A Study of Meadow-Crop Diseases in New York 79 



that " some of these Fusaria are weak parasites which are able to infect 

 clover but require the cooperation of other deleterious agencies to induce 

 fatal results." 



DOWNY MILDEW 



Peronospora trifoliorum, the cause of downy mildew, was found once 

 on red clover in the State, but it occurs more extensively on alfalfa (Stewart 

 and others, 1908:394). Patel (1926) found the disease limited to alfalfa 

 and yellow trefoil. 



DODDER 



Dodder occurs, but it is relatively uncommon on clover and alfalfa. 

 Stewart and others (1908:361-379) give notes on this disease in the State. 



RHIZOCTONOSIS 



According to Stewart (1919: 175), Rhizoctonia causes the leaves of white 

 clover under moist conditions to rot. Rhizoctonia crocorum (Pers.) DC. 

 may occur on clovers and alfalfa in the State, since it is known to occur 

 here on potatoes (Plant Disease Reporter, Supplement 34: 149. 1924) but 

 it has not been seen by the author. Recently Buddin and Wakefield in 

 England (1927) have connected the fungus with Helicobasidium purpureum 

 (Tul.) on fairly good evidence. Stevens and Wilson (1912) report a Rhi- 

 zoctonia as causing a root rot of clover in North Carolina. 



SCLEROT1NIA STEM CANKER 



Sclerotinia stem canker was collected once in New York at Phelps in 

 1901 by Stewart (1908:387). Gilbert and Bennett (1917), who have pub- 

 lished a good American account of this disease, believe that Stewart's 

 fungus is S. trifoliorum. The writer made a thorough search for this 

 disease during June, 1928, but discovered no trace of it in this State. 



THIELAVIA ROOT ROT 



Thielavia basicola has been found to cause root rot on red clover in New 

 York (Burkholder, 1916: 104). It sometimes affects clover in Connecticut 

 also, according to Gilbert (1909:20). It was not found by the author 

 during the seasons he has been in the field. 



BLACK STEM 



Black stem recently reported by Valleau and Fergus (1929) occurs 

 destructively on red clover in New York. It may be mistaken easily for 

 anthracnose, but no fruiting structures of a pathogene have ever been seen. 

 The cause of the disease is unknown. 



