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Wheat Midge Forecast for 2019 (07/04/19)

Soil samples in North Dakota indicated low levels of overwintering wheat midge larvae (cocoons) for the 2018 season.

Soil samples in North Dakota indicated low levels of overwintering wheat midge larvae (cocoons) for the 2018 season. A total of 2,000 soil samples were collected by NDSU county Extension agents from 21 counties in the fall of 2018 to estimate the regional risk for wheat midge in the 2019 field season. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

Less than one percent of the soil samples had economic population densities of wheat midge (greater than 500 midge larvae per square meter) this past year.  A hot spot was located from one soil sample taken in the central area of Burke County and one from Ward County in North Dakota. The majority of the soil samples, 84 percent, had zero wheat midge cocoons, which is a new record low for the wheat midge larval survey since it started in 1995.

This is the second year in a row with good news for North Dakota wheat producers as low levels of midge larvae will reduce the likelihood that insecticide will be needed for wheat midge control in wheat in 2019.

Wheat midge populations ranged from zero to 607 larvae per square meter, with an average of 17 larvae per square meter in 2018. Wheat midge populations were slightly higher in 2017 and 2016, ranging from zero to 1,321 in 2017 and 2,071 larvae per square meter in 2016. Other areas with low wheat midge populations (200 to 500 larvae per square meter) occurred in one small pocket in west-central Ward County. These population levels are still considered noneconomic and low risk for wheat midge.

The drought in the northwestern and north-central areas of North Dakota probably caused high mortality to wheat midge for the last two years. Larvae are susceptible to dryness and require dew or rain to drop out of the wheat heads and dig into the soil to overwinter as cocoons. However, areas with more than ¾ inch of moisture in mid- to late June will have more favorable conditions for wheat midge emergence this year.

It is always good integrated pest management to scout for wheat midge adults during emergence, especially if wheat fields are in the heading to early flowering (less than 50 percent flowering) crop stage, the susceptible time period for wheat midge infestation.

The North Dakota Wheat Commission supports the wheat midge survey. Wheat midge maps and Ag News releases are posted on the NDSU Extension Entomology website.

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Janet J. Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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