68 CIRCULAR 9 7 7, U. S. DEPARTMENT OF AGRICULTURE 



of tables application of the material with a paintbrush instead of as a 

 spray will avoid contamination of food, utensils, and other articles. 

 A 2-percent chlordane spray is covered by a militarv specification 

 (No. 22). 



DDT in a 5-percent spray has also been used successfully in the 

 control of cockroaches. It should be applied in the same way as a 

 chlordane spray. 



A 10-percent DDT or 5-percent chlordane dust may be blown into 

 cracks and crevices and under and around stored articles or equip- 

 ment. Dusts are recommended for treating telephonic or electrical 

 equipment, fuse boxes, or around open flames. Combined spray and 

 dust treatments are frequently used advantageously. 



A spray containing 5 percent of DDT and 2 percent of chlordane 

 is sometimes recommended for cockroach control on the theory that 

 the combination has greater immediate and more prolonged effective- 

 ness than one containing either insecticide alone. A military 

 specification (No. 22) covers a spray of this type. 



Strains of cockroaches highly- resistant to chlordane and slightly 

 resistant to DDT have been encountered. Lindane is one of the 

 materials that may be used as a substitute. One-percent sprays 

 or dusts should be applied in the same way as described for chlordane 

 or DDT. Combinations of pyre-thrum and the synergists piperonyl 

 butoxide, sulfoxide, or propyl isome may also be used. A refined 

 kerosene solution or an emulsion containing 0.2 percent of pyrethrins 

 and 1 percent of the synergist should be applied thoroughly every 

 2 or 3 weeks to all places where the roaches hide or run until the 

 infestation is under control. 



Sodium fluoride powder is still employed at times for roach control. 

 It is placed in cracks, corners, and around plumbing for the roaches 

 to walk over. It must be kept dry to be effective and allowed to 

 remain for 24 to 48 hours. 



Sodium fluoride is a white powder resembling flour and is highly 

 poisonous to humans. It is frequently combined with pyrethrum 

 or a similar quick-acting material for rapid knockdown, and colored 

 greenish gray as a safety precaution. 



FLEAS 



DDT sprays will control cat and dog fleas in or around buildings. 

 A 5-percent solution or emulsion is sprayed on the floor and the lower 

 foot or two of the walls at the rate of about 1 quart to 250 square feet. 

 Earth floors or infested ground will require about twice as much 

 spray. 



DDT dust may also be used for flea control. Infested persons 

 may be dusted with the 10-percent powder in the same manner as 

 for body lice. Where one is frequently exposed to flea infestations, 

 particularly in the presence of flea-borne plague or murine typhus, 

 treatment of the clothing with a flea repellent is recommended (see 

 p. 76). 



For control of fleas on dogs a 10-percent DDT or a 1-percent 

 lindane powder should be dusted into the hair along the back and 

 neck. For cats, pyrethrum or derris powder rather than DDT or 

 lindane should be employed as they are less hazardous to this animal. 



