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to hit all roaches. Since pyrethrum loses its effectiveness rather 
rapidly it was necessary to repeat the applications frequently. Sev- 
eral chemicals, such as piperony! butoxide and 7-propyl isome, are 
added to pyrethrum to make it more effective and more stable, so that 
the spray residue will remain toxic for a longer time. Such pyreth- 
rum combinations can be purchased in both hquid and powder form. 
Small amounts of pyrethrum are sometimes added to other insecti- 
cides to provide rapid knock-down and quick kill at the time of 
application. 
Sodium Fluoride 
Sodium fluoride has been used as a roach insecticide for years. It 
is not quite so effective as some of the newer materials. It is used asa 
powder, either undiluted or with an inert dust added. A mixture 
should contain not less than 50 percent of sodium fluoride. 
APPLYING ROACH INSECTICIDES 
Before applying a roach insecticide read carefully the section of this 
leaflet, Roach Habits as Related to Control, page 4. 
The proper application of any insecticide is fully as important as 
the choice of the insecticide to use. 
For use in the home a liquid insecticide is often more suitable than a 
powder. It can be sprayed into cracks, and other hiding places. It 
can also be applied on exposed surfaces where the roaches will crawl 
over the residue when they come out of hiding. A liquid spray should 
be used on vertical surfaces and on the underside of objects, where a 
dust would not adhere or would leave an undesirable visible deposit. 
The liquid can be applied with an ordinary household plunger-type 
insect sprayer. If large areas are to be treated, compressed-air 
sprayers, power sprayers, or other special equipment can be used. 
The sprayer should deliver a fairly coarse mist, which will wet the 
surface being treated. If the mist is too fine, it will float away in the 
air. Apply just enough spray to moisten surfaces thoroughly, but 
not so much that the hquid begins to run or drip. 
Placing a band of roach powder on the floor around the edges of a 
room, leaving it a day or two, and then cleaning it up, may kill many 
of the roaches, but it is not an adequate treatment. Many roaches 
may be able to go from their hiding places to sources of food and water 
without crossing the band of powder, or they may be actually repelled 
by the powder. 
A powder insecticide can be effective against roaches if it is properly 
applied with a puff duster of the bulb, plunger, or bellows type. Blow 
the powder into hiding places or onto surfaces where roaches run. A 
hight, uniform film is sufficient. Repeat when excessive moisture 
causes the powder to cake and become useless. 
When roaches are abundant, difficult to control, or firmly established 
in a building of loose construction, use both a powder and a residual 
spray for quicker and more satisfactory results. Apply the spray on 
vertical surfaces, in exposed places, and on the under surface of objects. 
Blow the powder into cracks and crevices, or underneath and behind 
objects, where it would be difficult or impossible to apply a spray. 
