EXPERIMENT 8TAT1()X UKTOKT. 541 



rogard to the rust, has been one of groat profit, and the same kind 

 of watchfulness may be exercised with' all kinds of crops.. 



In closing it is remarked that the fungus in question of the lima 

 beans is a mildew closely related with several others, as the ones 

 upon lettuce, grape, onion, spinach, etc. It is well, therefore, to 

 reserve the terms "blight," "rot,*' and even "mold," for othfer forms 

 of fungi. Whenever any of the three last names arc mentioned in 

 connection with the lima beans, the trouble is more than likely the 

 work of one and the same mildew. 



The Rotting of Potatoes. 



The rotting of potatoes was reported in the Weather and Crop 

 Bulletins as early as August 4th, and for weeks the number of reports 

 of potato rot increased. On August 18th the correspondents reported 

 as follows: "Potatoes are rotting badly;" "Potatoes rotting in many 

 fields;" "Potato rot increasing m some places." For August 2.5th 

 and September 1st the common expression was "Potatoes are rotting 

 badly." 



The common field potato is troubled with a number of plant 

 diseases, all of which may have had some part in the wholesale decay 

 above indicated. An examination of the fields, however, leads to the 

 opinion that the chief trouble has been the so-called potato rot. In 

 1889 there was a similar outbreak of this disease, and a leaflet ( Special 

 Bulletin G) was prepared and circulated among the potato growers. 

 From it some of the facts connected with the potato rot are gathered. 



This disease is caused by a fungus (Phytophthora infestans D By.) 

 which is closely related to the downy mildew upon the grape. It 

 first attacks the potato leaves, causing them to cui-l and become 

 "frosty" upon the under side, after which they quickly turn brown 

 and decay. From the leaves the fine threads of the fungus pass to 

 the stems, and, if the conditions are favorable, the vines are soon 

 dead and leafless. The potatoes are the last to be attacked, and, 

 owing to their size and solidity, may be considerably infested inter- 

 nally with the fine filaments of the fungus before the condition 

 familiarly known as the rot becomes evident. From this it follows 

 that the loss from the decay of the tubers after harvesting the crop 

 may possibly Ije more than that occurring in the field. 



Conditions Favoring the Rot. — The first essential is abundant 

 moisture. Since 1840, when it is thoudit that the trouble was intro- 



