THE EFFECT OF THE WHEAT STEM SAWFLY, <i>CEPHUS CINCTUS</i> (HYMENOPTERA: CEPHIDAE), ON THE YIELD AND QUALITY OF WHEAT

Abstract

Abstract Larvae of the wheat stem sawfly, Cephas cinctus Nort, reduced the weight of grain per head by an average of 17.3% in the two spring wheats Red Bobs and Thatcher with annual reductions varying from 10.8% to 22.3%. They also lowered the protein content in Thatcher by an average of 0.6% and a maximum of 1.2%. However, because a significant loss in protein content occurred in only 1 of 6 years in Red Bobs, the effects of the larvae on protein content cannot be generalized for all varieties. The losses in weight per head resulted from a mean reduction of 11.9% in the weight of the kernels combined with a mean reduction of 1.9 in the number of kernels per head. The larvae caused the losses by feeding in the stems and by cutting them when the moisture contents of the kernels were relatively high. Annual variations in losses were attributed to the dates of the infestation, to the amount of precipitation in July and August, and to differences in dates of cutting by the larvae.