insecticides thoroughly to all secluded places and cracks so that, no 
matter where a roach tries to hide, it will come in contact with the 
residue. Sometimes it is difficult or impossible to treat all the hiding 
places. Therefore, you should also treat exposed surfaces. When the 
roaches come out at night in search of food and water, they will then 
have to walk over a treated surface. Roaches are not killed immedi- 
ately by contact with insecticide deposits, but will die within a few 
hours after sufficient exposure to them. 
Roaches are fairly easy to control in most homes. In many commer- 
cial establishments control may be more difficult. If you continue to 
have trouble after following the suggestions given, you may wish to 
call in a good pest-control operator. The better operators have the 
equipment and training necessary to do a good job. They also have 
the background of experience required to discover and deal with 
unusual or complicated conditions. 
PREFERRED INSECTICIDES 
Many different preparations are sold for roach control. The most 
satisfactory ones are discussed in this section. 
Chlordane 
Chlordane is one of the most effective insecticides now available 
for roach control. It is a new insecticide with residual properties. 
Chlordane should be used as a 2-percent spray or a 5-percent powder. 
When it is applied as a residual spray, the oi] or water base evaporates 
and leaves an invisible film, which remains effective on the treated 
surface for several weeks and continues to kill roaches that walk over 
it. The liquid spray is the form most commonly used. It can be 
obtained as an oil solution or a water emulsion. You can also buy 
a 50-percent chiordane emulsion concentrate, which should be mixed, 
1 part with 24 parts of water, to make a 2-percent spray. Although 
the emulsion has a milky-white appearance, the spray will not stain 
surfaces that would not be harmed by water. 
DDT 
DDT insecticides applied thoroughly are also effective against all 
kinds of domestic roaches, but less so than chlordane. Some satisfac- 
tory roach insecticides contain both chlordane and DDT. Liquid 
sprays should contain 5 percent of DDT and powders should contain 
10 percent. The 5-percent DDT spray is readily available as an oil 
solution. Emulsion concentrates are also available, to be diluted with 
water before being used. The residue from a DDT solution or 
emulsion is in the form of numerous tiny crystals that are almost 
invisible on most surfaces. The residue remains effective from several 
weeks to several months. 
Pyrethrum 
In situations where other insecticides might create a hazard to 
humans, pets, or food, pyrethrum insecticides may be used for safe and 
effective roach control. Pyrethrum was formerly applied directly as 
a contact insecticide for immediate effect, but it is not always possible 
