The Dry Root- Rot of the Bean 1015 



an extent as to cause immediate infection of bean seedlings. This, how- 

 ever, might be due to the mycelium. 



From observations it appears that as a rule the fungus is disseminated 

 in the manure used to fertilize the bean fields. It is the practice of 

 growers to pull the bean plants in the late summer, and, after threshing 

 the seed, to use the remainder of the plant as bean straw. This is fed 

 to cattle and sheep and is one of the valuable by-products of the bean 

 industry. The straw contains the diseased bean roots, which are seldom 

 eaten but are thrown into the compost heap where they undergo further 

 decomposition. The fungus here lives saprophytically and produces its 

 spores on old bean roots and stems. When the manure is spread over 

 the fields the pathogene also is carried to new areas. A striking instance 

 of this was observed on a farm near Perry, New York. During the latter 

 part of the growing season of 1916, the location could be determined 

 where four loads of manure had been distributed in the bean field. This 

 was due to the fact that the dry root-rot was more severe in these places. 



In the sections where snap beans are grown, this method of dissemina- 

 tion of the fungus does not apply. Here, after the crop is harvested, the 

 vines are plowed under, not pulled for straw. Thus the fungus does not 

 get into the manure, and therefore is not distributed so readily over 

 the fields. 



The pathogene may be carried from one field to another in various 

 other ways. It may be disseminated on the feet of horses and of men, 

 and on tillage instruments. It may be spread by the wind, blowing 

 dust from field to field. Observations in the greenhouse indicate that 

 it can be carried by insects. Another means of dissemination is by wash- 

 ing. In the valleys about Warsaw and Attica, New York, all the fields 

 are equally contaminated with F. martii phaseoli, whether or not they 

 nave been planted to beans or have had bean-straw manure applied to 

 them. It is known, however, that in certain years these fields have 

 been under water during the early spring. At such periods it is very 

 probable that the pathogene is carried from field to field along the valleys. 



There are no indications that the fungus is carried with the seed, 

 although if the seed is not well cleaned it may harbor small pieces of the 

 diseased roots and particles of dirt containing the pathogene. 



The dry root-rot fungus may overwinter in the bean straw or in the 

 compost heap, and in the following spring it is returned to the fields. 



