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Wheat Stem Sawfly in NC ND (08/16/18)

I've had several other calls on wheat lodging from wheat stem sawfly in Berthold area in Ward County (Andrew Green, NDSU Wheat breeder), Mohall area in Renville County and Souris area in Bottineau County.

Wheat Stem Sawfly in NC ND

I've had several other calls on wheat lodging from wheat stem sawfly in Berthold area in Ward County (Andrew Green, NDSU Wheat breeder), Mohall area in Renville County and Souris area in Bottineau County. The dry conditions in these areas probably aggravated the wheat stem sawfly problem. The best strategy is to swath wheat if more than 15% of stems are infested with wheat stem sawfly larvae. Producers should swath sawfly-infested wheat as soon as kernel moisture drops below 40% to save infested stems before they lodge. Lodging occurs at 30-35% moisture in infested sawfly stems. This requires field surveys to determine infestation levels. Infested stems have a reddish-brown spot below the second or third node. Examine 50 consecutive stems in a drill row from at least two sites (one near the field margin, another near the center). Determine the percent of stems infested at each site. If producers decide to swath grain, use a high swathing height to conserve the parasitoids that attack wheat stem sawfly. Research from Montana State University has shown that taller residue (at least the lower ⅓ of the plant) is better for conserving the parasitoids.

If 10 to 15% of the crop was cut by sawfly during the current field season, a solid-stemmed variety of wheat is recommended for the upcoming field season. I would recommend a high-yielding, solid-stemmed (sawfly resistant) variety like Mott, or one of the Canadian or Montana varieties (see NDSU Extension Integrated Pest Management of Wheat Stem Sawfly in ND for listing of solid-stemmed varieties).

Insecticides DO NOT work for control of adults and are a waste of time and money. Insecticides actually make the situation worst since broad-spectrum insecticides kill the beneficial wasps that attack and decrease populations of wheat stem sawfly. These parasitic wasps have a moderate parasitism rate, >30% in ND.

Crop rotation to non-host crops (oats, flax, sunflower, canola, pulse crops, soybeans, legumes, and to a lesser extent barley, rye) will break the insect’s life cycle and help reduce populations of wheat stem sawfly.

 

Janet J. Knodel

Extension Entomologist

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