FORAGE CROPS 387 



The affected plants wilt and rot to the ground, and white 

 mats of mycelial threads, and later black sclerotia, are 

 found upon or within the dead stems. Sclerotia are es- 

 pecially abundant at the bases of the sick stems. Disk- 

 hke bodies, similar to those described in connection with 

 lettuce sclerotiniose, 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 has not yet attained 

 ^vide distribution in America, though it has appeared in a 

 serious way 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 affected fields to susceptible crops. 



Rust {Urmnyces Trifolii (Hedw. f.) Lev.). — The clover 

 rust is most injurious to the second crop, to which it may 

 cause a damage of 20 per cent or even 50 per cent if con- 

 ditions favorable to the disease — damp, cool weather — 

 obtain. 



This rust, long known in Europe, whence it is probably 

 adventive, was first reported in America in 1884. At the 

 present time it is found upon red, white, crimson, and 

 alsike clovers over a large part of the United States. 



It is one of the true rusts, and on the white clover pos- 

 sesses all of the three stages, cluster cup, summer or uredo, 

 and winter or teleuto spores. It attacks all green parts of 

 the plant. The most conspicuous and destructive stage 

 is the uredo, which is marked by an abundance of circular 

 or elongated chestnut-l^rown powdery sori. These may be 

 few and scattered, but more often they are quite abundant, 

 nearly covering the leaf. If abundant, the leaf turns black. 



