Bacterial Blight of Soybean
Published: 01/25/2022
Bacterial blight is caused by Pseudomonas savastanoi pv. glycinea, and is usually one of the first foliar diseases to occur on soybean. Bacterial blight seldom causes serious yield loss. Symptoms usually begin in the upper canopy because young leaves are most susceptible. Small, angular, reddish-brown lesions are surrounded by a yellow halo. As the disease progresses, lesions often grow together to produce large, irregularly shaped dead areas. Centers of older lesions frequently fall out, causing leaves to appear tattered.
Bacterial blight leaf lesions.
Image: D. Mueller
Tattering of leaves occurs as bacterial blight lesions grow together.
Image: D. Mueller
Bacterial blight disease cycle.
The bacteria survive winters in crop residue and seed and are spread by rain and wind. Bacteria can survive on leaf surfaces during the season and infect plants when conditions are suitable. Infection occurs through stomates (natural leaf openings allowing air exchange) and wounds caused by wind, hail, etc. Thus, outbreaks are common after rainstorms with high winds. Cool temperatures favor bacterial blight; warmer temperatures will slow or stop disease development.
Crop rotation and tillage reduce survival of the bacteria. Non-hosts include alfalfa, corn, and small grains; other legume crops can be alternative hosts.
Black, spiny fruiting structures indicative of anthracnose leaf blight on dead tissue.
Anthracnose leaf blight leaf lesions.
Leaf lesions are oval or spindle shaped, tan or brown with dark brown or purple margins.
Corn seedling with anthracnose leaf blight leaf lesions.
Early in the season, lower leaves usually show anthracnose leaf blight symptoms first.
Leaf lesions are oval or spindle shaped, tan or brown with dark brown or purple margins.
This publication was developed by the Crop Protection Network, a multi-state and international collaboration of university/provincial extension specialists and public/ private professionals that provides unbiased, research-based information to farmers and agricultural personnel.
This information in this publication is only a guide, and the authors assume no liability for practices implemented based on this information. Reference to products in this publication is not intended to be an endorsement to the exclusion of others that may be similar. Individuals using such products assume responsibility for their use in accordance with current directions of the manufacturer.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD).
USDA is an equal opportunity provider and employer.
©2022 by the Crop Protection Network. All rights reserved.
