The Bacterial Diseases of the Bean 83 



methods of control, and, when employed with good cultural practices, 

 are satisfactory. Spraying and dusting are cumbersome, disagreeable, 

 and expensive processes even when they are effective, and the bacterial 

 blights of the bean are not of sufficient enphytotic character to warrant 

 their expense. That the expense would be considerable is certain. Nu- 

 merous applications would be necessary, since the bean plant is susceptible 

 to the blights at all periods in its life and also is a rapidly and almost 

 continuously growing plant. This would necessitate applications from 

 the seedling stage until the pods were mature. Furthermore, the bean- 

 blight problem in New York is not complicated with an insect problem 

 which frequently makes spraying or dusting necessary. One has only 

 the disease control to consider. Again, one must take into consideration 

 how much damage a spray machine would do to the bean plants. Such 

 varieties as Marrow, Medium, Pea, and Yellow Eye are of indeterminate 

 growth habits, and not only the vines, but the pods on them would be 

 destroyed. Even cultivators cause damage to beans, especially when 

 the plants reach the blossoming and podding stages, and it is one of the 

 better practices in bean culture to prepare the land so thoroughly that 

 few cultivations are necessary. 



How long the pathogenes will live in old bean vines in the fields is not 

 known. The ability of Phyt. phaseoli and Phyt. flaccumfaciens to live 

 for many years in a dry condition in leaves and seed, and of Phyt. phaseoli 

 to live for at least a year in the soil, shows that these two organisms are 

 rather resistant to their environment. A clean-up of old vines is desir- 

 able as a general sanitary measure, and probably would reduce chances 

 of infection where rotation of the bean crop is short. 



SUMMARY 



This memoir reports an investigation of the bacterial diseases of the 

 common bean (Phaseolus vulgaris). Six distinct diseases are recognized, 

 the causal organisms of which are as follows : Phytomonas phaseoli, Phyt. 

 flaccumfaciens, and Phyt. medicaginis var. phaseolicola, which have hitherto 

 been reported upon; and three newly described organisms, Phijt. phaseoli 

 var. fuscans, Phyt. vignae var. leguminophila, and Phyt. viridiflava. 



Careful and extensive inoculation experiments have proved the patho- 

 genicity of each organism. 



The symptoms of each disease on the bean plant are described in full 

 and their similarities and differences are noted. 



Various phases of the life history of the organisms are described. Phyt. 

 flaccumfaciens is primarily a vascular parasite; Phyt. phaseoli, Phyt. 

 phaseoli var. fuscans, and Phyt. medicaginis var. phaseolicola may or may 

 not be vascular parasites; Phyt. vignae var. leguminophila under certain 

 conditions may be found in the xylem; but Phyt. viridiflava cannot be 

 considered a vascular parasite. 



