Control of tabanids on horses

Insecticides that had proved effective in the laboratory against tabanids were applied in the field in Texas on horses at 0.5 g active ingredient/animal for the control of 2 groups in which Tabanus subsimilis Bellardi and T. sulcifrons Macq., respectively, were the predominant species. Permethrin gave good mortality for about 2 weeks, and SD 43775 (cyano(3-phenoxyphenyl)methyl 4-chloro- alpha -(1-methylethyl)benzeneacetate) and AC 206797 (cyano(3-phenoxyphenyl)methyl 3,3-dimethylspiro[cyclopropane-1,1’-[1H]indene]-2-carboxylate) were effective for about 1 week. Chlorfenvinphos (Compound 4072), chlorpyrifos, propoxur, toxaphene and a mixture of tetrachlorvinphos (stirofos) and dichlorvos were completely ineffective. The half-life of one formulation of permethrin (40% cis and 60% trans isomers) on hair was about 3 days; 10 p.p.m. was found to be necessary to kill tabanids, and about 2 p.p.m. to kill Stomoxys calcitrans (L.).