Carabid Predators of the Wheat Midge (Diptera: Cecidomyiidae) in Saskatchewan

Abstract

Carabid predators of the wheat midge, Sitodiplosis mosellana (Gehin), in northeastern Saskatchewan were determined by immunoelectro-osmophoresis. Fourteen carabid species in the genera Agonum, Amara, Bembidion , and Pterostichus were identified as having fed on wheat midge larvae in the field. Adult Bembidion quadrimaculatum L., Bembidion obscurellum Motschulsky, Agonum placidum Say, and Pterostichus corvus LeConte killed 9, 15, 43, and 48 midge larvae per beetle per day, respectively, in laboratory studies without alternative prey. Estimates of daily predation in the field for all carabid species combined ranged from <1 to 86 midge larvae/m2. Midge larvae were susceptible to predation during June after breaking larval diapause and during August when they were moving from the wheat ( Triticum aestivum L.) heads to the soil where they overwinter in cocoons. Although carabid predation alone was not considered to have a major effect on reducing midge populations, it does contribute to overall mortality and plays a role in the natural control of this pest. Furthermore, total predation by carabids may have been underestimated because sampling may have captured mainly diurnally active species.