1923] 



LEHMAN — POD AND STEM BLIGHT OF SOYBEAN 165 



when the plants are 1 or 2 feet high and be repeated often enough 

 to keep the foliage covered. Because of the manifest similarity 

 between pod blight of lima bean and pod and stem blight of soy- 

 bean, it seems that spraying should reduce the losses from the 

 latter disease sufficiently to render the operation profitable. 

 Because of the difficulties encountered in spraying plants with 

 dense foliage, such as is found on soybeans, it is possible that 

 dusting with Bordeaux or sulphur might give more satisfactory 

 control because of better penetration of dense foliage by dust 

 than by spray. The coincidence of the time of most abundant 

 infections and the summer period of heavy rainfall is a factor of 

 considerable importance bearing on any spraying or dusting 

 schedule that may be proposed. The protective material must 

 be something that will stick to stems, pods, and leaves during 

 rainy weather. However, the hairy nature of pods and stems 

 would assist in maintaining the protective film on the plant 



parts. 

 Diseased seeds have yielded isolations of the causal fungus in 



April and May following the season in which they were grown. 

 In one case the fungus was isolated from seed obtained from 

 diseased plants 17^ months after harvest. These plants were 

 kept in the laboratory during the interval between harvest and 

 the time of making the isolation, and the seeds were disinfected 

 in alcoholic mercuric chloride and germinated on moist sterile 

 blotting-paper in large test-tubes. Thus it seems probable 

 that the fungus may remain viable even to the second planting 



season after haryest. 



The fact that the organism causing this disease penetrates the 

 seed-coats and passes the winter as an internal mycelium renders 

 ineffective treatment of seeds by ordinary surface disinfectants. 

 Certain workers have shown, however, that certain seed-borne 

 plant parasites lose their vitality more rapidly than the seeds 

 carrying them. Barre ('12) found that the cotton anthracnose 

 organism remains alive in the seed until the second season, but 

 that 3-year-old seed produces disease-free plants when planted 

 in the field. Rapp ('19), working with bacterial blight of beans, 

 has found that 3-year-old beans produce disease-free plants. 

 Thus it seems probable that, in the case of pod and stem blight 



