Nov. 15. I9I9 Bacterial Blight of Soybean 191 



of doors typical lesions usually began to develop in about 10 days after 

 the inoculum was applied. 



Only one attempt was made to inoculate pods. This experiment was 

 performed in the field in September, 191 7, when young pods were simply 

 sprayed with a water suspension of strain A. Typical lesions developed 

 in almost every pod, whereas the controls remained absolutely free 

 from spots (Pi. 13, B). 



RELATIONS TO HOST TISSUE 



Razor sections of lesions in fresh leaves show the bacterial invasion to 

 be in the parenchymatous tissue. Critical histological studies have not 

 been made, but leaf lesions fixed in Gilson's fixative, embedded in par- 

 affin, sectioned, and stained in carbol fuchsin have shown intercellular 

 invasion. Infection evidently takes place through the stomata. 



OVERWINTERING, DISSEMINATION, AND CONTROL 



Practically no experimental work has been done up to this time con- 

 cerning the bacterial blight organism in relation to overwintering and 

 dissemination. It has been noted, however, that the disease appears 

 year after year in the same field and also that it may appear almost as 

 soon as the first leaves have developed, although it must be remembered 

 that this latter condition is not at all universal and that the lesions 

 sometimes make their first appearance when the plants are nearing 

 maturity. These facts seem to indicate that the organism may be 

 carried with the seed and also that it ma}^ live over in the soil. Pods 

 and seeds often become badly affected with the disease as we have 

 already seen and, although we have learned that the organism does not 

 withstand long periods of desiccation, at least in the leaves, there is a 

 possibility that it may live a much longer time upon the seed, or, judging 

 from the nature of the invasion, within it. 



Until further work on overwintering and dissemination has been 

 done it will be impossible to recommend any specific control measures 

 aiming to check the development and spread of the disease in the field. 

 Destroying all diseased plants, rotation, and the selection of sound 

 seed for planting have been suggested as possible means of control; but 

 it will be seen at once that the first recommendation is impracticable 

 from the standpoint of soybean culture; and, considering how generally 

 the disease occurs, we can not entertain very great hopes of the other 

 two iri practice. Considerable observational data have been accumu- 

 lated, however, during the last few years concerning varietal resistance 

 and susceptibility to the soybean blight, and there seems to be no ques- 

 tion that decided differences in varietal resistance exist. During the 

 last few seasons the writer has observed repeatedly, in variety test 

 plots, perfectly healthy plants growing immediately adjacent to others 



