Methods of Control 371 



pearance of the pest every year, although this date 

 depends somewhat on the climate of each season. 

 In destroying the green aphids, the contact poison 

 should be distributed as evenly as possible on the 

 insect itself. It is, therefore, best to spray for aphids 

 when they are actually found working on the plants. 

 To check chewing insects and fungous pests, however, 

 the applications are made before the parasites appear. 

 Before spraying it is necessary to have well in mind 

 which organism is to be destroyed, and the proper 

 ingredients to be used. To keep fungous pests in 

 check it is necessary to have the plant covered with 

 the fungicide all the time infection is feared or sus- 

 pected. This spraying is preventive, protecting the 

 plant from becoming infected. When the parasite 

 has penetrated the host, spraying is of little value in 

 saving the infected plant, although it will protect 

 others which are as yet healthy. It is essential that 

 the trucker be always ready to spray. Sometimes 

 retardation for even a day may prevent the attain- 

 ment of positive results. The timely destruction of 

 one insect, or of one spore, means the destruction of 

 countless generations of these pests. 



Thoroughness is as important in spraying as it is in 

 everything else in life. Especially is this true for the 

 control of fungous diseases. 



Spraying Machines 



Success in spraying often depends on the sprayer, 

 and especially on the nozzle. In small scale garden- 



