PHENOLOGY OF THE EUROPEAN CORN BORER (OSTRINIA NUBILALIS) IN ALBERTA

Abstract

AbstractDifferences in phenology were observed between two populations of Ostrinia nubilalis (Hbn.) in Alberta. In the South Saskatchewan River valley, borers pupated and emerged 3–6 days earlier than on the plains. This was not simply a function of different microclimates because median pupation occurred at 331 degree-days (DD) for plains populations and at 490 DD for valley populations. First-generation flight extended from the last week in June until the 1st week in August. Flight peaks in 1983 occurred on 8 July in the valley and on 14 July on the plains. Flight was delayed in 1984 by cold nightly temperatures. In 1983 valley populations had a partial second generation, with a flight peak in late August. Mean pupal mass was significantly less for plains populations than valley populations. Transplant experiments demonstrated that these differences reflected mainly environmental influences. During spring 1984, mean larval mass in the two populations did not differ until early June, when both mean wet and dry mass of valley larvae increased significantly but those of plains larvae did not change. This variability of phenotypes contributes to the colonizing ability of the European corn borer.