[Vol. 10 



112 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



the losses caused by, pod and stem blight of soybeans are closely 

 correlated with rainfall of the summer season. During the 

 rainy season of July and August of 1920 the disease spread 

 rapidly from diseased to adjacent healthy plants, causing con- 

 siderable damage. With the inception of dry weather a marked 

 falling off of new infections was observed. In the summer of 

 1921, a season notable for a deficiency in rainfall, very few dis- 

 eased plants were found, and on these the disease usually involved 

 the stem only near the ground level. Moreover, infection did 

 not spread noticeably to neighboring plants. 



The summers of 1920 and 1922 were similar with respect to 

 amount of rainfall. However, during the latter season, the 

 relative humidity was not maintained so constantly at a high 

 point, the rainy period being interrupted by longer periods of 

 drying sunshine. In this season the disease was more abundant 

 than in 1921, but notably less severe than in 1920. 



Occasion has permitted no experiments to determine t he amount 

 of loss due to this disease. However, it is evident from field 

 observation that, in case of varieties maturing during the wet 

 seasons, very considerable losses occur. This is due largely to 

 the moulding and decay of half-grown seed, and, conservatively 

 estimated, the loss amounted to 15 per cent of the crop from 

 Black Eyebrow in 1920. 



Description of Pod and Stem Blight 



This disease attacks pods, stems, and leaves. It is seldom 

 found on pods when not also present on some part of the stem 

 of the same plant. Conversely, it is often found on stems when 

 there is no macroscopic evidence of its presence on pods, par- 

 ticularly in dry seasons. The disease makes its appearance first 

 during the warm rainy weather of summer on individual plants 

 standing at intervals a: 



time 



? usually 12-18 inches high and the first pods formed are 

 about half grown. The diseased plants are smaller than the 

 average healthy ones and are usually overlooked by the casual 

 observer. When found, these plants are usually dead, and at 

 least the lower part of the stem bears numerous pyenidia. The 

 infective material spreads rapidly with continuance of rainy 



