SPRAYING 315 



more likely to injure plant tissue, and is less adhesive than 

 arsenate of lead. 



When quick results are desired Paris green and arsenate of 

 lead are sometimes used in combination. The usual propor- 

 tions for this combination are two pounds of arsenate of lead 

 and one-half pound of Paris green to fifty gallons of water. 

 This has been effective in cases where cankerworms were 

 so numerous as to threaten entire defoliation of apple trees. 



FIG. 157. Boiling lime-sulphur spray 



A class of Georgia high-school pupils getting some first-hand usable information 

 about the preparation of spraying solutions 



The insects which have sucking mouth parts are killed by 

 applying materials which destroy the body tissue, or smother 

 the insect by closing its spiracles, or breathing tubes. Of this 

 group the San Jose scale is one of the most destructive pests, 

 and the most effective control of it is secured by coating 

 the plants with a combination of lime and sulphur, known as 

 lime-sulphur wash (Fig. 157). 



There are many species of aphids, or plant lice, which some- 

 times cause serious loss. The green melon louse and the brown 

 plum louse are common, and occasionally the apple aphid is so 



