Dry Conditions in 2023 Keep Wheat Midge Forecast Low for 2024

“Soil samples in North Dakota indicate low populations of overwintering wheat midge larvae (cocoons) for the 2024 season,” says Janet Knodel, North Dakota State University Extension entomologist. “This is good news for North Dakota wheat farmers, reducing their inputs for wheat midge management.”

A total of 2,060 soil cores were collected from 22 counties in the fall of 2023 to estimate the statewide risk for wheat midge in the 2024 wheat growing season. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

Wheat midge was positive at only 20 field sites (10% of the sites) in eight counties including Cavalier, Nelson and Towner Counties in the northeast, Bottineau, Pierce and McHenry Counties in the north-central region, McLean County in the west-central region, and Ward County in the northwest. These sites had low levels of wheat midge cocoons (1-200 cocoons per square meter) which does not cause yield loss in spring wheat. No soil samples had moderate or high cocoon densities of wheat midge (201 to over 800 midge larvae per square meter) which could cause economic losses in spring wheat.

“The majority of the soil samples had zero wheat midge cocoons in the soil for the past four years (90% in 2023, 97.5% in 2023, 95% in 2021 and 86% in 2020),” says Knodel. “We believe that the populations of wheat midge are low due to the extended drought in northern North Dakota over the past several years. Populations could return to higher levels once the drought subsides and we return to more normal rainfall.”

Dry conditions will delay when wheat midge larvae drop out to the soil for overwintering in late summer. During drought, larvae will remain in the wheat head and are often harvested with the grain, ending up in the grain truck or bin. Dry soil conditions also increase wheat midge mortality by making it difficult for the larvae to dig into the soil for overwintering and by exposing them to predators on the soil surface.

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