6O BEAN CULTURE 



Treatment. As with all rusts the treatment must 

 consist largely in preventing the plants from becom- 

 ing attacked. This may be done first by planting 

 strong seed and favoring the beans with such condi- 

 tions as rich soil that has not been contaminated 

 with the rust spores by previous cropping with 

 beans. Early spraying with fungicides will help pre- 

 vent the rust from getting a foothold upon the sur- 

 face of the plants. However, when the rust appears 

 in large amounts, the crop of leaves and stems 

 should be burned as soon as possible and the grow- 

 ing of beans upon that land omitted for a term of years. 

 Some varieties are less susceptible to the disease 

 than others and it is well to select the stronger 

 growing sorts. 



Bean leaf spot (Isariopsis griseola), another com- 

 mon fungous trouble of the bean, is quite different 

 from other diseases in that it is confined chiefly to the 

 foliage where it produces numerous spots, usually 

 small and angular, without any colored border. Hal- 

 sted says* the fungus itself forms a gray, moldy cov- 

 ering upon the under surface of the spot where the 

 spores are produced in vast numbers. He concludes 

 that, since the spore production is of a superficial 

 nature, the fungus is amenable to the ordinary 

 treatment for similar diseases. Thorough spraying, 

 therefore, with a good fungicide such as Bordeaux, 

 is here recommended. 



Bean leaf blotch (Cercospora cruenta) affects the 

 foliage. It is found frequently in various sections of 

 the United States. The fungus produces patches on 

 the leaves which become useless and fall away. The 

 spots have an angular appearance something similai 



*N J Bui 151. 



