1016 Walter H. Burkholder 



This is a common method of hibernation, but it does not account for the 

 presence of the fungus in the majority of fields in the bean section of 

 New York State. The pathogene when it once gains entrance into a 

 field is very persistent, and may live for a number of years as a sapro- 

 phyte in the soil. Since the common practice in the bean section is a 

 three-years rotation, the fungus is known to exist for such a period in 

 the absence of the host plant. Observations indicate further that it may 

 live for as long a period as ten years. In the laboratory, in soil to which 

 no moisture was added, the pathogene died within a period of two years. 

 In addition to water, decaying organic matter is no doubt necessary for 

 the persistence of the pathogene in a saprophytic condition. 



Only one experiment has been conducted which has any bearing on 

 the length of time the pathogene may live in the soil under natural con- 

 ditions. This experiment was begun in 1915 and data, were taken at 

 the end of three years. Four rows of beans, approximately 100 feet 

 long, were inoculated with the fungus F. martii phaseoli. Four rows 

 were planted as a check to determine whether the pathogene was already 

 inhabiting the soil. The plants of the check rows remained healthy. 

 At the end of the season the bean plants were cut off and the roots were 

 allowed to remain in the soil. The plot was then dragged over and sown 

 to wheat and clover, both red clover and alsike (Trifolium pratense and 

 T. hybridum) being used in the seeding. After the wheat was cut in 

 1916, the clover remained on the plot until the spring of 1918, when the 

 plot was planted to potatoes. In October of 1918 soil was taken from 

 the plot where the diseased plants had been, and was placed in sixteen 

 pots in the greenhouse. Three seeds of the Red Kidney variety of beans 

 were placed in each pot. At the end of five weeks the roots of the plants 

 were examined. In no case were lesions of the dry root-rot observed 

 on them. The results of this experiment are contrary to all observations 

 of the writer in the field. Moreover, the test is small and inconclusive, 

 and is given here merely for what it is worth. 



In just what form the pathogene persists during the winter and in 

 the absence of its host plant has not been determined. It is probably 

 in the mycelial stage during favorable conditions and in the chlamydo- 

 spore stage during adverse conditions. Repeated examination of over- 

 wintered matter has never revealed the presence of a sexual stage. 



