556 



Journal of Agricultural Research 



Vol. VI, No. is 



Table I gives the results of these inoculation experiments with Diplo- 

 dia spp. 



Table I. — Results of the inoculations of tubers of Colocasia esculenta, X~anthosoma 

 sagittifolium, C. indica, and Alocasia sp. with Diplodia tubericola, D. maclurae, 

 D. gossypina, and Diplodia sp. from Mangifera indica 



/« None of the checks became infected. 



POWDERY GRAYROT 



Since this form of storage-rot has never been reported before, the 

 writer proposes that it be known by the name "powdery grayrot." 

 This, like many other common names of plant diseases, is somewhat 

 misleading, since the rot in its early stages is soft and, if invaded by 

 bacteria, is slimy on the surface. In the later stages, however, it becomes 

 powdery and gray, this appearance serving to distinguish it from the 

 other storage-rots. 



DESCRIPTION OF POWDERY GRAYROT 



This rot has been isolated repeatedly from tubers and corms from 

 Brooksville, Fla., and from specimens imported from Japan in May, 

 1 91 5. Infection usually begins in the wounds made by breaking the 

 tubers and corms apart, showing that it is probably strictly a wound 

 parasite. When infected at such a point, the rot may spread rather 

 widely over the surface, penetrating only half an inch or so; or it may 

 penetrate under a small area to the center of the tuber or corm, though 

 the number of specimens having been seen completely decayed by this 

 organism is relatively small. In the final stages this rot becomes rather 

 hard, dry, and powdery and is of a grayish color and crumbles when cut 

 with a knife. 



Numerous inoculation experiments have made it possible to study the 

 progress of this rot more in detail in the laboratory. The first evidence 

 of decay appears in 24 hours after inoculation on a cut surface, manifested 

 by the formation of an ocherous to salmon-orange color. This color 



