The Dry Root-Rot of the Bean 1007 



be noticed over the lesions and the diseased parts of the plants. This 

 is due to the large production of the so-called endoconidiophores belonging 

 to Thielavia basicola. Since this disease is often observed associated with 

 the dry root-rot, the two groups of symptoms may be found together. 



It has been the observation of the writer that the black root-rot occurs 

 more generally during the early part of the growing season, and at times 

 affects germination. Frequently plants affected with this disease may be 

 able to throw it off by the middle of August, and late infection causes 

 no serious injury to the root system. These two observations have been 

 further substantiated by the writer through inoculation experiments. 

 The symptom of the dry root-rot, on the other hand, is more evident 

 during the latter part of the season. 



Rhizoctonia blotch 



The Rhizoctonia blotch in New York State is of general distribution 



but has never been observed to cause any appreciable losses. Brick-red 



blotches are produced mainly on the taproot and on the bean stem near 



the surface of the ground. The lateral roots are seldom affected. The 



lesions caused by Rhizoctonia are sunken, and usually irregular but 



definite in outline. This is the most distinguishing characteristic of the 



disease, and as a rule readily separates it from the other root diseases 



of the bean. 



ETIOLOGY 



The dry root-rot disease of the bean is caused by the fungous pathogene 

 Fusarium martii phaseoli n. form. 



MORPHOLOGY 



The pathogene causing dry root-rot of the bean has the following 

 morphological characters: 



Macroconidia mostly 3-septate (44.5 x 5.1 n), 4-septate (50.09 x 5.3 n), 

 rarely 5-septate, of nearly even diameter throughout, more or less curved 

 near apex, with somewhat rounded or but slightly pointed apex, usually 

 apedicellate. Microconidia rare. Aerial mycelium in culture scanty and 

 usually white. Spores borne mostly in pseudopionnotes. Cultures 

 when mature from a lichen 2 and montpellier green (on synthetic agar 3 ) 



2 The colors are after Robert Ridgway's Color Standards and Color Nomenclature. 



3 Richard's solution with two per cent agar. 



