B. P. I.— 550. 



WART DISEASE OE THE POTATO; 



A DANGEROUS EUROPEAN DISEASE LIABLE TO P,E INTRO- 

 DUCED INTO THE UNITED STATES. 



INTRODUCTION. 



A new disease of the potato which has been exciting;- alarm in Europe 

 is likeh^ to be introduced into this country at any time. This circular 

 is issued to call the attention of American (growers and importers of 

 potatoes to this danj>-er and to uroe their cooperation in an effort to 

 prevent it from securing a foothold here. It is important that any 

 cases discovered be promptly reported and all possible means taken to 

 prevent its occurrence. 



DESCRIPTION OF THE DISEASE. 



The disease, which has been known as "warty disease," "black 

 scab," "canker," and "cauliflower," is one which attacks the tuber 

 principally, and consequently is not observed until harvesting time. 

 In a bad attack of the disease big, dark, warty excrescences, sometimes 

 as large as the tuber itself, appear on its sides or ends. "The growth 

 consists here of a mass of coral-like or more or less scabby excres- 

 cences or nodules, similar in appearance to the well-known crown or 

 root gall of apples. The adherent earth can be easily washed off 

 when the character of the growth })ecomes more apparent. It is not 

 spongy and not detachable from the tuber. It is of a somewhat lighter 

 color at the base and dotted with minute rusty-brown spots over the 

 surface. * * * In an advanced stage the tubers are wholly cov- 

 ered by this growth, having lost every resem])lance to potatooti. They 

 are lumps of irregular outline, never spherical or oblong, but simply 

 a mass of ragged and edged excrescences. * * * a still more 

 advanced stage occurs when the fungus has utilized every particle of 

 food stored in the tuber and has reduced it to a brownish-black soft 

 mass giving off a very unpleasant putrefactive odor. This is the most 

 dangerous stage of the disease, and the tubers which have reached it 

 can not bo harvested whole. Tiiey break in pieces, and thus the brown- 

 ish, pulpy mass, consisting almost entirely of spores of the fungus 

 ICir. 52] 3 



