Comparison of adult emergence of wheat stem sawfly from material overwintered in the field and the laboratory

Abstract

We examined whether collection time (pre-winter vs. post-winter) influenced adult and female emergence success and body mass of wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), from four Montana populations in [2005][2006]. Adult emergence was generally higher from post-harvest material in post-winter collections but varied widely among populations. No significant effect of collection time on male-biased adult emergence from postharvest residue collected near Conrad (37% vs. 31%) was detected, although adult emergence was greater for post-winter collection than for pre-winter collections from sites near Havre (90% vs. 81%), near Amsterdam (88% vs. 41%), and near Loring (67% vs. 0%); these three populations had a bias towards adult females that exceeded 2:1. Adult body mass was greater for postwinter-collected males (30% higher) and females (15%) only from near Amsterdam. Diapausing C. cinctus larvae overwintering under field conditions had better adult emergence, and spring collection is recommended in order to minimize time allocated to acquiring C. cinctus populations for research.