DISEASES 221 



a grayish-white spot about | inch in diameter. Several raised, 

 concentric grayish or brown rings may form at irregular intervals in 

 the muddy-brown diseased tissue beyond the frog-eye center. The 

 circular growth of the center spot is often modified in the extended 

 growth, becoming lopsided. None of the above characteristic mark- 

 ings, with the exception of the frog-eye nucleus, is clearly defined 

 on the undersurface. The coloring of the latter is a uniform dark- 

 brown, punctuated by the round and lighter-colored frog-eye spots. 



Leaf spot is caused by a fungus which lives over winter on fallen 

 leaves and in cankers on the limbs and trunks of trees. In the 

 spring are produced spores, which germinate when they fall on the 

 young apple leaves, if moisture is present, then penetrate and grow 

 in the leaf tissue, causing the spotted appearance described above. 



Treatment. The treatment prescribed for apple scab will be 

 found effective against leaf spot. To insure best results, apply the 

 first spraying of lime-sulphur just before the cluster buds open ; 

 do not wait until the full leaf crop unfolds. Fertilization and clean 

 cultivation render trees more resistant to the disease. Trees grow- 

 ing on well-limed soils have been observed by Mr. Chase to be less 

 seriously attacked than trees on soil deficient in lime. 



Diseases affecting the Blossoms 



Blight. The blossoms are affected by a fungus which is locally 

 called blossom blight. This is, so far as known, the same fungus 

 that is named pear blight, a description of which is given on page 

 210. The effect of this fungus on the blossoms is to blast them 

 so that their normal functions cannot take place. Careful cutting 

 away of diseased portions and conscientious spraying will tend to 

 wipe out this blight. 



Scab. Sometimes scab affects the blossoms of the apple and 

 destroys great numbers of them. Careful attention to spraying will 

 tend to subdue the scab fungus in time. 



Diseases affecting the Fruit ox the Tree 



Black rot (Spharopsis malorum). This disease, commonly known 

 as the New York apple canker, attacks the fruit as well as the bark. 

 It mav attack the fruit while growing on the tree, but is more 



