ABUNDANCE AND MORTALITY OF OVERWINTERING HELIOTHIS SPP.

Abstract

Field surveys, field cage studies, and records of light trap catches wewe used to follow the abundance and mortailty of Heliothis punctiger (Wallengren) and H. armiger (Hübner), through the autumn, winter and spring, over a 9 year period. Both the timing of spring emergence and magnitude of moth flights of H. armiger were consistent with priotr observations of autumn and winter populations in the Namoi Valley. Subsequent abundance was greater in 2 seasons when wheat anthesis and spring emergence coincided, but overwintering populations declined considerably during the study period. Although H. punctiger was not usually abundant in the area during autumn and winter, earlier and larger moth flights of that species than of H. armiger occurred in spring, leading to heavier infestation of crops and pastures. Apparent anomalies in the early spring abundance of H. punctiger may be explained by migration from other areas, or early emergence of the non‐diapausing fraction of the population. Substantial parasitism of overwintering H. armiger by Ichneumonidae and Tachinidae was recorded, while mechanical destruction of pupae during cultivation of crop residues also caused heavy mortality. Copyright © 1983, Wiley Blackwell. All rights reserved