Scientific Name(s)
Pseudomonas syringae
Leaf Condition
Interveinal Necrosis, Leaf Spot, Pustule
Leaf Color
Yellow, Interior Red Spots, Bleached, Black Irregular Spots, Patchy Yellow And Brown Areas
Leaf Location
Entire, Upper, Lower, Young
Pod Condition
Main Stem
Necrotic Spots
Petioles Condition
Distorted, Lesion
Field Distribution
Random, Low Areas, Localized Area
Prior Environmental
Rain, Thunderstorm, Cool Cloudy
Mid To Late Vegetative, Flowering, Pods Present
Cropping System
Soybean Followed By Soybean, Conventional Till, Reduced Till


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.


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 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 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


This factsheet was prepared by the NCSU Field Crops and Tobacco Pathology Lab in 2020.


Assistant Professor & Extension Specialist
Entomology & Plant Pathology
 This NC State FactSheet can be viewed and printed at
NC State Extension