30 MISC. PUB. 52 6, U. S. DEPT. OF AGRICULTURE 



Pyrethrum is used principally against houseflies, mosquitoes, cock- 

 roaches, body lice, leaf tiers, plant bugs, leaf hoppers, mushroom flies, 

 the imported cabbage worm, and the cabbage looper. 



Pyrethrum is used both in dusts and sprays. One formula for a 

 dust for the control of the potato leafhopper on bean is made up as 

 follows : 



For small For large 



Pyrethrum powder quantities quantities 



(1.3 percent pyrethrins) 5 tablespoonfuls. 4 pounds. 



Sulfur 5 cups. 96 pounds. 



Manufactured dusts which generally contain from 0.1 to 0.3 percent 

 of pyrethrins may be purchased for use by the home gardener. The 

 dust containing 0.3 percent pyrethrins is recommended for general 

 purposes. 



When used as a spray, pyrethrum is generally applied as a diluted 

 extract. The pyrethrins and resins are extracted with a solvent 

 and mixed with emulsifying agents for use with water on plants, 

 or with light kerosene for use as fly sprays in buildings, or with oil 

 emulsions for a mosquito larvicide. Moderately concentrated pyreth- 

 rum extracts (containing 2 to 3 percent of pyrethrins) properly 

 prepared and packaged do not deteriorate rapidly. Such various 

 concoctions should be used in accordance with the manufacturer's 

 recommendations. 



Caution. — Although the danger from human consumption of 

 traces of pyrethrum is not great, persons allergic to ragweed in 

 some instances are subject to attacks of hay fever when exposed 

 to pyrethrum. 



ROTENONE-CONTAINING ROOTS 



Rotenone-containing insecticides are prepared from the roots of 

 certain tropical and semitropical plants which, in addition to rote- 

 none, usually contain other toxic ingredients, including toxicarol, 

 deguelin, tephrosin, sumatrol, and a few others. Rotenone, 

 C 2 3H 22 6 , is considered the most important. The plants from which 

 these toxic substances are derived include species of Derris (prin- 

 cipally elliptica) , which are grown extensively in Malaya and the East 

 Indies, and species of Lonchocarpus (nicou and uructi), of South 

 America. Experience indicates that usually there is little difference 

 between the various roots, provided they are of equal rotenone con- 

 tent. The rotenone content is usually 4 to 5 percent, and there is 

 present about 2^ to 3 times as much of other extractives. Rotenone, 

 in addition to being toxic to many insects, is also poisonous to fish but 

 is not harmful to warm-blooded animals when eaten in small amounts. 

 Therefore, the use of ground roots is permissible on leafy vegetables 

 which are consumed by man or domestic animals. 



The roots are usually ground sufficiently fine so that most of the 

 powder will pass through a 200-mesh screen. The powder is diluted 

 to give a very small amount of rotenone in the mixture to be applied. 

 It may be stirred into water and applied as a spray or mixed with 

 some fine dust for treating infested plants. For sprays the final 

 rotenone content may range from as low as 0.005 to 0.025 percent or 

 higher, and for dusts from 0.5 to 1.0 percent or higher. 



