Helminthosporium leaf spot

Title: Helminthosporium leafspot
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066845/00001
 Material Information
Title: Helminthosporium leafspot
Physical Description: Book
Creator: Elliot, M. L.
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: 20??
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00066845
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved by the source institution and holding location.

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'Helminthosporium' Leaf Spot

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IFAS Extension

'Helminthosporium' Leaf Spot-

M. L. Elliott and G. W. Simone2

'Helminthosporium' Leaf Spot

Pathogen(s): Bipolaris, Drechslera and Exserohilum spp. (previously classified as
Hi llihi, "\ ", ilni, fungi)

Turfgrasses Affected: All warm-season turfgrasses, but it is usually most serious on
bermudagrass. Different species of these fungal pathogens affect different species of turfgrass.

Occurrence: This disease includes a group of fungi that are active over a wide range of
temperatures. At any given time of the year, at least one species within this fungal group can
be isolated. Thus, diseases caused by these fungi can occur at any time of year. However, as a
general rule, the leaf spot disease occurs during mild, wet periods in fall through winter.
Again, these diseases occur most frequently on bermudagrass.

Symptoms/Signs: Leaf spot symptoms tend to vary with each pathogen/host pair from very
small (pinhead size), solid brown to purple color lesions or spots to expanded lesions with
bleached centers that girdle the leaf blade ( Plate 18 ). Severely infected leaves turn purple or
reddishcolor, giving the turf an overall purple cast. Severely infected leaves will eventually
wither and dry to a light tan color. Distinct patches or patterns to the disease are usually not
obvious. "Meltingoccurs under severe infections as turf areas thin and die. Lesions on stolons
are dark purple to black.

CREDITS: G. W. Simone

Plate 18. Example of 'Helminthosporium' Leaf Spot symptoms on bermudagrass.



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'Helminthosporium' Leaf Spot

Cultural Controls: Avoid excess nitrogen during potential disease development periods. The
nitrogen level must be balanced with potassium. In areas that are affected routinely by this
disease, increase the potassium level prior to the time the disease normally occurs. A ratio of
1:2 (N:K) would be recommended. Use slow-release potassium sources or apply quick-release
potassium sources more frequently.

Overuse of certain herbicides (MCPP, 2,4and dicamba) have been shown to enhance
'Helminthosporium' disease development on coolgrasses. Note if there is a correlation
between disease outbreaks and the use of certain pesticides. If a correlation is determined,
then avoid using that particular pesticide or treat preventively for 'Helminthosporium' disease
prior to the use of that pesticide.

Chemical Controls: azoxystrobin, chlorothalonil, iprodione, mancozeb, myclobutanil,
PCNB, propiconazole, trifloxystrobin, vinclozolin.

Mancozeb can be applied to a residential lawn only by a professional pesticide applicator.
Chlorothalonil and vinclozolin cannot be applied to a residential lawn, but it can be applied to
turfgrass in a business or industrial landscape.

Refer to "Turfgrass Disease Management" section of the Florida Lawn Handbook for
explanation of cultural and chemical controls.


1. This document is SS-PLP-09, a series of the Plant Pathology Department, Florida
Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of
Florida. This information is included in the Florida Lawn Handbook, SP-45. For a copy of
this handbook, request information on its purchase at your county extension office. First
published: May 1991. Revised: April 2001

2. M. L. Elliott, Associate Professor, Plant Pathology, Fort Lauderdale Research and
Education Center, and G. W. Simone, Emeritus Professor, Plant Pathology Department,
Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of
Florida, Gainesville, FL 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution
authorized to provide research, educational information and other services only to individuals and
institutions that function with non-discrimination with respect to race, creed, color, religion, age,
disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For
more information on obtaining other extension publications, contact your county Cooperative
Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida
A. & M. University Cooperative Extension Program, and Boards of County Commissioners
Cooperating. Larry Arrington, Dean.

'Helminthosporium' Leaf Spot

Copyright Information

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Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all
conventions, but permits free reproduction by all agents and offices of the Cooperative Extension
Service and the people of the State of Florida. Permission is granted to others to use these materials
in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the
publication, its source, and date of publication.

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