Holcus Leaf Spot of Corn
Published: 03/19/2019
Holcus leaf spot is caused by the bacteria Pseudomonas syringae pv. syringae. Holcus leaf spot usually does not cause major losses. Leaf spots are initially oval to irregular, dark green, water-soaked at the margins, and may have a light brown border. Later, lesions dry out and turn light tan, usually without a border. The dry lesions have a papery texture.
Holcus leaf spot often follows warm (77-86°F), rainy weather early in the season.
Holcus leaf spot lesions with water soaked edges.
Image: D. Mueller
Holcus leaf spot lesions may have a light brown border.
Image: A. Robertson
Most hybrids have adequate resistance. Other management practices are rarely warranted and fungicides are not effective against this bacterial disease.
Holcus leaf spot lesions may have a light brown border.
Water-soaking surrounding Holcus leaf spot lesions.
Gallery Images: K. Wise, D. Mueller, and A. Robertson
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.
