Circular 21 - Insecticides and Subsidiary Materials 32 
To be acceptable for use, a fly spray 
of this type should meet the requirements set 
forth in the publication referred to above. 
Briefly, these requirements specify that the 
killing pov/er of the liquid spray shall be 
determined by the Official Peet-Grady Method 
in conjunction with the Official Test Insec- 
ticide of the National Association of Insec- 
ticide and Disinfectant Manufacturers, Inc. 
In 19^0 the Official Test Insecticide (O.T.I.) 
was an oil pyrethrum spray containing 0.113 
percent pyrethrins. Insecticides are rated 
according to their killing power as follows: 
Q^g^^Q Percent kill after 24 hours 
as compared to the 0. T. I. 
AA 16 (or more) greater 
A 5 to 15 greater 
B 5 less to 5 greater 
In addition, when used in the customary manner 
the spray shall be harmless to man and warm- 
blooded household animals, shall not stain 
fabrics, wallpaper, and general household 
furnishings, shall not contaminate closed 
packages of commonly found food materials, 
shall not corrode metals, shall have no 
objectionable odor, and shall have a flash 
point of not less than 125° F. when tested 
in the Tagliabue closed cup. Certain com- 
binations of highly refined petroleum 
distillates with pyrethrum extracts, derris 
extracts, or organic thiocyanates meet these 
standards and form the basis for numerous 
commercial fly sprays. 
