bacterial blight. Planting pathogen-free seed is important to reduce spread of bacterial blight. In fields with consistent damages, cultivation may help reduce survival of bacteria in crop debris.
Useful Resources
- The NC State University Plant Disease and Insect Clinic provides diagnostics and control recommendations.
- The NC State Extension Plant Pathology portal provides information on crop disease management.
- The North Carolina Agricultural Chemicals Manual provides pesticide information for common diseases of North Carolina. The manual recommendations do not replace those described on the pesticide label, and the label must be followed.
Acknowledgements
This factsheet was prepared by the NCSU Field Crops and Tobacco Pathology Lab in 2020.
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Publication date: Sept. 9, 2020
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