Sublethal effects and mortality of tabanids (Diptera: Tabanidae) induced by fenvalerate treatment of cattle

The effect of fenvalerate spray treatments of cattle upon the feeding success and survival of tabanids (Tabanus fuscicostatus, T. lineola, T. pallidescens, T. wilsoni and T. proximus) was examined in Louisiana. Holstein cows of 350-400 kg were sprayed daily with 4-6 litres of 0.5% fenvalerate water dispersible liquid at 100-200 psi, exposed in outdoor pens to tabanids between 10.30 and 20.30 h, and rinsed with water at the end of each day. There was a reduction in feeding time for tabanids feeding on treated cows, ranging from 27.4 to 38.8%. There was also a 31% reduction in engorgement weight of T. fuscicostatus. The time that flies were allowed to feed upon fenvalerate-treated steers had no significant effect upon mortality rates or knockdown percentages.