Pythium Seed and Root Rot of Alfalfa
Pythium seed and root rot is caused by multiple oomycete (not a true fungus) species in the Pythium genus. This disease is primarily a seedling disease, causing rotted seeds, roots, and damping off. Seeds become a mass of soft, brown rotted tissue. Pre- and postemergence damping off occurs early in the season. The tissue of infected seedlings becomes soft, brown, and water-soaked before collapsing. Some seedlings survive in the right conditions by developing roots above infected root tissue. On older plants, root systems are reduced and general plant growth and development is inhibited.
Pythium spp. survive as oospores in crop debris and soil. Pythium seed and root rot development is favored by wet soils and cool temperatures. Conditions that slow seedling development favor Pythium seed and root rot.
Pythium seed and root rot can be managed by implementing a variety of cultural practices and the use of fungicide seed treatments. Cultural practices include improving soil drainage, maintaining appropriate soil fertility, planting when conditions favor seedling development, and making up for stand loss through higher seeding rates. Mefenoxam and metalaxyl fungicide seed treatments are effective against many Pythium spp.
Prepared and reviewed by the Alfalfa Pest Management Working Group.
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.
