Nature-Study Agriculture 



Sprays for 

 biting 

 insects ; 

 internal 

 poisons 



Lead 

 arsenate 



The 



importance 

 of spraying 

 at the right 

 time 



U. S. D. A. 



FIG. 151. 



Apples ready to spray for codling worm (left) ; too late 

 to spray (right). 



has long been used for this, but because it is hard on 

 tender plants another arsenical compound called " lead 

 arsenate " is now more commonly used. Lead arsenate 

 sticks to the leaf better than Paris green does, and as it 

 is white one can tell more easily when the plants are 

 well covered with it. Lead arsenate is sold either as a 

 paste or a dry powder. Either form can be used in a 

 water spray, or the powder may be dusted on the plants. 

 The dry powder sticks better if it is used when the dew is 

 on the leaves. 



The time when an insect can be reached and affected 

 most easily is the best time for spraying. The case of 

 the codling moth of the apple illustrates this. The 

 moth lays its eggs a few weeks after the trees have begun 

 to bloom. The eggs hatch into tiny larvae, and these 

 usually crawl to the blossom ends and begin gnawing 



