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HELMINTHOSPORIUM LEAF DISEASE OF LAWN GRASSES 



The U. of I. Plant Disease Clinic has recently received several specimens from home 

 lawns. The most common disease problem has been a leaf disease caused by a number of 

 species of the fungus Helminthosporium . The predominantly cool and wet spring this 

 year has favored the development of this disease in bluegrasses, fescues, ryegrasses, 

 bentgrasses, Bermudagrasses , and zoysia as well as in various wild and pasture grasses. 



The disease first appears as small, dark-brown lesions with purple to reddish-purple 

 margins. The centers of these lesions fade to an ash-white to light brown or straw 

 color, giving the spot an "eyespot" appearance. Under favorable conditions, these 

 spots rapidly increase in size. Two or more lesions may run together, girdle the 

 leaf, and kill the leaf blade. The girdling and subsequent death of the leaf may 

 cause a gradual browning and thinning effect in some lawns. Once established, the 

 Helminthosporium fungi present a continuous problem. 



The Helminthosporium leaf disease in grass can be controlled in a number of ways: 



1. Mow bluegrasses, fescues, and ryegrasses at the recommended height for satisfac- 

 tory turf use. Mow frequently, so that no more than a fourth to a third of the 

 grass surface is removed at one time. 



2. Remove any dense matting or thatch of dead grass (over a half inch deep) using a 

 vertical mower, power rake, or some other machine designed for this purpose. 



3. Apply a fertilizer that will supply nitrogen to the diseased turf, which will help 

 it recover more rapidly. 



4. Seed or sod resistant varieties. 



5. Where the shade is heavy and air movement is restricted, thin or remove dense 

 trees or shrubs . 



6. Apply a preventative chemical spray. Make the first application when the grass 

 begins to turn green. The second and third applications should follow the first 

 one by 2 and 4 weeks, respectively. Because these fungicides are protective in 

 their action, the entire leaf surface must be covered. To assure such coverage, 

 apply the spray under at least 25 pounds of pressure per square inch. 



The following turn fungicides are recommended for controlling Helminthosporium leaf 

 disease in lawn grasses: 



Acti-dione-Thiram Maneb, 801 WP 



Captan, 501 WP Tersan LSR 



Dyrene, 501 WP Zineb, 751 WP 



Folpet (phaltan) , 501 WP Daconil 2787, 751 WP 



Fore, 801 WP 



NOTE: Follow the manufacturer's directions carefully regarding dosage, timing of the 

 applications, safety, and other factors. DO NOT graze treated areas. DO NOT feed 

 clippings to livestock. 



More information about this disease is available in the Report on Plant Diseases No. 

 405 "Helminthosporium Leaf, Crown, and Root Diseases of Lawn Grasses." Copies are 

 available from the University of Illinois Department of Plant Pathology, 218 Mumford 

 Hall, Urbana, Illinois 61801. 



