270 SEVENTEENTH AND EIGHTEENTH 



fourth of an inch in diameter. This canker is not so com- 

 mon nor so serious as the preceding one. 



Leaf Spot (Phyllosticta pinna Sacc. & P. Limitata Pk.). 

 This fungus produces brown, circular, sharply defined spots 

 on the leaves. The disease has been a serious one in certain 

 localities the past year. In some cases nearly all of the 

 leaves had fallen by the middle of August, the tree being 

 thus deprived of its carbon food supply during a large 

 part of the summer. The disease has been worst in un- 

 cultivated orchards located on poorly drained soil. Spray- 

 ing has had little or no effect upon the disease. 



Baldwin Fruit Spot. This appears as small circular 

 slightly sunken spots on the fruit, greatly injuring its ap- 

 pearance. It is especially common on Baldwins but also 

 occurs on Porters and on other varieties. The cause of the 

 disease is not known, but the fact that it is greatly re- 

 duced by spraying indicates that it is of fungous origin. 



Fire-blight or Tw^ig-blight {Bacillus arnylovorus Bur- 

 rill). This disease attacks the leaves and twigs of apple 

 trees, causing the death of these parts. It has not been seen 

 on apple trees the past year except when located near pear 

 trees affected with the same disease. 



Pear Diseases. 



Pear Scab [Fusicladiuin pirinuni (Lib.) Fckl,]. The scab 

 on pears is very similar in appearance to that on apples. It 

 has been common the past year only on the Flemish Beauty. 



Fire-blight or Pear-blight (Bacillus ainylovorus Burrill). 

 This disease is of bacterial origin. The bacteria gain en- 

 trance to the twigs through wounds or through the flow- 

 ers. The first evidence of the disease is the scorched and 

 blackened appearance of the leaves. The shoots are also 

 affected, the disease spreading rapidly backward through 

 the branches, soon killing large limbs and sometimes the en^ 

 tire tree. Small drops of a mucilaginous fluid often ooze 

 out of ruptures in the bark. In this fluid one finds myriads 

 of bacteria. Insects feed upon this material and by their 

 subsequent visits carry the disease to other plants. 



