Soil samples from North Dakota counties indicate low levels of overwintering wheat midge larvae (cocoons) for the 2026 season.

“This is the first time since the inception of the survey in 1995 that zero wheat midge cocoons were found in the fall soil survey for the overwintering cocoons of wheat midge,” says Janet Knodel, North Dakota State University Extension entomologist.

2025 was the sixth year in a row with a low number of wheat midge cocoons present in soil samples, potentially reducing farmers’ inputs for wheat midge management.  

In fall 2025, NDSU Extension agents collected 1,970 soil samples (10 cores per field) from 197 fields in 21 northern North Dakota counties. Any larval cocoons would be extracted at the NDSU Extension entomology laboratory.

Historically, wheat midge has caused significant yield and quality losses in spring and durum wheat in the northern tier of North Dakota counties from the mid-1990s through 2010.

“The fact that zero wheat midge was detected in the 2025 soil survey indicates low overwintering populations and reduced risk of economic infestation for the upcoming growing season,” says Knodel.

The number of cocoons has been low, below 500 midge larvae per square meter, for the past 10 years. Low midge pressure is tied in part to dry weather and drought conditions, which hinder the successful emergence and overwintering of larvae, according to Knodel.

Also, Fusarium head blight was more common in wheat fields in 2025, prompting farmers to spray fungicides, often tank-mixing them with an insecticide to kill wheat midge and other wheat insect pests, such as true armyworm, cereal aphids and grasshoppers. Knodel says that mixing in unnecessary insecticides isn’t good, except when insect populations are economically significant.

“With the low populations of wheat midge for the tenth year in a row,” says Knodel, “scouting for wheat midge is diminished and will be most important in continuous wheat fields.

“However, if localized wheat growing areas receive timely rains prior to heading, wheat midge emergence is favored,” advises Knodel. “On the other hand, if we remain dry, wheat midge mortality increases, and cocoons can remain dormant for several years until soil moisture returns.”

The parasitoid wasp that kills wheat midge depends on its host for survival. As expected, those wasp populations were also low due to the decline in wheat midge. For the past six years, parasitism rates have been low, ranging from 0% in 2021-2025, with 15% in 2023.

NDSU Extension Integrated Pest Management crop scouts and insect trappers also monitored for wheat midge using sex pheromone trapping during the field season. Traps with a powerful pheromone are used as an early warning system to trigger field scouting when wheat is in the susceptible stage, heading into early flowering. If more than 10 midges per trap are observed three days after heading, field scouting is initiated to determine whether a field is at an economic threshold for wheat midge.

Twenty-three pheromone traps were monitored in 19 counties in 2025. The highest wheat midge counts were concentrated in the northwest (Burke, Ward and Williams counties), the north central (Pierce County) and the northeast (Pembina County). The wheat midge parasitoid wasp also increased, with detections on sticky trap bottoms in 13 counties in 2025, up from seven counties in 2024.

According to Knodel, future efforts will focus on pheromone trapping for wheat midge and its parasitoid wasp, as trapping is more sensitive to low wheat midge densities in fields and alerts farmers to first and peak emergence and potential economic infestations. Pheromone trapping also documents the distribution of the wheat midge and its parasitoids, and it guides scouting efforts and pest management decisions for wheat midge infestations.

The North Dakota Wheat Commission supports the wheat midge larval soil survey and pheromone trapping.

NDSU Agriculture Communication – March 10, 2026

Source: Janet Knodel, 701-231-7915, janet.knodel@ndsu.edu

Editor: Dominic Erickson, 701-231-5546, dominic.erickson@ndsu.edu