EXPERIMENT STATION BULLETINS. 



349 



DISEASES OF THE APPLE. 



APPLE SCAB. 



(Venturia Pomi (Fr.) Wint.) 



Fig. 1. — Apple leaves affected with the Apple scab fungus. (Original.) 



This disease of the apple commonly known as "scab" or in some cases "black 

 spot," is probably familiar to every grower of this fruit. It first appears in 

 spring on the young foliage producing velvety, olive colored patches. This 

 form is sometimes known as "mildew" or "leaf blig-ht." In severe cases the leaves 

 become shriveled and discolored, eventually falling off. The fungus also attacks 

 the stems of the young apples at blossoming time, especially if the weather at 

 this time is unusually cool and moist. This causes the young fruit to shrivel 

 and drop off, often greatly reducing the crop of mature fruit. 



The most characteristic effects of this fungus parasite, however, are found 

 on the fruit itself. Here the spots at first appear much like those on the leaves 

 but as the fruit develops the fungus works under the cuticle or outer layer of 

 the skin causing it to scale off. These spots on mature apples have a dark brown 

 or blackish color with a narrow border of a light gray color. The spots are 

 usually most numerous around the blossom end of the fruit. On badly affected 

 fruit the spots run together sometimes covering one-third of the surface. Deep 

 cracks often occur in such cases which allow the apple to dry out. 



Apple scab is without doubt the worst disease affecting this fruit. This is due 

 not alone to its destruction of the foliage and young apples nor to the unsightly 



