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SPATIAL AND TEMPORAL VARIABILITY IN SEX ATTRACTANT TRAP CATCHES OF SCOTOGRAMMA TRIFOLII (LEPIDOPTERA: NOCTUIDAE) IN RELATION TO ITS BIOLOGY IN MANITOBA1

Published online by Cambridge University Press:  31 May 2012

G. L. Ayre
Affiliation:
Agriculture Canada
W. J. Turnock
Affiliation:
Agriculture Canada
D. L. Struble
Affiliation:
Agriculture Canada

Abstract

Tests 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.

Résumé

Des essais sur la variabilité (d'un piège à l'autre) des captures d'adultes du vergris du trèfle, Scotogramma trifolii (Rottenberg), ont été effectués en plaçant deux pièges, appïatés d'un attractif sexuel artificiel, situés à intervalles de 1 mille (1,6 km) de façon à former une grille couvrant 25 mi2 (64 km2) près de Domain (Manitoba). Les 50 pièges (2 par endroit) placés près des points d'intersection de la grille ont été appâtés au moyen d'un mélange d'acétate de Z-11-hexadécène-1-yl et de Z-11-hexadécène-1-ol. Ce mélange est spécifique à 98,5% pour S. trifolii. Les captures d'adultes varient selon les pièges et les vols, mais le classement des pièges par capture est homogène au cours d'une période de vol donnée. Il faut jusqu'à 35 pièges sur une superficie de 64 km2 (1 piège/1,8 km2) pour permettre d'estimer la population située dans un écart de 20% de la moyenne vraie. La température influe à la fois sur le début des vols et sur le nombre de papillons capturés à un moment donné, mais on n'observe aucune corrélation entre les vols et les précipitations ou le vent. Le type de culture influe sur les captures de S. trifolii, seulement lorsque les populations d'adultes sont considérables. La capture de papillons de la seconde génération est en moyenne 9,8 fois plus élevée que celle des adultes de première génération. La constance de ce rapport indique que les différences annuelles observées dans la densité de la population sont régies par les variations du taux de survie en hiver. Celui-ci est lié au déclenchement de la diapause, lui-même conditionné par la longueur du jour au cours du développement larvaire de la seconde génération.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1982

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