Septoria Brown Spot of Soybean
Published: 03/19/2019
Septoria brown spot is caused by the fungus Septoria glycines. It is the most common foliar disease of soybean. Disease develops soon after planting and is usually present throughout the growing season. Symptoms are typically mild during vegetative growth stages of the crop and progress upward from lower leaves during grain fill. Infected young plants have purple lesions on the unifoliate leaves. Lesions on later leaves are small, irregularly shaped, dark brown, and are found on both leaf surfaces. Adjacent lesions can grow together and form larger, irregularly shaped blotches. Infected leaves quickly turn yellow and drop. Disease starts in the lower canopy and, if favorable conditions continue, will progress to the upper canopy. Yield losses depend on how far up the canopy the disease progresses during grain fill.
Septoria brown spot lesions on soybean leaves.
Image: C. Grau
Septoria brown spot lesions.
Image: A. Robertson
Septoria brown spot disease cycle.
The fungus survives on infected leaf and stem residue. Warm, wet weather favors disease development. Disease usually stops developing during hot, dry weather but may become active again near maturity or when conditions are more favorable.
There are no known sources of resistance, but differences in susceptibility occur among soybean varieties. The host range of the pathogen includes some other legume species and common weeds such as velvetleaf. Rotation to non-host crops such as alfalfa, corn, and small grains and incorporation of infested crop residue into the soil will reduce survival of S. glycines. Foliar fungicides labeled for Septoria brown spot control are available. Applications made during R3 through R5 soybean growth stages may slow the rate of disease development into the middle and upper canopy and protect yield.
Early symptoms of Septoria brown spot on unifoliate leaf.
Septoria brown spot lesions on soybean leaves.
Yield losses depend on how far up the canopy Septoria brown spot lesions progress.
Septoria brown spot lesions beginning to grow together.
Septoria brown spot lesions can grow together and form large, irregular blotches on leaves.
Soybean varieties differ in susceptibility to Septoria brown spot.
Unifoliate leaf with Septoria brown spot lesions.
Early symptoms of Septoria brown spot.
Septoria brown spot causes leaves to turn yellow and drop.
Gallery Images: A. Robertson, C. Bradley, D. Mueller, A. Sisson, 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, gender identity (including gender expression), sexual orientation, 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 responsible Agency or USDA's TARGET Center at (202) 720-2600 (voice and TTY) or contact USDA through the Federal Relay Service at (800) 877-8339. 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, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: program.intake@usda.gov.
USDA is an equal opportunity provider, employer, and lender.
©2024 by the Crop Protection Network. All rights reserved.
