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Bartels: Pre-emergence herbicides complement Roundup Ready beans
Ohio Farm News
By Steve Bartels

Have you noticed how Ohio State University Extension, Purdue University Extension, and University of Illinois Extension have been working together to bring more cost efficient and broader based research to the citizens of the three states? One of the latest examples can be found in the April 18 edition of the Crop Observation and Recommendation Network (C.O.R.N.) Newsletter.

Several publications are mentioned which are combined efforts of specialist from more than one of these prestigious universities.

Biology and Management of Horseweed has recently been updated and is the result of efforts from all three universities. Giant ragweed is commonly called horseweed by many of us, but when a weed scientist says horseweed, they are referring to marestail.

The 2006 version of the Weed Control Guide was a gigantic collaboration of Ohio State and Purdue to produce a 189-page bulletin on how to control weeds in the major field crops produced in the two states. A very concise two-page fact sheet, The Benefits of Pre-emergence Herbicides in Roundup Ready Soybeans, published by Bill Johnson and Glenn Nice, Purdue Extension Weed Science and Mark Loux and Jeff Stachler, Ohio State University Horticulture and Crop Science, makes a strong case for the benefits of using a pre-emergence herbicide along with your glyphosate product.

When do weeds start to reduce your yield? The authors of this fact sheet show that if your weeds emerge with the soybeans, waiting to apply the glyphosate until the weeds are 9 to 12 inches tall will cost you as much as 10 percent of your potential yield because of competition prior to control. To maximize soybean yield, you should apply your post emerge glyphosate when the weeds are no more than 6 inches tall.

Pre-herbicides reduce the early season weed pressure and they widen the post application window. They also improve control of some of the tough to control weeds such as lambsquater and waterhemp. The fact sheet says the use of pre-herbicides can increase yield by as much as 9 bushels per acre as compared to post glyphosate alone.

You can go to www.agcrops.osu. edu/weeds and click on the title of any of these publications for more information or, you can request it from your local extension office. If you have not yet signed up to receive the CORN newsletter, a weekly update on what is happening across the state and recommendations for control during the growing season, subscribe electronically by sending an e-mail message to:

This farm news was published in the May 3, 2006 issue of Farm World.