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Volunteer corn generally has a minimal effect on corn yield potential, especially if management tools are employed. However, a study in Indiana indicated significant soybean yield loss starts to occur at 12 plants per 20 square feet (or 26,136 plants per acre).1 Research in South Dakota indicated soybean yield reductions of 50 to 60% at densities of 26 plants per 20 square feet (or 56,635 plants per acre).2 Remember to consider the distribution of volunteer corn when evaluating the potential yield loss. While 12 plants per 20 square feet may be realistic in a small area of the field, volunteer corn densities are less likely to be that high throughout the entire field.
In addition to the potential for yield loss, volunteer corn can also support corn rootworm activity. Volunteer corn left in soybean fields (Figure 1) can allow rootworm larvae to complete their life cycle which can result in higher rootworm populations for the next growing season. The potential increase in rootworm population may contribute to corn products not reaching their genetic yield potential in fields that rotate to corn the following year. Additionally, volunteer corn can attract adult female rootworm beetles that can lay eggs. Managing volunteer corn early in the season is the best method to reduce the potential for reduced yield from rootworm activity.
Glufosinate can be a tool to help manage glyphosate tolerant volunteer corn if the current corn crop contains LibertyLink® technology, such as with Genuity® SmartStax® Technology corn and that technology was not present in the preceding crop. When applicable, be sure that the refuge also is tolerant to glufosinate. Follow all label directions, as control can be variable depending on corn growth stage and environmental conditions.
Integrating management tools for prevention can help relieve the need for the rescue situations in crop. Using prevention and control tactics will likely provide the best results.
Sources: 1 Marquardt, P.T. and Johnson, W.G. 2008. Competition of glyphosate-resistant volunteer corn with glyphosate-resistant soybean. North Central Weed Science Society Proceedings 63:59. 2 Alms, J., Moechnig, M., Deneke, D. and Vos, D. 2007. Competitive ability of volunteer corn in corn and soybean. South Dakota State University. North Central Weed Science Society Proceedings 62:14. 3 Johnson, B., Jordan, T. and Nice, G. Methods to control volunteer Roundup-Ready or glyphosate-tolerant corn in a corn replant situation. Produced and prepared by Purdue University Extension Weed Science. Purdue University. www.btny.purdue.edu. Other sources: Davis, V.M. 2009. Volunteer corn can be more than an eyesore. The Bulletin. No. 21, Article 4. University of Illinois. Stahl, L.A.B., Haar, M.J., Getting, J.K., Miller, R.P. and Hoverstad, T.R. 2007. Effect of glyphosate-resistant volunteer corn on glyphosate-resistant corn. University of Minnesota. North Central Weed Science Society Proceedings 62:48. Web sources verified 6/2/15. 150601084954