\ ANNUAL REPORTS 01 DEPARTMENT 01 AGRICULTURE, 1049 
percent of DDT (by weight) has remained undamaged after 18 
months 1 exposure to heavy Infestations of fabric insects. The Brsl 
year's tests conducted for the Army indicate that this insectic 
better protection to Btored woolen cloth than the naphthalene treat- 
• ik.u being used by the armed forces. It" future tests confirm 
these results and DDT Is substituted for naphthalene, much less cloth 
will be lost through insect damage, at a tremendous .-a\iiiL r In cos( of 
i be i reatment. 
Although DDT gives the best protection to cloth from dan 
chlordane and benzene bexachloride are more effective In killing 
fabric insects. Although generally less effect ive, methoxychlor, Tl >K. 
and toxaphene also show considerable promise. 
INSECTS AFFECTING LIVESTOCK 
Toxicology of Insecticides W hen Applied to Livestock 
Investigations on various aspects of the toxicology of Ins I 
when applied to livestock were continued with funds authorized under 
the Research and Marketing Act of L946. This work was done in 
cooperation with the Bureau of Animal Industry, the Bureau of Dairy 
Industry, the Texas Agricultural Experiment Station, the Food and 
Drug Administration, and the insecticide industry. Certain phases 
of this cooperative work are also discussed in the current Annual Im- 
port of the Chief of the Bureau of Animal Indus! ry. 
Safer insecticides replace DDT for use on dairy farms 
This Bureau has changed it- recommendations for the control of 
insects on milk cows and In dairy barns. This action was taken as a 
precautionary measure, because in the spring of L949 the Food and 
I > 1 1 1 ir Administration announced that the presence of any amount of 
DDT in in ilk won Id becont rary to tin- Food. Drug, and Cosmetic Act 
Studies by this Bureau in cooperation with the Bureau of Animal 
Industry, the Bureau of Dairy Industry, and the Texas Agricultural 
Experiment Stat ion have shown that small quantities of DDT appear 
in milk of cows that bave been treated with tin- insecticide and can 
sometimes be detected in milk following its ordinary use in dairy barns 
for fly control. 
The Bureau recommends methoxychlor and pyret hrum insecticides, 
particularly a mixture of pyrethrum with piperony] butoxide, for 
application to dairy animal-. Methoxychlor i- more effective and 
economical for controlling horn flies and lice, but the pyrethrum in- 
secticides appear to give better protection against attack by stable 
flic- and horse Hie-. 
Methoxychlor and lindane < hen /cue bexachloride containing at Least 
99 percent of the gamma isomer) are suggested a- residual sprays, and 
pyrethrum and an organic thiocyanate a- Bpace Bprays lor By control 
in daii\ barns and other buildings where milk i- processed. Experi- 
ments showed that methoxychlor was usually effective against house 
flies for I to 2 months when applied at the rate of 200 milligrams per 
Bquare foot. In some areas, bowever, flies that had developed a 
marked resistance to DDT were also more ditliewli t«> control with 
