CALCULATING ECONOMIC INJURY LEVELS FOR STABLE FLIES (DIPTERA, MUSCIDAE) ON FEEDER HEIFERS

A procedure for calculating the economic injury levels for stable flie s, Stomoxys calcitrans (L.), on feeder heifers was developed from redu ction of average daily weight gain-stable fly population level data in 8 independent replicated experiments over 17 yr. A negative exponenti al was fitted to the data using nonlinear regression. Regression coeff icients were then used to derive a simple predictive equation for calc ulating the economic injury level in relation to cost of controlling s table flies in the feedlot, and the market value of heifers. Examples for calculating the economic injury level under practical feedlot situ ations are presented. Also included are recommendations for a simple r andom sampling design for flies feedlots.