336 The. Spraying of Plants. 



it has pupated it is also well protected. If the pears are not 

 allowed to set, the larvae will be unable to develop, and the 

 recommendation has therefore been made that the trees be 

 sprayed while in blossom and all the fruit prevented from 

 setting. This might be accomplished by using an arsenical 

 spray, as white arsenic, but no experiments appear to have 

 been made to settle the point. Picking the affected fruit before 

 the larvae enter the ground has also been suggested, as well as 

 thorough cultivation to destroy the pupae. Thorough applica- 

 tion of kerosene upon the surface of the soil would also destroy 

 many of the larvae before they pupate. Professor Smith has 



FIG. 71. Pear leaf blister. 



said that heavy fertilizing applications of kainite, if made 

 early in July, will materially reduce the numbers of this insect. 

 Pear Leaf Blister (Phytoptus Pyri, Scheuten). Description. 

 The animal causing the reddish blisters so commonly seen 

 upon pear leaves early in the season (Fig. 71) is a true mite 

 (Fig. 72). It passes the winter under the outer scales of the 

 buds, and as soon as warm weather starts the trees into growth 

 it abandons its winter quarters and begins to feed upon the 

 juices of the young foliage. The insect enters the leaves, where 

 it is entirely protected from all applications of insecticides. 

 The presence of this pest causes the formation of small swell- 

 ings which are dull red early in the season, but later they turn 



