CONTACT INSECTICIDES 19 



2. Tobacco. 



3. Soaps. 



4. Oils. 



5. Lime-sulphur. 



6. Carbolic-acid emulsion. 



Pyrethrum 



Commonly called Persian Insect Powder/^ Dal- 

 matian powder, and Buhach; formerly imported 

 under two first names; now manufactured in 

 California under name Buhach. It is a powder 

 made from the pulverized flower heads of Chrysan- 

 themum cinerarice folium; contains a volatile oil and 

 kills by contact; harmless to human beings and to 

 plants. It is expensive and soon loses its effec- 

 tiveness w^hen exposed to the air. Buhach is 

 most apt to be fresh. It is used chiefly in green- 

 houses and in the household where it is usually 

 sifted dry on the plants or in the rooms. It may be 

 applied wet by steeping i ounce in a quart of boiling 

 w^ater for 5 or 10 minutes to which 3 quarts of cold 

 water should be added. 



Tobacco 



The insecticidal power of tobacco is due to the 

 nicotine it contains. Is often used as a dust ^^ 

 against plant and animal lice and against ticks. It 

 is said to be useful in controlling the woolly aphis 

 on the roots of apple trees and also acts as a good 

 fertilizer. It is a waste product of tobacco fac- 

 tories and costs about i cent per pound. 



Tobacco stems or leaves may be cooked or 

 steeped in water to remove the nicotine and form a 



38 xMarlatt— U. S. Dept. Agr., Ear's' Bull. 127, p. 16. 



Coquillet— U. S. Bu. Ent., Bull. 12, o. s. 

 3fl Smith— N. J. Expt. Stat., Bull. 213, p. 28. 



