Pod and Stem Blight of Soybean
Published: 03/19/2019
Pod and stem blight is caused by the fungus Diaporthe sojae. Pod and stem blight is characterized by black, raised specks that appear in linear rows on mature soybean stems. These specks are fungal reproductive structures known as pycnidia. Pycnidia can also cover pods, but they may not follow the linear pattern seen on stems. These signs are most prevalent from R6 through R8.
Linear rows of pycnidia on soybean stem characteristic of pod and stem blight.
Image: D. Mueller
Pod and stem blight pycnidia on stem and pod.
Image: C. Grau
The fungal pathogens survive in infested residue and seed. Infection occurs when spores are splashed by rain onto plants in early vegetative growth stages. Pod and stem blight is favored by warm, humid weather when soybean plants are maturing. Also, disease is more severe if harvest is delayed.
Crop rotation and tillage will reduce survival of the causal pathogen. Foliar fungicide can protect quality of seeds if applied near R5, but yield may not be increased. Risk may be reduced by planting a later maturing variety for the region.
For more information see the Pod and Stem Blight and Phomopsis Seed Decay publication.
Linear rows of small, black pycnidia on soybean stem characteristic of pod and stem blight.
Linear rows of small, black pycnidia along soybean stems are indicative of pod and stem blight.
Stems affected by pod and stem blight may have visible black streaks or lines.
Linear rows of small, black pycnidia on soybean stem characteristic of pod and stem blight.
Pod and stem blight pycnidia on stem and pod.
Gallery Images: D. Mueller, K. Wise, A. Robertson, and C. Grau
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.
In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating based on race, color, national origin, religion, sex, disability, age, marital status, family/parental status, income derived from a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all bases apply to all programs). Remedies and complaint filing deadlines vary by program or incident.
Persons with disabilities who require alternative means of communication for program information (e.g., Braille, large print, audiotape, American Sign Language, etc.) should contact the State or local Agency that administers the program or contact USDA through the Telecommunications Relay Service at 711 (voice and TTY). Additionally, program information may be made available in languages other than English.
To file a program discrimination complaint, complete the USDA Program Discrimination Complaint Form, AD-3027, found online at How to File a Program Discrimination Complaint and at any USDA office or write a letter addressed to USDA and provide in the letter all of the information requested in the form. To request a copy of the complaint form, call (866) 632-9992. Submit your completed form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW, Mail Stop 9410, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: program.intake@usda.gov.
This work is supported by the Crop Protection and Pest Management Extension Implementation Program from the U.S. Department of Agriculture’s National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.
USDA is an equal opportunity provider, employer, and lender.
©2025 by the Crop Protection Network. All rights reserved.
