112 Mortier F. Barrus 



are usually more extensive and more irregular in outline than those of 

 anthracnose, and by the absence of spore masses. 



Rhizoctonia (Plate VII) often occurs on the pod, producing lesions which, 

 particularly when they are small, closely resemble anthracnose. This 

 fungus attacks only the pods lying in contact with the ground. The 

 lesion has a bay to auburn center, often with a dark-colored ring near 

 the margin surrounded by a ferruginous border. The lesions are more 

 extensive than those of anthracnose, however, and do not contain the 

 characteristic spore masses (Plate I). 



Sclerotinia libertiana Fuckel produces a disease characterized by a soft 

 brown rot and moldy appearance of the pod, followed by a shriveling and 

 drying, which can never be confused with anthracnose. This fungus 

 commonly produces rather large black sclerotia on the pods. 



On pods of certain varieties, rust (Plate VIII) sometimes occurs as 

 pustules containing a black mass of dusty spores. 



When immature pods are exposed to the hot sun — as is often the case 

 when the leaves are injured by blight or by other means, especially when 

 the plants are approaching maturity — the exposed surfaces become 

 discolored with brown specks, spots, or blotches, in some cases a little 

 sunken, which may be mistaken for blight but hardly for anthracnose. 

 MacMillan (1918) describes these lesions as he found them on certain 

 varieties of beans in Colorado and in the East, and the writer has observed 

 them commonly in the East on many varieties. A peculiar browning, 

 different from sun-scalcl, was also observed, but the cause was not deter- 

 mined. A browning of pods may occur from other causes also, none of 

 which, however, need be mistaken for anthracnose. 



ETIOLOGIC ASPECTS 



Name, classification, and synonymy of the causal organism 

 Bean anthracnose is known to be caused by the fungous parasite 

 Colletotrichum lindemuthianum (Sacc. & Magn.) Bri. & Cav., one of the 

 Melanconiales of the classification of Lindau (1900) as used in Engler 

 and Prantl's Die natiirliche Pflanzenfamilien. The fungus does not differ 

 appreciably in its morphological characters from a number of other species 

 belonging to this genus, nor, except for the presence of setae, from the 

 genus Gloeosporium. Not only are species of the genus Colletotrichum 



