Green Acres

By Tyler Lane

The Mountaineer of Big Sandy, Montana

Wheat Stem Sawfly Management Questions and Answers

1. Are all oat varieties resistant to wheat stem sawfly? MSU Entomologist David Weaver responded with the following: I am not aware of any survival of wheat stem sawfly larvae in oat. If the egg is laid in the oat stem, the larva will die.

2. Why are oats a great trap crop to manage wheat stem sawfly? Oats are a great trap crop for wheat stem sawfly management because oats can be used as a form of pest population management. Other trap crops like Willow Creek winter wheat do not manage wheat stem sawfly numbers because the wheat stem sawfly larva survive in the Willow Creek stems.

3. What is a trap crop? A trap crop is attractive to the pest. The trap crop is seeded around the border of the field to protect the susceptible crop on the inside of the field. Wheat stem sawfly females will lay their eggs in the trap crop as long as they find the crop more attractive than the inside crop.

3. Is oat an effective crop to utilize as a trap crop? (Weaver) Yes, but only in certain varieties of spring wheat which produce less desirable odors. Oat varieties vary in their attractiveness to wheat stem sawfly. They cannot compete with the attractiveness of winter wheat, for example. Certain varieties are equal to or slightly more attractive than late planted spring wheat varieties like Corbin, Gunnison, Vida, O'Neal, Conan or Mott.

4. Why are we seeing low wheat stem sawfly infestations on the Highwood Bench? It was stated by David Weaver who spoke at the 2014 wheat stem saw-fly conference in Bozeman. Weaver stated that he is finding dead larvae in wheat stems grown in higher rainfall areas. We are uncertain if the increased mortality is because of increased plant resistance, or if it is because of a number of factors including plant resistance, increased beneficial organisms and increased crop rotation. Scott Meers (Alberta entomologist) stated that they have not recently seen damaging populations of wheat stem sawfly in Alberta. Meers blames low sawfly numbers in Alberta on increased crop rotations, and low acres of winter wheat seeded.

For further information on wheat stem sawfly management, please contact the Chouteau County Extension office at 622-3751, or stop by for a visit at the Chouteau County Courthouse. The Extension is located in the basement.

Montana State University, U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action

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