A Study of Meadow-Crop Diseases in New York 43 



been reported from all the States of the Union except Wyohiing, Nevada' 

 New Mexico, Arizona, and California, and from some of the provinces of 

 Canada. In 192o Kirby and Archer (1927:198) report it as becoming 

 of less importance, and Haskell (1928:347) says it was of still less impor- 

 tance in 1927. Reports for the country as a whole have not yet been 

 summarized for 1928, but, if New York may be taken as a criterion, the 

 disease is about as prevalent as in 1927. 



Salmon (1900:181-182) lists the distribution in full but he does not 

 differentiate between the various suscepts, so that it is impossible from 

 his records to determine how widely clover is affected in the various 

 countries of the world. 



Economic importance 



Although opinions differ, probably the majority of the plant-disease- 

 survey collaborators tend to hold with Valleau (Plant Disease Bulletin 

 6:11. 1922) that " it is questionable whether or not it is causing serious 

 damage." Edgerton (page 12 of the same bulletin) says that " the mil- 

 dew reduces the tonnage of the clover crop and will cause the hay to be 

 slightly off color and of poorer quality." Anderson (page 13 of the same 

 bulletin) reports that in parts of Illinois " the disease is so bad .... 

 that when the mower goes through a field a white cloud arises on all sides." 



Possibly those who believe that no damage is incurred have not 

 observed plants in the later stages of the disease. A large number of 

 leaves are killed and many others are severely injured. During a hot 

 day in late August or early September diseased plants partially wilt because, 

 no doubt, of the rapidly transpiring mildew mycelium which draws the 

 water from the leaves. A considerable amount of damage certainly results 

 from the mildew in an average year. 



Anderson (Plant Disease Bulletin 6:13. 1922) in Illinois states that 

 " those who handle the dried hay complain that the dust results in a 

 stinging sensation in the nose and throat," and Tehon (page 13 of the 

 same bulletin) in the same State says, " We have heard that a disease 

 or trouble similar to heaves has occurred in the southern part of Illinois 

 from feeding of mildewed clover to stock." Farmers have inquired 

 whether the diseased hay is injurious to stock. According to Haskell 

 and Wood (1923:251), "No actual cases of stock poisoning from this 

 cause were found and feeding experiments conducted with horses, cattle, 

 sheep and swine at the Tennessee Experiment Station resulted in no harm- 

 ful effects." Probably, however, horses subject to heaves should not be 

 fed mildewed clover hay unless it is sprinkled to lay the dust. 



As with other forage-crop diseases, estimates of loss are guesses at best. 

 Temple and Jehle (Stakman, 1922:243-244) estimated that in Maryland 

 in 1921 the second crop was reduced by 5 per cent and the entire crop 

 by 2 per cent. In isolated fields in New York the loss to the second 



