30 MISC. PUB. 526, U. S. DEPT. OF AGRICULTURE 
Pyrethrum is used principally against houseflies, mosquitoes, cock- 
roaches, body lice, leaf tiers, plant bugs, leafhoppers, mushroom flies, 
the imported cabbageworm, the cabbage looper, and the corn earworm. 
Pyrethrum is used in both dusts and sprays. One formula for a 
dust for the contro: of the potato leafhopper on bean is made up as 
follows: 
For small For large 
Pyrethrum powder quantities quantities 
GES. percent pyrethrins) =>" =e 5) tablespoonfuls. 4 pounds. 
St Burtt ees ee aes ae ee eee 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 of 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. 
A highly refined white mineral oil of from 100 to 150 seconds Say- 
bolt viscosity at 100° F., containing 0.2 percent of pyrethrins, is used 
for injection into the silk masses of sweet-corn ears to prevent their 
becoming infested by the corn earworm. Oleoresin of pyrethrum 
should be used in preparing this insecticide, and not pyrethrum ex- 
tracts containing highly refined kerosene or other solvents likely to 
impart an undesirable odor or flavor to the corn. About a 20-drop dose 
of the prepared oil is injected into the basal portion of the silk mass 
of each ear after the silks have begun to wilt and all danger of inter- 
ference with fertilization is past. A force oil can or, in the case of 
small garden plantings, a medicine dropper is used for this purpose. 
Caution.—Althovgh 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.3H,.O¢, is considered the most important. The plants from which 
these toxic substances are derived include species of Derris (prin- 
cipally edliptica) , which are grown extensively in Malaya and the East 
Indies, and species of Lonchocarpus (nicou and urucu), 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 
2 Wartime conditions have led to certain restrictions on the use of rotenone insecticides, 
and these restrictions are subject to change dependent upon the supply. For up-to-date 
information on the subject consult the War Food Administration, Chemicals and Fertiliz- 
ers Branch, Chemicals Division, Washington 25, D 
~~ 
