249 

 CHERRY LEAF-BLIGHT (Cylindrosporium padi Karsten). 



The leaf-blight of cherries caused by the same species of fungus as 

 that producing plum leaf-blight, is very widespread. Scarcely a wild 

 species of the genus Prunus is entirely exempt from the disease, and at 

 all stages from seedlings in the seed bed to old bearing trees, cultivated 

 cherries are subject to its attacks. The greatest variation exists, how- 

 ever, as regards the susceptibility of different varieties, some being 

 nearly exempt and others, as the English Morello, materially damaged 

 by it. Remarkable cases of immunity are sometimes observed. Of 

 seedlings used for budding, only the Mazzard seems in any serious de- 

 gree damaged by the disease. In unfavorable years the defoliation is 

 so serious as to render the first year's growth of stocks almost insig- 

 nificant. Mazzard seedlings of the second year are also badly attacked. 

 The greatest damage probably occurs where Mazzard stocks are budded 

 with susceptible varieties, in which case the cumulative effects of the 

 disease appear. It should be noted here, however, that the cherry 

 leaves attacked by the parasite remain attached to the stocks long 

 enough to take on the yellow autumn tints characteristic of foliage 

 from which the valuable ingredients of potash and phosphoric acid 

 have been removed.* It is probable, although no experiments have to 

 my knowledge been made to establish it, that the premature fall of the 

 leaves does not entail so great a loss to the cherry seedling as does 

 the fall of the pear foliage, which drops while still green. 



The experiments in the prevention of this disease, extending over a 

 period of two seasons, were made upon the two well-known kinds of 

 stocks, Mahaleb and Mazzard. In 1891 only the stocks not yet budded 

 were treated, while in 1892 the stocks budded in the fall of 1891 were 

 sprayed, suitable control being left. 



For record of budding see pp. 258, 2GO. Bordeaux mixture and am- 

 moniacal solution of standard strength were employed in 1891; ammo- 

 niacal solution of standard strength and Bordeaux of one-third strength 

 in 1892.1 



JtfAHALEB CHERRY STOCKS. 



1891. One row of 449 stocks was planted and treated with fungicides 

 at the dates described for all the stocks on p. 263. One-half, excepting 

 controls, received 6 and the other 3 sprayings. One-half were treated 

 with ammoniacal solution, the other with Bordeaux. As mentioned in 

 Bulletin No. 3,J where an account of this experiment has already been 



'According to the prevailing views of tlie physiological botanists, Pfeifer, Sachs, 

 Detiner, Wiesner, and others, the valuable mineral constituents of leaves aje with- 

 drawn from them at the same time as they become yellow and before they fall to the 

 ground; but the recent paper of Wehmer, Die dem Laulfall voraufyehende vermeint- 

 Uche flatten tleerung. <#-. d. denhch. lot. Gesellsch. 10 Jahrg., Heft. 3, pp. 152-163, 

 indicates that the grounds for this belief may not have been sufficiently proven, and 

 the whole subject needs further investigation. 



t See p. 262 for formulae of all fungicides used. 



tOp. cit.,-p, 58. 



