Thursday, June 3, 2010
Control of Volunteer Soybean in Corn
This week I have received several inquires about the presence and potential impact of volunteer soybean in corn and cost-effective control procedures. The scenario of volunteer soybean in corn is a fairly recent phenomenon due to the wide-spread use of the glyphosate-resistant technology in corn and soybean. As a result, to my knowledge, data on corn yield loss potential as a function of volunteer soybean density is not available. However, I do know of one NDSU study conducted by Dr. Richard Zollinger that does evaluate several herbicide options to control volunteer soybean in corn. You can find a general summary titled Control of Volunteer Roundup Ready Crops at:
http://z.umn.edu/ndweedguide and click on Weed Control Ratings.
Overall, soybean size at time of herbicide application will determine the degree of control with small, V2 to V3 soybeans more effectively controlled than soybeans in the V4 to V6 growth stage. Application to small plants is especially important if you want to keep your herbicide application rates low.
Due to its low-cost, several growers have been interested in using 2,4-D to control volunteer soybean, however, based on Dr. Zollinger's work and personal experience, soybeans are not as sensitive to 2,4-D as they are to the other plant growth regulator herbicides - dicamba or clopyralid. Another low-cost alternative being discussed by producers is atrazine and would be a better option than 2,4-D due to it's crop safety and level of soybean control but is less effective as soybeans enter the V4 to V6 growth stage.
Plant growth regulator herbicides such as Hornet contain clopyralid and should provide effective control to smaller soybeans. Products that contain dicamba, such as Status, Distinct and numerous generics should provide effective control over a wider range of volunteer soybean crop sizes.