338 



The Spraying of Plants. 



fly, but is only about a sixteenth of an inch in length. This 

 winged form is extremely active and difficult to capture. 

 Affected trees become much weakened ; the foliage is light 

 green or yellowish, and if the tree is badly 

 infested both the fruit and the foliage drop 

 prematurely to the ground. 



Treatment. The best method of over- 

 coming this destructive insect is to spray 

 the trees with kerosene emulsion, contain- 

 ing from 4 to 5 per cent of kerosene, as 

 soon as the first leaves have unfolded in 

 spring. The application should be made 

 very thoroughly, and it should be repeated 

 once or twice at intervals of ten days or 

 two weeks, if there is reason to fear that 

 many insects have survived. Treatments 

 made during the summer are also of value, 

 but the spray must be copious, and it must be thrown with great 

 force to destroy the adults. All applications should also be 

 made soon after a rain, for then the honey-dew is mostly washed 

 away, and the immature insects, or nymphs, may be reached 



FIG. 74. Adult psylla. 



FIG. 75. Cherry slug upon pear leaf. 



more easily by the emulsion. Winter applications of kerosene 

 emulsion as applied for plum scales have been recommended. 



Slug. The shiny dark-colored slug, which is so frequently 

 seen upon pear foliage (Fig. 75), is identical with the one found 

 upon cherry foliage. A description of the insect will be found 

 under CHERRY, but it will be well here to emphasize the neces- 



