Some Methods Used in Testing Cattle Fly Sprays1

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Abstract
Existing methods of testing cattle fly sprays for repellent efficiency on the stable fly, Stomoxys calcitrans (L.), are unsatisfactory. A method, which consists essentially of making close observations on sprayed cows of previously determined fly susceptibility, gave much better results. Thirty-five selected cows were used in determining the relative efficiency of 6 fly sprays. The cows were scrubbed with soap and water, then staked individually in a pasture, being removed only for watering and milking. The normal fly susceptibility of each cow was obtained from the average of two counts of the number of flies present, made hourly from 7 a.m. till 3 p.m. for a period of 3 days. The cows were then placed in 7 groups of 5 each, the maximum difference in the number of flies per cow per count between the groups being about two. The 6 spray materials were then assigned by chance to each of 6 groups of 5 cows; the remaining group served as the control. Each cow was sprayed at 6 a.m. daily for 4 consecutive days with 2 fluid ounces of spray material applied with an electric sprayer. The fly susceptibility of the sprayed and control cows was determined as before. The results show that close individual observations of a relatively few cows of known fly susceptibility give more consistent and dependable results than less accurate observations on a large number of cows. The population of stable flies on unsprayed dairy cattle increases from 7 a.m. till about mid-day after which it tends to become stationary.

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