Crop & Pest Report


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Too Early for Wheat Midge Control (06/27/19)

Emergence of the male wheat midge has just begun at 1300 Accumulated Degree Days (ADD) using a 40⁰F base temperature.

Emergence of the male wheat midge has just bent.11egun at 1100 Accumulated Degree Days (ADD) using a 40⁰F base temperature. The male emerges before the female wheat midge. Females start to emerge at 1300 ADD, at 1475 ADD about 50% emerged, and at 1600 ADD about 90% emerged. See wheat midge NDAWN map below. The hot weekend forecast with the 90⁰F will push the degree-days to climb into 1300+ ADD, so the female wheat midge emergence will start to emerge.

Some growers with early planting dates have spring wheat fields that are near late heading-flowering for scab control. However, it is too early to pull the trigger for wheat midge management. For pest management, we are more concern with the female wheat midge that lays the eggs on wheat heads. The optimal insecticide application timing for wheat midge control is between late heading through early heading. After 50% flowering, the female wheat midge is not attracted to the wheat heads for egg laying, and the beneficial parasitic wasp is emerging which provides natural control of wheat midge eggs and larvae.

What was your spring wheat planting date? Planting dates correlate to the risk of wheat midge infestation. Early planted spring wheat (prior to 200 wheat midge ADD) will head before wheat midge emergence, and late-planted wheat (after 600 wheat midge ADD) will head after peak emergence of wheat midge. Spring wheat planted between 200 and 600 wheat midge ADD will head at the time of peak wheat midge emergence and will be higher risk. The NDAWN DD model for wheat midge is setup to integrate wheat planting dates with susceptibility to wheat midge emergence and it calculates the risk for wheat midge infestation. Growers and crop consultants can assess the NDAWN Wheat midge DD model at: Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether it is susceptible to wheat midge infestation, as well as how far along the wheat midge emergence is, such as, 50% females emerged.

Wheat fields that are susceptible to wheat midge infestation should be confirmed by scouting for economic populations of wheat midge. Wheat midge scouting is conducted at night when temperatures are greater than 59⁰F and the winds are less than 6 mph. Use a flash light and slowly scan the heads of wheat plants for wheat midge adults (small orange fly), counting the number of adults per head, and then calculate an average number of adults per head. The economic thresholds for wheat midge are: one or more wheat midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

Consult the NDSU Extension publication E1330 (revised) Integrated Pest Management of the Wheat Midge in ND for more information.



Janet J. Knodel

Extension Entomologist

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