Leptosphaerulina Leaf Spot of Alfalfa
Leptosphaerulina leaf spot is caused by the fungus Leptosphaerulina briosiana. It is also known as Lepto leaf spot, and is among the most common foliar diseases of alfalfa. Symptoms are most often observed on new leaves as small, dark lesions or “pepper spots.” Lesions can increase in size to “eyespots” and are oval and brown with dark margins and yellow halos. Lesions form parallel to leaf veins, coalescing and causing leaf drop when conditions favor disease. Infection may also occur on older leaves and petioles.
Leptosphaerulina leaf spot leaf lesions.
Deborah Samac
Leptosphaerulina leaf spot can cause defoliation of alfalfa plants.
Deborah Samac
Leptosphaerulina leaf spot is favored by cool, wet weather. The fungus survives on infected leaf debris and spreads to newly developing leaves. Disease risk is higher during spring, early summer, and fall in the northern United States and is considered a midwinter issue in the southern United States.
A few cultivars have low levels of resistance. Ensure timely harvest; consider early harvest if Leptosphaerulina leaf spot is severe. Fungicides are registered for Leptosphaerulina leaf spot, but must be applied before symptoms are observed.
Foliar Fungicide Use in Alfalfa
Prepared and reviewed by the Alfalfa Pest Management Working Group.
Leptosphaerulina leaf spot leaf lesions.
Leptosphaerulina leaf spot can cause defoliation of alfalfa plants.
Alfalfa plants with Leptosphaerulina leaf spot.
Leptosphaerulina leaf spot leaf lesions.
Leptosphaerulina leaf spot leaf lesions.
Leptosphaerulina leaf spot can cause defoliation of alfalfa plants.
Gallery images courtesy Deborah Samac.
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.
