286 



Bulletin 276. 



in winter for San Jose Scale. Just where and how the spores are carried 

 over is, as pointed out before, an unsettled question. It seems probable 

 that they are lodged on the twigs or bud scales. Farrand ('04) found 

 that Curl was prevented on trees sprayed with copper sulfate and 

 drenched with water an hour later to wash off the spray. From this 



and from the fact that spray- 

 ing at almost any time during 

 the dormant period seems ef- 

 fective, it would seem that the 

 spores are at once killed by 

 the fungicide. The early stu- 

 dents of this disease were skep- 

 tical concerning the possibility 

 of controlling it by spraying. 

 Tliis conclusion was drawn 

 from the opinion generally held 

 at that time that the disease 

 was carried over by perennial 

 mycelium in the twigs. For 

 this reason it was advised by 

 many to cut back diseased 

 shoots, and even the removal 

 of diseased leaves was pro- 

 posed by some. These meas- 

 ures were found to have very 

 little or no effect in controlling 

 the disease, and it has since 

 been learned that the conclu- 

 sion that the parasite wintered 

 in diseased twigs to any ex- 

 tent was erroneous, since the 

 percentage of Curl carried over 

 by mycelium in the twigs is 

 extremely small. A very complete account of this and of the develop- 

 ment of the present methods of treatment is given by Pierce ('00) . Accord- 

 ing to his statement the practice of spraying for Curl during the dor- 

 mant period dates to observations made in California on the effect of 

 lime-sulfur solution as used for San Jose scale. This preparation, so the 



Fig. S: 



-A branch from a tree sprayed early 

 with bordeaux mixture. 



'04. Farrand, T. A., Mich. Report of South Haven Sub-station fi>r 1903, 

 Special Hul. 27 : 17. 



'00. Pierce, X. B., U. S. D. A, Div. Veg. Phys. and Path., Bui. 20:46-65. 



