Thursday, July 04, 2013
feature-horseweed-california-02222013

Illinois Soybeans: Controlling Large Horseweed and Waterhemp

AgFax.Com - Your Online Ag News Source


The volume of inquiries about how to control large (taller than 12 inches) horseweed (a.k.a. marestail) and waterhemp in soybean has remained consistent over the past 10 days.  The answer can be summarized as follows: there are NO postemergence herbicides that will consistently control these very large weeds in soybean, especially if these weeds are resistant to glyphosate.




Glyphosate-resistant waterhemp can be controlled by foliar-applied PPO inhibitors (such as lactofen (Cobra), fomesafen (Flexstar) or acifluorfen (Ultra Blazer)) in conventional or glyphosate-resistant soybean varieties, or by glufosinate (Liberty) in glufosinate-resistant (Liberty Link) soybean varieties.

However, it is very important to remember that these herbicides do not extensively translocate within the weed following their absorption through the leaf surface, and control of large weeds is often not as consistent as control of small (5 inches or less) weeds.  Reducing application rates of these herbicides often results in reduced waterhemp control.

In our research, we have observed less control of glyphosate-resistant waterhemp with tankmixes of glyphosate and fluthiacet (Cadet) or 2,4-DB compared with tankmixes of other PPO-inhibiting herbicides.  Keep in mind that PPO-resistant waterhemp biotypes are very common, and these biotypes are sometimes also resistant to glyphosate.

The only effective methods to control waterhemp plants resistant to PPO inhibitors and glyphosate include physically (i.e., weed hook or hoe) or mechanically (i.e. cultivate) removing the plants from the field.

The following text, written by Dr. Mark Loux, extension weed scientist at the Ohio State University, provides excellent information about managing marestail in double-crop soybean.

A weed free start is the most critical aspect of a weed management program for double-crop soybeans.  This can be challenging to achieve where glyphosate-resistant marestail are present after wheat harvest.

Problems with marestail include the following: 

  1. Most populations are now glyphosate-resistant and many of these are also ALS-resistant (we suspect ALS-resistant marestail exists in Illinois);
  2. It’s usually not possible to use 2,4-D ester and wait 7 days until double-crop soybean planting; and
  3. Marestail that were tall enough to be cut off by harvesting equipment will be even more difficult to control.

Our research indicates that there are no herbicide treatments that consistently control glyphosate-resistant marestail populations that have regrown following mechanical disturbance or prior herbicide treatment.  Certainly one of the best options is to plant LibertyLink soybeans, which allows for a POST application of Liberty to help control plants that survive a preplant burndown.

The following are the most effective burndown options for control of marestail prior to double-crop soybean emergence:

  • Liberty (32 to 36 oz) + Sharpen (1 oz) + MSO + AMS (can also add metribuzin)
  • Liberty (32 to 36 oz) + metribuzin (4 to 8 oz of 75DF) + AMS
  • Glyphosate (1.5 lb ae/A) + Sharpen (1 oz) + MSO + AMS

We suggest using a spray volume of 20 gpa for any of these treatments, and avoiding nozzles that produce large droplets.  Results with a combination of glyphosate and 2,4-D may be more variable then the treatments listed.

With regard to the control of weeds that can emerge after double-crop soybean planting, and the entire weed control system, the following approaches can be considered.

1.  Plant any type of soybean, and include a residual herbicide with the burndown treatment so that POST herbicides are not needed.  A good strategy in Roundup Ready or nonGMO soybeans even where POST treatment is needed, since POST marestail control might be impossible in these systems.  Residual herbicides used at this time of the year should be restricted to those that have little or no carryover risk – such as metribuzin, Valor, or low rates of chlorimuron or cloransulam products.

2.  Plant a LibertyLink soybean, and apply Liberty POST as needed.  Probably the best option for control of later-emerging marestail or plants that regrow after the burndown, assuming that there is any Liberty available.

3.  Plant a Roundup Ready soybean and apply glyphosate POST.  Should work for most weeds, but not a good choice if the POST application needs to control marestail.

4.  Plant a nonGMO soybean and apply conventional POST herbicides (Flexstar, Fusion, Select, etc) as needed.  This system has the most potential for soybean injury, but seed may be cheaper than the other systems.  Not a good choice if the POST application needs to control marestail.


Tags: , , , , , , ,


Leave a Reply

Name and Email Address are required fields. Your email will not be published or shared with third parties.

Sunbelt Ag News

    Peanut Harvest: More Digging In SE; Western Growers Gearing Up – AgFax9-20

    Southern Soybeans – Tough, Late-Season Insect Decisions – AgFax9-20

    Rose on Cotton: Bears in the Woods; World Production Could Climb9-19

    Nebraska: Multiple Herbicide-Resistant Weeds and Challenges Ahead9-19

    Cotton Harvest – Midsouth – Picking, Cotton Defoliation Gear Up – AgFax9-19

    Cleveland on Cotton: Market is Dog Paddling; China Offers a Bone9-19

    Texas Rice: Weevil Loves to Eat Hemp Sesbania9-19

    U.S. Rice Growers Have a Market Opportunity in North Africa9-19

    DTN Livestock Close: Futures Higher on Late-Week Short Covering9-19

    Juggling the Soybean Harvest: Making the Best Decisions on When to Start – DTN9-19

