DISEASES OF PLANTS 



243 



bad. The leaves also show the shot-hole effect. On 

 the almond the greatest effect is seen 

 in the leaves, which develop shot- 

 holes and fall from the tree. 



Cherries, plums, and prunes are 

 not so commonly affected. 



Other kinds of shot-hole fungi 

 exist, but have not caused serious 

 trouble. (Utah Experiment Station, 

 Bulletins 55, 65.) 



BACTERIAL DISEASES 



Pear blight. This very well-known 



J FIG. 141. Pear blight 



disease begins by attacking young attacking flowers 



flower buds (figure 141), and spreads 



downward on the twigs, causing black streaks on the 



smaller branches. These streaks run down upon the 



larger branches to 

 the trunk and finally 

 kill the tree. The 

 disease attacks not 

 only pears, but also 

 apples, quinces, and 

 loquats. It is caused 

 by bacteria, and it is" 

 believed that these 

 are carried from tree 



FIG. 142. Pear blight entering trunk of 

 tree through a small infested branch 

 whose leaves are already dying. 



