INSECT PESTS 221 



dance of plant food and good care and cultivation must 

 therefore be the first point to be attended to, but cannot 

 be wholly depended upon, for, when the season is right 

 for the rapid increase of insects or fungi, trees under 

 all conditions will be sure to be more or less injured 

 unless the work of spraying is promptly and thoroughly 

 done. Insecticides should be applied when the first 

 insects appear, and fungicides before the spores come in 

 contact with the host plant. If the first insect is de- 

 stroyed there will be no further trouble, and if the first 

 spore or seed of the fungus is destroyed, or, coming 

 into contact with the copper sulphate, fails to germinate, 

 there can be no further growth of that pest. Therefore 

 we should adopt the rule that "prevention is better than 

 cure," and it is certainly cheaper. 



INSECTICIDES (insect KILLERS ) 



The substances used to destroy insects on our plants 

 may be divided into two groups: Those that kill by 

 contact, and those that kill by being taken into the 

 stomachs of the insects, i. e., those killing "sucking" 

 insects and those killing "chewing" insects. 



1. Of the first, the most in use are Paris green, 

 London purple, arsenate of lead, hellebone, arsenate of 

 lime, arsenate of soda, white arsenic, etc. 



2. Of the second group most in use, we may men- 

 tion whale-oil soap, linseed oil, kerosene, crude petrol- 

 eum and pyrethrum or Persian insect powder. 



Promptness and thoroughness in the application 

 of insecticides should be the watchword. The best 

 pumps for the work in hand should be used, the prepara- 

 tion of the insecticides and fungicides should be most 

 carefully done, and in mixing and applying the greatest 

 economy of labor be practiced. In fact, in all the work 

 attending the growing and caring for any crop of fruit, 

 thorough mark and business dispatch must be the rule 



