The Use of Spray and Aerosol Formulations Containing R-1207 and Dimethoate for Fly Control on Cattle and the Determination of Dimethoate Residues in Milk1

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Abstract
The effective of R-1207 (3-chloropropyl n-octyl sulfoxide) and dimethoate for the control of flies on cattle in 1928 and 1959 was tested by means of applications with an electric-eye-controlled sprayer and a photoelectric aerosol applicator. On the average, it took 2 seconds to treat an animal and the devices were regulated to deliver from 75 to 120 ml. of spray, and from 7.8 to 10.5 grams of aerosol per animal during that time. A total of 224 applications involving the use of 19 formulations was made on four farms. Both R-1207 and dimethoate, used either separately or as mixtures, gave excellent control of the horn fly, Haematobia irritans (L.). As a spray, 2% R-1207 in Deobase was moderately efficient against the stable fly, Stomoxys calcitrans (L.), with limited effect against the face fly, Musca autumnalis De Geer, and house fly, Musca domestica L., while 1% dimethoate in Deobase had little effect on the stable fly but provided moderate protection against the latter two species. However, a mixture containing 2% R-1207 and 1% dimethoate provided effective control of nil the species concerned for 7 hours and retained a lasting residual effect against the horn fly. The addition of synergized pyrethrins permitted a considerable reduction in the concentration of both R-1207 and dimethoate without impairing the effectiveness against the horn fly and stable fly but tended to decrease the effectiveness against the face fly and house fly. Aerosol treatments containing 2% R-1207 and 0.3% synergized pyrethrins gave excellent control of the horn fly and the stable fly. In the absence of R-1207, synergized pyrethrins at 0.2% concentration failed to hold the stable fly in check effectively. In a mixture of R-1207, dimethoate and synergized pyrethrins, increases in the concentration of dimethoate consistently improved the performance against the stable fly as well as the face fly and house fly. Furthermore, dimethoate in aerosol form appeared to exert a delayed toxic action on the flies. Control of the face fly and house fly was less satisfactory, and the residual effect against these and the stable fly decreased sharply when the heads of the animals were not treated, or were treated only partially. An oil-base spray consisting of R-1207, dimethoate, and synergies pyrethins gave better results than a water-base spray with the same ingredients but the residual effect of the former diminished more rapidly, In general, the face fly appeared to be more difficult to control than the stable fly. Samples of milk from cows treated with dimethoate formulations were analyzed for dimethoate by a method developed specifically for this purpose, and sensitive to 0.01 p.p.m. Only one sample showed a measurable amount of dimethoate, possibly attributable to mechanical contamination.