INSECTICIDES 55 



spider, on whatever plants it may occur, and for other mites which 

 infest citrus fruits. It may be dusted on the infested plants or trees 

 or applied with any other insecticide, using 1 or 2 pounds to 50 

 gallons. For citrus-mites the .lye-sulfur wash and sulfide of lime 

 are extensively used. Sulfur is frequently dusted in poultry 

 houses to rid them of lice, and may be mixed with lard and rubbed 

 on the skin of domestic animals affected with lice. 



11. Pyrethrum, buhach, or Persian insect powder, is made by 

 pulverizing the petals of the pyrethrum blossom, and kills insects 

 by clogging their breathing pores. It is not poisonous to man or 

 domestic animals and may therefore be used where other insecti- 

 cides would be objectionable. It is chiefly used for household 

 pests, and in greenhouses and small gardens. It deteriorates 

 rapidly with age and should be kept in tight cans. An objection 

 to much commonly bought is that it has been kept in stock too 

 long by the retailer, thus losing its strength. Large users buy 

 direct from the only American manufacturers, the Buhach Pro- 

 ducing Co., Stockton, Cal. It may be used as a dry powder, 

 pure or diluted with flour, or in water at the rate of 1 ounce to 2 

 gallons,, which should stand a day before using. For immediate 

 use it should be boiled in water for five or ten minutes. It is fre- 

 quently burnt in rooms to destroy mosquitoes and flies, for which 

 it is effective, without leaving any odor after the room is 

 aired.* 



12. Tobacco. A tobacco decoction may be made by boiling or 

 steeping tobacco leaves, stems, and refuse in water at the rate of 

 1 pound to 1 or 2 gallons. This may be diluted slightly according 

 to the strength of the tobacco and the insect to be combated. 

 Such a decoction is an excellent remedy for dipping plants affected 

 with aphides, and may be used as a spray for plant-lice and similar 

 soft-bodied insects. Various extracts and solutions of tobacco are 

 now sold by manufacturers which are extensively used in spraying 

 "against plant-lice, and which are proving more satisfactory on 

 account of their uniform strength. Tobacco dust has been used 

 successfully against root-infesting aphides by removing the sur- 



* See Farmers' Bulletin, 444, U. S. Dept. Agr., p. 7. 



