Arsenate of Lead. Arsenate of lead may be applied to plants 

 in the form of a spray with water as a vehicle, or in a powdered 

 form may be dusted on. Both forms can be bought on the market 

 ready-made, or they can be made at home. They are generally 

 useful for defoliating insects and the young stages of stem borers 

 and leaf rollers. Prepared arsenate of lead is applied at the rate 

 of 3-15 lbs. to 100 gallons of water. To prepare arsenate of lead 

 from its components, use 3 parts of pulverized arsenate of soda 

 to 7 parts of pulverized acetate of lead. These dissolved in warm 

 water and united form a white precipitate which should be kept 

 covered with water until desired for use. The powdered arsenate 

 is probably more easily and cheaply applied to some plants and 

 is more effective for some insect pests, the boll worm for instance. 



Paris Green. Paris green sometimes forms a substitute for 

 asenate of lead and if a guaranteed brand and mixed with lime 

 is just as effective as lead arsenate and perhaps cheaper. The 

 caustic properties of par is green (due to the free arsenious acid 

 it contains) makes its use more or less unsafe and the lime is 

 added, usually in equal proportion to the par is green, to over- 

 come its tendency to burn. Paris green is applied at the rate of 

 1 lb. of paris green to 100-250 gallons of water. It is also some- 

 times dusted onto plants, but is then apt to burn. 



White Arsenic. White arsenic is used only in insect baits. 

 The bait is prepared by mixing arsenic and bran, middlings or 

 flour, with the addition of thin molasses. The proportions are 

 1 lb. of arsenic to 20-50 lbs. of bran. Spread in the field, around 

 the plants if desired but not so near to them that the arsenic dis- 

 solved by the rain will burn them. The arsenic is also sometimes 

 mixed with freshly cut alfalfa or sorghmn and distributed over 

 the fields to bait insects. Baits are very useful in Hawaii in 

 coping with cutworms, army worms, and wireworms. 



PETROLEUM INSECTICIDES. 



Petroleum insecticides act by external contact, causing irrita- 

 tion and interfering with the vital functions of the insect. Their 

 use is confiuod largely to insects with sucking uionthparls, wliicli 