    Rice Crop: Texas, Louisiana Harvests Wrap Up, Rains Slow Progress in Delta9-19

    Rice Market: Short Side Dangerous, Long a Test of Patience9-19

    Doane Cotton Close: Bearish Chinese Sentiments Weigh on Futures9-19

    AFB Grain-Soybean Close: Sell Off Continues9-19

    AFB Cotton Close: Dec. Violate Trendline Support9-19

    AFB Rice Close: Ends Week on Positive Note9-19

    Welch on Wheat: 74% of Spring Crop Harvested9-19

    DTN Cotton Close: Gives Back Last Week’s Gains9-19

    Welch on Grain: No Change to Corn Condition Ratings9-19

    DTN Grain Close: New Lows for the Markets9-19

    USDA: Peanut Price Highlights9-19

    DTN Livestock Midday: October Hog Futures Skyrocket Higher9-19

    DTN Grain Midday: Lower as Selling Pressure Continues9-19

    Cotton Harvest – Southeast – Pickers Running – AgFax9-19

    DTN Dried Distillers Grain: Prices Moving Downward Again9-19

    DTN Crop Tech: NASA to Launch Soil-Moisture Satellite9-19

    DTN Cotton Open: Falls in Brisk Early Dealings9-19

    California Cotton Defoliation – Gearing Up Early – AgFax9-19

    DTN Livestock Open: Lean Hog Futures Set for Bullish Start9-19

    DTN Grain Open: Futures Off to Lower Start9-19

    Georgia Soybeans: Kudzu Bug Numbers Much Lower This Season9-19

    Keith Good: Soybean Futures Hit 4-Year Low; Wheat, Corn Tumble, Too9-19

    Most Farmers Willing to Take More Steps to Improve Water Quality, Says Study9-18

    Corn: Nutrient Balance More Important Than Increasing Nitrogen9-18

    Arkansas Woman Joins Husband with 2nd Consecutive 100 BPA Soybeans9-18

    Chumrau on Wheat: Huge Corn, Soy Harvests Will Test Grain Supply Chain9-18

    Keeping Your Cover Crops Legal — DTN9-18

    U.S. Grain Transportation: Miss. River at St. Louis Unusually High9-18

    Corn: Be Wary of Potential Storage Issues — DTN9-18

    Wheat: Producers Urged to Keep Eye on Black Sea Countries’ Markets9-18

    Updating ARC-CO and PLC Payment Indicator for 2014 Crop Year9-18

    U.S. Drought Outlook: Improvements in Texas, Southwest9-18

    Harvest Approaches in Iowa; Time for More Planting in Florida — DTN9-18

    U.S. Energy: Shale-Focused Companies’ Financial Performance Improves9-18

    Gasoline Prices: Average Falls 5 Cents9-18

    Propane Stocks: Rise by 1.4M Barrels9-18

    Diesel Prices: Decrease by a Penny9-18

    Soybeans, Corn in Midwest: Heavy Rain, Early Frost, Slow Going – AgFax9-17

    Farmers First Line of Defense in Keeping GMOs Out of Export Shipments – DTN9-17

    Ohio: 7 Counties Declared Natural Disaster Areas9-17

    California: 42 Counties Designated Natural Disaster Areas9-17

    Hearing Reflects Highly Politicized Debate Over Biotech Crops — DTN9-17

    DTN Fertilizer Trends: Rabobank Forecasts Higher 3Q Retail Prices9-17

    Cotton in Southwest: Need More Heat; 4-Bale Dryland; Pigweed Plans – AgFax9-17

    China Agrees to Buy $2.3B Worth of U.S. Soybeans — DTN9-17

    Somebody’s Got Gas – Pig Manure for Natural Gas Production – DTN9-16

    Non-Land Production Costs Unlikely to See Much Decline in 20159-16

    USDA: Weekly National Peanut Prices9-16

    Georgia Soybeans: Grower Randy Dowdy Breaks The 100-Bushel Barrier9-16

    Insure Your Crop Revenue Guarantee — DTN9-16

    Sunbelt Ag Events

     

    About Us

    AgFax.Com covers agricultural trends and production topics, with an emphasis on news about cotton, rice, peanuts, corn, soybeans, wheat and tree crops, including almonds, pecans, walnuts and pistachios.

      

    This site also serves as the on-line presence of electronic crop and pest reports published by AgFax Media LLC (formerly Looking South Communications).

        

    Click here to subscribe to our free reports.

      

    We provide early warnings and confirmations about pests, diseases and other factors that influence yield. Our goal is to quickly provide farmers and crop advisors with information needed to make better and more profitable decisions.

         

    Our free weekly crop and pest advisories include:

    • AgFax Midsouth Cotton, covering cotton production and news in Alabama, Arkansas, Louisiana, Mississippi, Tennessee and Missouri.

    • AgFax Southeast Cotton, covering cotton production and news in Alabama, Florida, Georgia, North Carolina, South Carolina and Virginia.

    • AgFax Southwest Cotton (new for 2013!), covering cotton production and news in Texas, Oklahoma, Kansas and New Mexico.

    • AgFax West (formerly MiteFax: SJV Cotton), covering California cotton, alfalfa, tomatoes and other non-permanent crops in California's Central Valley.

    • AgFax Rice covering rice production and news in Arkansas, Louisiana, Mississippi, Missouri and Texas.

    • AgFax Peanuts, covering peanut production in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas and Virginia.

    • AgFax Southern Grain: covering soybeans, corn, milo and small grains in Southern states.

    • AgFax Almonds, covering almonds, pistachios, walnuts and other tree crops in California's Central Valley.

    • AgCom 101, providing guidance to ag professionals involved in social media.

    Our newsletters are sponsored by the following companies: FMC Corporation Chemtura Dow AgroSciences.

          

    Mission statement:

    Make it as easy as possible for our community of readers to find and/or receive needed information.

              

    Contact Information:

    AgFax Media. LLC

    142 Westlake Drive Brandon, MS 39047

    601-992-9488 Office 601-992-3503 Fax

    Owen Taylor Debra L. Ferguson Laurie Courtney

          

    Circulation Questions?

    Contact Laurie Courtney