Dec., 1909.] 



SOME APPLE DISEASES. 



Ill 



nity to attack it, hence sprayings made after a disease is tho- 

 roly started are usually inefficient and often without evident 

 results. 



Heavy dews and cloudy, damp weather are favorable to the de- 

 velopment of fungous diseases. The weather plays so important 

 a part in this connection that it is sometimes given the entire 

 credit for the disease. It must be borne in mind, however, that 

 the real cause of the disease is the fungus itself. 



]\Iuch can be done towards the prevention of diseases by the 

 proper selection of an orchard site and by careful and thoro 

 pruning. Orchards located on high land with good air drain- 

 age are much less susceptible to fungous diseases, and also to 

 winter injury, than those in the valleys. If a tree is pruned so 

 that sunlight and air have free access to all its parts the oppor- 

 tunity for infection by fungi is greatly reduced. 



APPLE SCAB. 



Venturia Pomi (Fr) Wint. 



The scab is one of the most serious diseases of the apple in N>w 

 Hampshire. Some varieties, such 

 as the Mcintosh, can scarcely 

 be made to produce salable fruit 

 without thoro treatment for its 

 prevention. The disease appears 

 first on the leaves. Here it may 

 be evident early in June as 

 slightly elevated spots of a lighter 

 green color. At this stage the 

 mycelium of the fungus is largely 

 beneath the cuticle. It soon 

 breaks thru to the surface, giv- 

 ing the leaf a velvety, oliva- 

 ceous appearance (Fig. 1). Spores 

 are produced in abundance and 

 probably serve as the chief source 

 of infection for the fruit. As a 

 result of the fungous attack the leaves often become distorted 

 and finally fall early in the season. The leaf surface is thus 



Fig. 1.— Apple scab as seen on the fo- 

 liage. 



