During the past 12 years the Entomology Research Division has placed major em- 
phasis on the insecticide residue problems in relation to meat and milk. Much of this 
research has been carried forward by the Kerrville, Tex., livestock insect laboratory 
in cooperation with the Animal Disease and Parasite Research Division. Many formal 
cooperative programs have been jointly financed by industrial companies and the De- 
partment for the purpose of studying the relationship of contemplated insecticide use for 
livestock and forage pests and the appearance of insecticide residues in meat and milk. 
This subject will be treated more fully by Westlake and San Antonio and Radeleff and 
Bushland in the papers prepared for this symposium. 
As a result of such investigations, clearance has been obtained for a number of in- 
secticides for application to meat animals and for some to be applied to dairy animals. 
However, the research has also yielded residue data which led to the discontinuance of 
recommendations for several compounds important in dairy production. Today the insec- 
ticides and repellents we have for protection of dairy cows from most insects and ticks 
are no better than they were 25 years ago. 
The use of systemic insecticides for the control of cattle grubs has been pioneered 
by the Kerrville, Tex., and Corvallis, Oreg., laboratories of the Entomology Research 
Division. Through the cooperation of these laboratories, industrial research groups, 
many State agricultural experiment stations, and the Animal Disease and Parasite Re- 
search Division two animal systemics, ronnel and Co-Ral, are now in practical use 
for cattle grub control and other more promising materials are under investigation. 
BASIC DEVELOPMENTS IN CHEMICAL RESEARCH 
I have said little about the more basic achievements in the chemical aspects of 
insecticide development and use. It is not possible in this general treatment of the sub- 
ject to properly credit the many chemists inindustry and in Federal and State institutions 
who have discovered and developed the many and varied insecticides, attractants, and 
repellents in use today. Most of the materials in use have come from industrial labora- 
tories, but public-supported institutions, including the Citrus Experimental Station, 
Riverside, Calif., the University of Illinois, andthe Pesticide Chemicals Research Branch 
in the ARS Entomology Research Division, have made valuable contributions in the de- 
velopment of new materials. Industry has borne most of the cost of early research to 
establish the biological effectiveness of new compounds and to obtain basic information 
on their toxicity to animals. However, the cooperation of entomologists and chemists in 
State and Federal laboratories throughout the country has made it possible to obtain 
necessary information on the biological effectiveness of compounds for specific insect 
pests and to obtain residue data needed to establish tolerances. 
In spite of the need for additional information on the nature and fate of insecticides 
in raw agricultural products, the progress made through this cooperative effort by many 
individuals has been outstanding and has led tothe establishment of over 2,000 tolerances 
involving a wide variety of insecticides, and commodities. 
The Pesticide Chemicals Research Branch of the ARS Entomology Research Division 
has borne the brunt of the Department’s responsibility in meeting the insecticide residue 
problem. In addition to this phase of the Branch program, however, some basic studies 
on the relationship of chemical structure and biological activity have been undertaken 
which have led to several important contributions. Much of the development in the field 
of synergists for pyrethrum stems from early researchon the structure of the synergistic 
components in sesame oil (Haller, et al., (2)). The elucidation of the chemical structure 
of the pyrethrins (LaForge and Haller (6), LaForge and Barthel (7), and LaForge and 
Soloway (8)) and subsequent synthesis of allethrin and other pyrethrum-type compounds 
(Schechter, et al. (10)) represent important achievements. The best insect repellent 
available today, "diethyl toluamide was discovered by chemists in this Branch. The re- 
search on synthetic attractants for Mediterranean and melon fruitflies already referred 
to has been highly productive. 
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