Forage Crops 



329 



sori of the rusts as to lead the casual observer to mistake the 

 disease for a rust. Though the disease is often of considerable 

 damage, no treatment is known. 



Wilt ^^'^ {Sclerotinia trifoUorum. Eriks.). — The fungus caus- 

 ing this wilt is probably identical with that of the wilt of 

 alfalfa. It was first noted in America, in Delaware, by 

 Chester in 1889, later in New Jersey by Halsted. 



The affected plants wilt and rot to the ground. White 

 mats of mycelial threads, and later black sclerotia, are 

 found upon or within 

 the dead stems. Scle- 

 rotia are especially 

 abundant at the bases 

 of diseased stems. 

 Disk-like bodies, simi- 

 lar to those described 

 in connection with 

 lettuce drop, develop 

 from the sclerotium 

 and bear spores which 

 spread the infection. 

 While this malady has 



been very destructive in Europe upon several varieties of 

 clover, it is not yet of wide distribution in America, though 

 it has appeared as a serious pest in a few fields. 



It is exceedingly difficult to eradicate when it has once 

 gained foothold, and the European recommendation is to 

 avoid planting the infested fields to susceptible crops. 



Rust {Uromyces sps.). — The clover rusts are most in- 

 jurious to the second cutting, to which they may cause a 

 damage of 20 or even 50 per cent if conditions favorable to the 

 disease — damp, cool weather — obtain. These rusts, long 

 known in Europe, were first reported in America in 1884. At 

 the present time they are found upon red, white, crimson, and 

 alsike clovers over a large part of the United States, though 

 of different species, or at least different biologic races upon 

 some of the different hosts. 



Fig. 172. — ■ Clover leaf showing spots of 

 black-mold. Original. 



