Abstract
AbstractTests of intertrap variability in catches of moths of the darksided and redbacked cutworms, Euxoa messoria (Harris) and E. ochrogaster (Guenée), were conducted by placing two traps for each species baited with synthetic sex attractants at 1.6 km (1 mi) intervals to form a grid covering 64 km2 (25 mi2) near Domain, Manitoba. These sex attractants were 93 and 99.6% species specific for E. messoria and E. ochrogaster respectively. Moth catches varied between traps and flights, but the ranking of the traps by catch for each species was consistent during any given flight period. Variability in intertrap catches of E. messoria indicated the moths were not evenly distributed throughout the test area and consequently a sex-attractant trap system with 1.6 km trap spacing is not suitable for monitoring population levels. For E. ochrogaster four traps within an area of 64 km2 would be required to give a population estimate within 20% of the true mean. The flights of E. messoria are not related to degree days and started abruptly and at the same time each year suggesting that development may be synchronized by the summer diapause of the prepupae. The flights of E. ochrogaster were related to degree day accumulations above a threshold temperature of 12.5 °C. Crops had no apparent influence on the distribution of moth catches for either species.
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