220 THE APPLE 



fails satisfactorily to qualify as a control, and has manifested de- 

 cided defoliating tendencies, causing the leaves to assume a light 

 yellowish appearance and finally to drop. The action of atomic 

 sulphur is apparently toxic, so that the leaf is gradually discolored, 

 its functions are impaired and finally cease, and the leaf falls. 

 This defoliation stops after a time, but is renewed with each spray- 

 ing. However, Mr. Chase r says that he has not observed it com- 

 pletely to denude a tree, the defoliation never going beyond a very 

 appreciable thinning out. The whole process, as to coloring and 

 dropping, is similar to that which accompanies the natural shed- 

 ding of the leaves at the approach of winter. 



The first spraying with 2 gallons of prepared lime-sulphur to 

 50 gallons of water just before the cluster buds open should be 

 followed in two or three weeks by a second spraying with the same 

 material, in the proportion of i| to 50, and by a third of the 

 same strength three weeks later. This schedule reduced the scab 

 to an insignificant consideration. 



Apple-leaf spot (Sph&ropsis malorum, Peck). One of the most 

 destructive diseases of apple foliage is known as leaf spot or frog 

 eye. It is more or less prevalent every year, and in favorable sea- 

 sons the defoliation produced by it is very serious. Like most 

 fungous diseases, it flourishes best where there is an abundance of 

 moisture. On apple trees located on low, poorly drained land, 

 where there was little air drainage and the moisture on the leaves 

 and in the soil remained longest, Mr. Chase repeatedly found that 

 the young leaves were heavily smitten by the disease. With the 

 coming of dry weather the defoliation ceased and the trees leafed 

 out anew. The loss of foliage in these instances had a markedly 

 depressive effect on the growth of the fruit. 



' Leaf spot is another of the apple diseases appearing soon after 

 the leaves are out in spring. Its period of greatest activity is con- 

 fined to spring and early summer. The first indication of it on the 

 leaf is a small, grayish, circular spot. When the diameter of this 

 spot has reached about \ inch a well-defined, dark-brown raised 

 margin is developed. Numbers of spots appear on tfypt-Jeaf simul- 

 taneously. A single mature spot has a diameter varying'from ^ to 

 I inch, or more. At the center of each diseased area there is 



1 See p. 217. 



