1006 Walter H. Burkholdek 



the writer has observed a distinct wilting of the plants. In these latter 

 cases all the leaves dropped and turned brown, and persisted on the plant. 

 The small pods withered and clung to the stem, while the older pods 

 matured a few small seeds. A condition similar to this has frequently- 

 been observed which is due to the bacterial blight caused by Bacterium 

 phaseoli E. F. Smith. Careful examination, however, may distinguish 

 between the two diseases. 



The general appearance of fields of beans affected with the dry root-rot 

 may vary. Whenever the disease occurs in a field, approximately 100 

 per cent of the plants show the symptoms. All the plants may appear 

 uniform (Plate LVI, 1); on the other hand, certain parts of the field fre- 

 quently are affected more severely than others, thus giving the appear- 

 ance that the disease occurs in limited areas. There are several possible 

 explanations for this spotted condition. One is that the soil conditions 

 are not uniform; a second is that frequently wireworms or other insects 

 attack the decaying roots and complete their destruction. 



SYMPTOMS OF OTHER ROOT DISEASES OF THE BEAN 



Two other root diseases of the bean in New York State might be con- 

 fused with the dry root-rot. They are the black root-rot, caused by 

 Thielavia basicola Zopf., and a blotch caused by Rhizoctonia. In the 

 greenhouse, species of Botrytis, Fusarium, and various other fungi attack 

 the young seedling at the surface of the ground or cause more or less 

 of a root disturbance. These fungi have seldom been observed in the 

 field. 



Black root-rot 



The black root-rot in New York State is local in its distribution. It has 

 been observed only along the southern edge of the dry-shell-bean district. 

 In its early stages this disease is scarcely distinguishable from the dry 

 root-rot. The discoloration of the taproot at times may appear to be 

 somewhat purple in contrast to the orange-red color produced by the dry 

 root-rot. Otherwise the two diseases are very similar. Later in the 

 season, coal-black lesions, which are very characteristic, appear on the 

 affected roots. These lesions may vary from small streaks to cankers 

 which encircle half the taproot and completely envelop many of the 

 lateral roots. Frequently during damp weather a frosty appearance may 



