[Vol. 10 



166 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



of soybean, seed-borne infection may be eliminated naturally 

 with increase in age of the diseased seed. 



Inasmuch as this fungus is able to maintain its viability during 

 the winter and produce pycnospores on old stems lying in the 

 field in the spring, a very evident and important precaution in 

 control is removal of diseased plant parts after harvest. Doubt- 

 less, this can be accomplished most economically by plowing them 

 under deeply. Rotation is suggested as a further measure of 

 precaution. 



Summary 



(1) A disease herein called pod and stem blight of soybean 

 has been studied and described. 



(2) The disease is not known to be widely distributed, having 

 been found to date in only 3 localities, all of which are in North 

 Carolina. 



(3) The disease occurs on pods, stems, and infrequently on 

 leaves. It causes a premature death of plants, a failure of 

 young ovules to develop, and a moulding and decay of seeds in 

 later stages of development. 



(4) The presence of the causal organism is manifested by the 

 appearance of pycnidia more or less generally distributed over 

 the stems and pods. Perithelia have never been found in the 

 field, but have developed in cultures of 2 strains isolated from 

 diseased pods. By pure culture methods the genetical relation 

 of the perithecial and pycnidial stages of the causal organism 

 has been demonstrated. 



(5) The causal organism is believed to have been hitherto 



undescribed. Its characters place it in the genus Diaporthe 



Nitschke, and in reference to its host it has been assigned the 

 name Diaporthe Sojae. 



(6) The causal organism has been isolated from stems, pods, 

 and seeds. It has been observed to cause the death of very 

 young seedlings by growing from the seed-coat to the hypocotyl 

 and causing it to decay. Successful inoculations have been made 

 in the field and greenhouse and the organism has been recovered 

 from plants diseased as the result of artificial inoculation. 



