INSECTICIDES 51 



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.* 



11. 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 aphids, 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 aphids by removing the sur- 

 face soil and applying a liberal dressing of the dust and then 

 covering. The rains leaching through the tobacco carry the 

 tobacco water to the affected roots and destroy or repel the 

 aphids. 



12. Commercial Tobacco Products are much more widely used 

 than home-made forms for the reason that they are uniform in 

 their strength and therefore more dependable in their action. 

 Practically all the commercial tobacco extracts are produced by 

 one company, the Kentucky Tobacco Products Co., of Louisville, 

 Ky. The most widely used of their products is called "Black- 

 Leaf 40 " and is generally recommended as the most satisfactory 

 remedy for soft-bodied sucking insects which require treatment 

 during the growing season of the plant. " Nicofume," another 

 of their products, differs from the " Black-Leaf 40 " in that it con- 

 tains nicotine in volatile form and is therefore useful as a fumigant 

 as well as for spraying. Its greatest value is in the greenhouse. 

 It will be found satisfactory usually to use these materials a little 

 stronger than is recommended by the company, otherwise the 

 directions accompanying the material will apply. 



13. Soaps of many kinds are efficient insecticides. They are 

 used as a substitute for kerosene emulsion and tobacco extracts 

 to combat aphids and other insects, especially on house plants and 

 in greenhouses. Various soaps are especially prepared to be used 



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



