INSECTICIDES. 85 



oil emulsion. Any one requiring a made-up contact poison will find this 

 suitable ; other made-up contact poisons can be purchased ; McDougal's 

 insecticide is an example, which acts solely as a contact poison. It is 

 valuable as a ready-made and effective contact poison, which acts with 

 much the same effect at the same strength as crude oil emulsion, the 

 latter being far cheaper. Both have been thoroughly tested and both can 

 be recommended. 



Insecticides are not like patent medicines, requiring only to be applied 

 (or taken), when they do the rest. They must be used in good time ; 

 an acre of mustard that was badly infested with aphis required two hun- 

 dred and fifty gallons of insecticide to kill every aphis, or three times the 

 amount required to destroy the same aphis at the beginning of the attack 

 on another acre. They must also be applied intelligently and vigorously, 

 with the express object of destroying the insect and not because it is the 

 right thing to do. They must be applied properly, with an under- 

 standing of what they are meant for and will effect. 



