The active space of Mexican rice borer (Eoreuma loftini) pheromone traps

Traps baited with a synthetic female sex pheromone blend are widely used in monitoring and management of the invasive crop pest, the Mexican rice borer, Eoreuma loftini. The active space, or attractive distance, of these pheromone traps was assessed in a 2-yr field study and a direct observational assay. The effect of intertrap distance on the trap performance was measured with hexagonal arrays of pheromone traps with a single trap in the center. Field experiments were conducted in commercial rice fields in Texas and Louisiana in 2011 and 2013. Total trap capture in 2011 was greatest in arrays with an intertrap distance of 250m, and the proportion of the total moths caught by the center trap was lower than the average proportion caught in perimeter traps at 5, 25, and 50m. In 2013, trap capture was greatest at an intertrap distance of 300m. Interference between traps was detected at an intertrap distance of 50m, but not at 100, 150, 225, and 300m. Results from field experiments indicate the active space of the pheromone traps is between 50 and 100m. This was supported by results from a controlled assay in which observers approached from downwind of the pheromone source with a caged E. loftini male and recorded the distance of first detection of the pheromone for 30 males each observed two times for a total of 60 replications. The mean distance at first detection was 47.6m, and no difference was detected between first and second exposures.