DAIRY AND SEED IMPROVEMENT MEETINGS. 355 



characteristics of the disease is that the tops may, as a rule, 

 look fairly strong and healthy and give promise of a good yield, 

 but when dry weather comes, will ripen prematurely and the 

 yield will be disappointing, such potatoes as are produced being 

 numerous and below marketable size. 



The next picture shows the fruiting stage of the fungus 

 which grows up around the base of the stem of the potatoes, 

 producing a grayish felt-like growth. This latter may occur 

 without any apparent injury to the stem. 



The fungus not only attacks the main stem but the tuber- 

 bearing stolons, often cutting these off as soon as formed, or 

 before the tubers on them have attained any considerable size. 

 The next picture shows the base of the stem badly affected in 

 this way with the tubers clustered about and at the surface of 

 the ground. The next slide illustrates the potatoes dug from a 

 single hill. This is sometimes spoken of as "little potato dis- 

 ease." Here, as fast as the tubers are formed or had attained 

 but little size, they were cut off from the main stem by the 

 fungus. There are 39 potatoes in the hill. 



Frequently the fungus follows back along the stolons and 

 attacks the stem end of the tuber, as shown by the next picture, 

 where the base of the tuber becomes browned around the stem, 

 and sometimes a form of necrosis sets in and eats away the 

 tissues in this region. 



Occasionally tubers themselves may be attacked when young, 

 but not cut off from the stem. In bad cases of injury of this 

 kind they are apt to become badly cracked and misshapen, as 

 shown in the next picture. 



Sometimes, when the disease is very destructive, a peculiar 

 form of pitting of the surface, which apparently is caused by the 

 fungus, is observed. This resembles somewhat the channels made 

 by wireworms and we believe is frequently confused with their 

 work. The next picture shows tubers affected in this way, and 

 the next a cross section of the same. 



As yet there is very little that we can say regarding pre- 

 ventive measures. Corrosive sublimate seems to be the most 

 effective disinfecting agent for Rhizoctonia, but the seed planted 

 should be as free from the fungus as possible. The land on 

 which it occurs in a destructive manner should be given over to 

 other crops as long as possible before being again planted to 

 potatoes. 



