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CIRCULAR 74 7, U. S. DEPARTMENT OF AGRICULTURE 



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Anthracnose 



Anthracnose, caused by Colletotrichum grami- 

 nicolum (Ces.) G. W. Wils., is a fungus disease 

 that attacks several grasses and is common on 

 Sudan grass. Initial symptoms appear on the 

 basal leaves as small necrotic eye spots with 

 visible black bodies in the center of each (fig. 15). 

 These open structures are filled with large 

 numbers of conidia, which, being readily washed 

 and splashed about by rain and dew, account 

 for much secondary infection. Conidia are 

 hyaline, slightly curved, tapered, and nonseptate. 

 As the disease progresses, all leaves often become 

 infected. Individual lesions frequently coalesce, 

 and entire leaves wither and die. Anthracnose 

 appears about midsummer and develops rapidly 

 from that time on until plant maturity. The 

 disease is favored by periods of humid, hot 

 weather. 



■&m 



Nonparasitic Foliage Disorders 



Nonparasitic foliage disorders caused by hered- 

 itary factors occur on several grasses, especially 

 Sudan grass. The symptoms are commonly 

 confused with those caused by parasitic organ- 

 isms. Several such disorders on Sudan grass 

 are shown in figure 16. 



Figure 15. — Anthracnose 

 on Sudan grass. 



