SPATIAL AND TEMPORAL VARIABILITY IN SEX ATTRACTANT TRAP CATCHES OF SCOTOGRAMMA TRIFOLII (LEPIDOPTERA: NOCTUIDAE) IN RELATION TO ITS BIOLOGY IN MANITOBA

Abstract

AbstractTests of intertrap variability in catches of moths of the clover cutworm, Scotogramma trifolii (Rottenberg), were conducted by placing two traps baited with an artifical sex attractant at 1 mi (1.6 km) intervals to form a grid covering 25 mi2 (64 km2) near Domain, Manitoba. The 50 traps (2/location) placed near the intersects of the grid were baited with a blend of Z-11-hexadecen-1-yl acetate and Z-11-hexadecen-1-ol. This blend was 98.6% species-specific for S. trifolii. Moth catches varied between traps and flights, but the ranking of the traps by catch was consistent during any given flight period. Up to 35 traps would be required within an area of 64 km2 (1 trap/1.8 km2) to give a population estimate within 20% of the true mean. Temperature influenced both the initiation of the flights and the number of moths caught at any given time, but there were no correlations between flights and precipitation or wind. Crop type influenced catches of S. trifolii only when moth populations were large. The catch of second generation moths averaged 9.8× the catch of first generation moths. The consistency of this relationship indicates that the annual differences in population density are controlled by variations in winter survival. The latter was linked to the induction of diapause which is governed by daylength during the larval development of the second generation.