348                 The Possibilities of Cattle Fly Sprays in India

As for the cost of the spray, this was calculated at slightly less than six
pies (exclusive of freight) per spray of 60 c. c. It is, however, very probable
that a much smaller quantity would prove equally effective, because the re-
sults of similar trials carried out by Freeborn and Regan [1932], in U.S.A.,
appeared to them to point to the conclusion that, in order to obtain an average
repellent efficiency of 80 per cent over a period of 21 hours with petroleum
oils containing pyrethrum, pine oil or both, it was necessary to apply
'approximately 250 c. c. of spray per 1,000 lb. of cow ' and, furthermore,
according to the same workers, 20 c. c. of a very light spray is a complete
coverage for a cow weighing 1,000 lb. On the basis of these calculations, 30
c. c. of the ' Pyrocide 20 ' spray should be a good coverage for cows of
Sahiwal breed and at the same time give a fairly high repellent efficiency for
a period of ten hours (7 A.M. to 5 P.M.). The cost, however, would obviously
require to be further reduced if the use of cattle fly sprays is to find a ready
place in dairy practice in India.

                         SUMMARY AND CONCLUSIONS

The two factors which impose a limitation on the value of repellent sprays
in combating cattle flies in India are their liability to cause burning of the
skin and their high cost compared with the benefit they may be expected to
accrue from their use in the case of cows of low milk yield. The paper dis-
cusses the possibility of overcoming these difficulties in the light of the results
of a series of fly repellency tests carried out in one of the Government cattle
farms in the United Provinces. In the course of these tests, it was observed
that a spray consisting of high speed Diesel oil, ' Pyrocide 20 ' (a concen-
trated extract of pyrethrum flowers) and pine oil, when applied on Sahiwal
cows for 21 consecutive days, during October, did not produce any burning
or scurfing of the skin, although the spray proved to be very effective against
Musca crassirostris and Lyperosia exigua, which were at the time the two
prevalent species of biting flies on the farm. About 60 c. c. of the fluid was
used for each spray and the cost of this quantity was slightly less than six
pies. In view, however, of the results recorded in this field by workers in
other countries, it is probable that a much smaller dose would prove equally
effective. The use of the spray was also found to result in an appreciable
increase in the yield of milk.

                                      REFERENCES

Bishopp, F. C. (1931). U. S. Dept. Agric. Farmers' Bull. 1097, 17
Freeborn, S. B., & Regan, W. M. (1932). J. Econ. Ent. 25, 167-74
––––––––––––––––––––& Folger, A. H. (1925). J. Econ. Ent. 18, 79-90
(Cited by Melvin, Roy in J. Econ. Ent. 25, 1154-64 ; 1932)
Pearson, A. M. (1935). Bull. Del. Agric. Expt. Sta. 196, 63 (Abstr. in Rev.
App. Ent., B, 24, 304-5 ; 1936)
––––––––,Wilson, J. L., & Richardson, C. H. (1933). J. Econ. Ent. 26, 269-74
Sinton, J. A., & Wats, R. C. (1935). Rec. Malar. Surv. Ind. 5,275-306