Experiment Station Record, Volume 92, January-June, 1945 Page: 82
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82 EXPERIMENT STATION RECORD [Vol. 92
livestock sprays by the skin reactions of dairy cows in the first of the 2 yr. of this
study included a widely used commercial preparation, two widely used base oils, and
several combinations of toxic ingredients in one of the base oils. Each animal was
sprayed daily for 30 consecutive days at about 40 cc. per 1,000 lb. of live weight;
even the worst skin reaction was not serious, but noticeable differences were observed.
In the second year, comparisons of 17 base oils were made under more
controlled conditions by spraying four selected areas on the same animal with 4
different oils, applications also being made daily for 30 days. Spraying 5 cc. on 2
sq. ft. of animal failed to reveal differences in the oils (two exceptions); use of
10 cc., however, brought out marked differences among them. Observations on the
thirtieth day revealed that 8 of the oils' were noticeably more harmful than the other
9. The best index of the effect on the skin was found to be the unsulfonated residue
content of the oils; those containing 92.5-100 percent included all the most satisfactory
oils (one exception), while oils containing 87.5 percent or less gave the
most unsatisfactory skin reactions. Contrary to published statements, the Saybolt
viscosity of au oil did not prove a reliable index of skin reaction in these tests.
Factors other than skin tests would need consideration in selecting base oils for
livestock sprays, but these findings show the possibility of minimizing harmful
effects to the skin by proper choice of oils.
Comparative toxicity under barn conditions of livestock type fly sprays made
from various combinations of toxic ingredients and base oils, F. W. ATKESON,
R. C. SMITH, A. R. BORGMANN, and H. C. FRYEl. (Kans. Expt. Sta.). (Jour.
Econ. Ent., 37 (1944), No. 3, pp. 428-435).-The 16 livestock sprays compared for
relative toxicity in dairy barns included 2 commercial sprays and 14 of known
composition; each was used at the rate of 1 cc. per 36 cu. ft.-approximately half
the amount prescribed for the Peet-Grady test. The following conclusions are
believed justified: In barn spraying tests knock-down counts need not be taken
after 5 min. In general, the 16 sprays varied widely in knock-down efficiency, but
the top 5 sprays were about equal; highly significant (odds 99 : 1) differences existed
between the better and the poorer sprays. Lethane and Thanite were among the
best toxicants in knock-down; pyrethrum was least so but when fortified with D.
H. S. Activator it was among the best at concentrations of 3.75 percent or more of
a 20 : 1 concentrate. There was some indication that low viscosity oils are superior
in knock-down effect to those of higher viscosity. The 16 sprays varied almost as
much in killing as in knock-down efficiency, but the 4 top-ranking ones were equal.
Thanite was the best in killing power of any single toxicant used in base oil; in
water it was less efficient, but the difference between it and the 4 lowest ranking
base oil sprays was highly significant. Pyrethrum and Lethane were among the
least efficient in killing power, but when D. H. S. Activator was added to pyrethrum
sprays containing 3.75 percent or over of a 20 : 1 concentrate they ranked among
the most efficient. Differences in results were obtained with sprays made from
different base oils, but the available data do not reveal which of the oil properties
were responsible. Three of the 4 best sprays in kill were among the 5 best in knockdown,
and 3 of the 4 poorest ones in kill were also among the poorest in knock-down;
others varied widely in relative rank for kill and knock-down. The results of this
study indicate the importance of a lethal dosage at the time of knock-down and
show that the percentage of kill is a better measure of the toxicity of a livestock
spray than that of the knock-down.
Activation of pyrethrins in fly-sprays, W. A. L. DAVID and P. BRACEY (Nature
[London], 153 (1944), No. 3889, pp. 594-595).--An accepted method of "stretching"
limited supplies of pyrethrins is to add to the spray a small proportion of a
material which, though not in itself insecticidal, yet has the property of making the
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U.S. Department of Agriculture. Agricultural Research Administration. Office of Experiment Stations. Experiment Station Record, Volume 92, January-June, 1945, book, 1947; Washington. (digital.library.unt.edu/ark:/67531/metadc5064/m1/95/: accessed January 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.