CORN Newsletter: 2009-14, May 18, 2009

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C.O.R.N Newsletter 2009-14
May 18, 2009 - May 26, 2009

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A few more things about 2,4-D ester
by Mark Loux


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Just when you thought it was safe to read C.O.R.N. without seeing us preach yet again about the importance of 2,4-D in burndown treatments, we have some final comments to make on this subject. We have had questions about the risk of injury to corn from 2,4-D applied early postemergence. Small, emerged corn is usually extremely tolerant of 2,4-D, and our perspective is that application of 2,4-D to corn that is spiking can be safer than preemergence applications. The primary concern with a preemergence application is that a heavy rain will occur before corn has emerged, moving the 2,4-D down toward the not yet emerged corn shoot. This occasionally results in crop injury, whereas small, emerged corn usually tolerates 2,4-D well.

We are not including this information to discourage preemergence applications of 2,4-D, especially this week when we have a string of dry days in the forecast. Our main point is to provide some reassurance that 2,4-D can be included in herbicide treatments even after corn has emerged. The rate of 2,4-D that can be applied is lower on emerged corn compared with preemergence applications, but most labels still allow up to 0.5 lbs ai/A on emerged corn. Some 2,4-D labels allow broadcast postemergence application anytime after corn has emerged, while others specify that corn should be 4 inches tall. Most labels contain a statement to the effect that 2,4-D should be applied as a directed spray using drop nozzles once corn has reached a size of 8 inches, because the risk of injury increases on larger corn.

Also, a final caution to nonGMO soybean producers about the decision to omit 2,4-D ester from burndown treatments. Doing so can greatly increase the risk of experiencing unsolvable weed control problems in this year’s soybeans (i.e. you may end up with a big mess on your hands). The postemergence herbicides that can be used in nonGMO soybeans are not likely to adequately control the weeds that survive an inadequate burndown. The widespread resistance to glyphosate and/or ALS inhibitors in marestail and ragweeds can make these weeds difficult to control without the use of 2,4-D. Large, aged lambsquarters can also be tough to control with glyphosate alone, or with postemergence herbicides that are not that good on lambsquarters to begin with. Our primary suggestion here, especially in fields with a history of herbicide resistance, is to go ahead and use 2,4-D ester in the burndown, even if it means further delays in soybean planting. The success of your nonGMO soybean crop may depend upon it.

Readers can subscribe electronically to this newsletter by signing up at http://agcrops.osu.edu/services/email.html. E-mail labarge.1@osu.edu if you have problems subscribing or no longer wish to receive this newsletter.

C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868


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