250 THE SPRA YING OF FRUITS. 



MATERIALS AND FORMULAS. 



Paris-green. This compound of arsenic (aceto-arsenite of 

 copper) is the standard insecticide for all chewing and biting 

 insects, such as larvae (" worms") and most beetles. A pound 

 of it is used in two hundred to three hundred gallons of water 

 for fruit-plants. For apple and pear and plum trees, the 

 denser strength is generally preferred, but for peach-trees 

 (upon which it is seldom necessary to use it) the weaker 

 strength is recommended. If this mixture is to be used upon 

 fruit-trees, one pound of quicklime should be added, for re- 

 peated applications will injure most foliage, unless the lime 

 is used. Paris-green and Bordeaux-mixture can be applied 

 together with perfect satisfaction. Use at the rate of four 

 ounces of the arsenite to fifty gallons of the Bordeaux mix- 

 ture. The action of neither is weakened, and the Paris green 

 loses all caustic properties. Paris-green itself has slight fun- 

 gicidal properties. 



It sometimes happens that material which is obtained as 

 Paris-green contains no arsenic. If the material is genuine Pa- 

 ris-green, it will quickly and completely dissolve in common 

 strong ammonia, giving a beautiful, rich, dark blue, clear 

 liquid, while any of the compounds which would ordinarily be 

 substituted for Paris-green on account of their color and tex- 

 ture, will not behave in this manner in ammonia. Any insol- 

 uble residue is impurity. Chrome-green, which may be pro- 

 cured for Paris-green, will not dissolve in ammonia. 



London-purple. This is used for the same purposes as 

 Paris-green, and in the same proportions. It is an arsenite of 

 lime. Its advantages over Paris-green are its cheapness and 

 the greater ease with which it is held in suspension in water, 

 but these are not important merits. As it is very caustic, it 

 should be applied with two or three times its weight of lime, 

 or with the Bordeaux-mixture. The composition of London- 

 purple is variable, and unless good reasons exist for suppos- 

 ing that it contains as much arsenic as Paris green, it is better 

 to use the latter poison. Do not use London-purple on peach 

 or plum trees unless considerable lime is added. 



Substitutes for Paris-green. Paris-green is still the standard 



