Cover Crops and Wheat Stem Maggot in Corn - Description and Control

Throughout the Corn Belt, growers often utilize cover crops as part of their corn management strategies. Depending on the grower’s goals, utilized cover crops can range from crops such as winter wheat and ryes to peas and clover as well as various mixtures. Improved corn yields following a cover crop can be realized from several benefits: soil erosion prevention, moisture conservation, reduced need for pesticides, reduced fertilizer costs and improved soil health.1

When considering cover crops, proper management of those cover crops in corn is key to help ensure growers can realize the potential benefits. Insect pests like wheat stem maggot (WSM) have been known to have an economical yield impact on corn; growers have reported losses of up to 30 bu/acre when the maggots are present and not managed properly.2

Wheat Stem Maggot

Wheat stem maggot is largely found in wheat growing regions across North America. The pest overwinters as a larva in the lower parts of the stems in cereals such as wheat and rye as well as other grass species.

The adult fly emerges in May from the larvae that pupate in the spring. The flies then lay their eggs on the stems of host plants. Upon hatching, the maggots feed inside the stems, causing the whitening (dead) wheat head. There are multiple generations throughout the season with the final generation in the fall where the emerging adults lay their eggs in the new winter wheat crop.3 When corn is planted into infested wheat or rye cover crops, emerging WSM adults can lay their eggs on the emerging corn, causing seedling damage.

WSM Management and Control in Corn

There is no simple solution for the control of WSM if cover crops are infected. Proper thresholds and recommendations of insecticides have not been established for control within wheat crops let alone corn planted into cereal cover crops. The best recommendation is early termination of the cover crop at least 14 days before planting corn.4 The benefits of cover crops as with any corn management consideration can only be realized through trial, monitoring and documentation.

Sources:

1Bowman, G., Cramer, C., Shirley, C., et al. (3nd edition). Managing cover crops profitably. Handbook Series Book 9. Sustainable Agriculture Research & Education (SARE). https://www.sare.org/.

2McMechan, J., Wright, R., and Inveninato Carmona, G. 2018. Wheat stem maggot in corn: Plan on scouting your cover crop fields this spring. CROPWATCH. University of Nebraska – Lincoln. https://cropwatch.unl.edu/.

3Sloderbeck, P.E., Michaud, J.P., and Whitworth, R.J. 2013. Wheat Insects. Department of Entomology. Kansas State University. https://entomology.k-state.edu/.

4McMechan, J., Wright, R., and Inveninato Carmona, G. 2018. Wheat stem maggot adult monitoring: A pest of cover crop-to-corn transitions. CROPWATCH. University of Nebraska – Lincoln. https://cropwatch.unl.edu/.

Web sources verified 1/13/2020

Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.

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Cathy Soanes

Channel Technical Agronomist

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