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The destruction of old grubs could be ascertained beyond 
doubt by their soft condition after about 3 days. The 
appearance of fresh grubs -as not noticed until about 
4 weeks after the treatment. This effect was obtained 
only after e double treatment at an interval" of 1 to 
3 days and only when very finely ground derris roots 
'"ere used, but more than 90 percent control -as obtained 
with only one thorough treatment. The results obtained 
with solutions made from coarsely chopped root were not 
nearly so good. 
The same Bureau (299) in 1932 stated that the Warble Fly Com- 
mittee of the Leathersellers' Company ( 170 , 171 ) , London, reported 
that experiments <"ith derris preparations had been conspicuously 
successful. 
According to the Warble Fly Committee ( 170 ) in 1930, more than 
10,000 cattle in Worcestershire, England, were treated with the 
Polvo wash. In 1932 the Leathersellers' Company ( 171 ) published 
information on tests carried out at various places in England, Ire- 
land, and Scotland during 1931. Derris was tried in the following 
forms: Dry derris oowder, derris-soap wash, Polvo, Katakilla, 
Cooper's Warble Wash, and Cooper's Warble Powder. In northern Ire- 
land tests on 805 cattle shoved that 99.5 percent of the warbles 
were killed by four applications of the derris-soap wash (l lb. 
Polvo, 1/4 lb. soft soap, 1 imp. gal. water). In tests in 
Caernarvonshire dry derris powder killed 98 percent of the warbles. 
Burton (46) in 1934, in a lecture on the warble fly, referred 
to the conclusion of the Leathersellers 1 Warble Fly Committee that 
a derris-soap wash, applied to the marble lumps with a Mrly stiff 
brush wa S an economical, efficient, and practical way of killing 
the grubs in the animal's back. 
Petti t ( 232 ) in 1932 described the method of applying Gusenol 
(a proprietary derris product) to cattle for the control of Hyooderma 
larvae. 
Townsend ( 276 ) in 1932 gave directions for the use of derris 
powder against warbles as follows: Derris 1/2 pound; soft soap 1/4 
pound., water 1 imperial gallon, applied by hand with a cloth or brush- 
or with a sguirt can. Its action is due to the mild poison it contains 
and to the fine particles stopping up the breathing holes of the grubs. 
Baudet (18) in 1933 reviewed the results of tests by G'otze with 
derris-soap wash and by Peter to control ox warbles. Peter did not 
obtain so good results from the use of Cooper's Warble Powder as 
English authors described. 
Baudet and DeBoef (20) in 1933 reported on the control of ox 
warbles with a water extract of derris made by soaking 1 kg. of derris 
powder containing 2 percent of rotenone in 9 liters of water for 24 
