A Survey of Five Stem-Feeding Insect Pests of Wheat in the Northern Great Plains

Abstract

The wheat stem sawfly, Cephas cinctus Norton, the wheat stem maggot, Meromyza americana Fitch, the Hessian fly, Mayetiola destructor (Say), the wheat jointworm, Tetramesa tritici (Fitch), and the wheat strawworm, Tetramesa grandis (Riley), have long been considered wheat pests in the northern Great Plains. This paper reports results of surveys for these pests conducted over 3 yrs in parts of Montana (10 counties), North Dakota (14 counties), South Dakota (1 county), Nebraska (4 counties) and Wyoming (1 county). Fields were randomly selected and a mean of 191 stems were sampled from each field. The percentage of stems infested with each pest was recorded. The percentage of parasitized wheat stem sawfly larvae also was noted. The wheat stem sawfly, wheat stem maggot, and Hessian fly were the most commonly encountered pests, recorded in nearly every county. Wheat stem sawfly density was twice that of wheat stem maggot (7% vs 3.2%) in infested fields. Wheat stem sawfly densities exceeded 10% in 4 counties: Daniels and Wibaux in MT, Golden Valley, ND and Goshen, WY. Wheat stem sawfly parasitism was low and positively correlated with sawfly infestation. Wheat stem maggot infestations were low (<11% for all fields), averaging 3.2% among infested fields. Hessian fly densities were much lower (2.2% among infested fields) than reported elsewhere in the U.S. The wheat jointworm and strawworm were absent from most fields and only occasionally found at low levels (<1% and <3.5% respectively, among infested fields). This information will help to prioritize wheat insect pest management research and extension programs in this region.