POWDERY DRY-ROT OF THE POTATO. 1 



By W. A. Orton, Pathologist in Charge of Cotton and Truck Disease and Sugar-Plant 



Investigations. 



INTRODUCTION. 



In recent years a new potato disease, which has been named the 

 "powdery dry-rot/' has come to the front. It has caused heavy 

 losses in several Western States from Minnesota to Washington and 

 is a special menace to those irrigated districts where the potato is 

 one of the main money crops and where the product must be shipped 

 many hundreds of miles to reach a market. Several instances have 

 recently occurred where carloads of potatoes were shipped from the 

 Northwest to Texas points and to Chicago. Leaving their point 

 of origin in apparent good order they arrived at their destination 

 badly decayed, were rejected by the purchasers, and had to be con- 

 signed to the dump. The cause of this rapid deterioration was the 

 powdery dry-rot. Such experiences are exceedingly harmful to the 

 reputation of a new potato district. Buyers will not erect ware- 

 houses or provide shipping facilities for a permanent trade, nor will 

 they purchase for distant shipment save at the producers' risk. It 

 is therefore imperative that the growers take every possible means to 

 prevent the spread of this disease. 



DESCRIPTION OF POWDERY DRY-ROT. 



This disease is an external dry-rot. It may start at any point on 

 the outside of the tuber or gain entrance at the stem end. It starts 

 most readily in wounded potatoes, but may spread to uninjured ones. 

 The spots are wrinkled, discolored, and somewhat sunken, externally 

 darker brown than the normal epidermis, internally sepia brown, with 

 a dark, discolored layer next the sound flesh. In the later stages 

 the decayed portions become dry and powdery, with internal cavities 

 filled with fungous mycelium. 



The cause of powdery dry-rot is a newly described fungus, Fusa- 

 rium tricJiothecioides Wollenw. 2 



1 Issued Jan. 18, 1913. 



J Jamieson, C. O., and Wollenweber, H. W. An external dry-rot of potato tubers caused by Fusarium 

 trichothecioides Wollenw. Journal, Washington Academy of Sciences, v. 2, no. 6, p. 14(>-152, Mar. 19, 1912. 



[Clr. no] 13 



