Database Research Summaries2018 Tillage and other strategies for plyphosate-resistant waterhemp management
The focus of this project is to develop and strengthen our current recommendations for control of herbicide-resistant waterhemp.
- Evaluate the effect of deep tillage on waterhemp populations the following season.
- Evaluate the effectiveness of several Liberty (glufosinate)-based weed control programs on the management of herbicide-resistant waterhemp in Liberty Link soybean.
- Develop and evaluate various herbicide programs using dicamba (XtendiMax) in Roundup Ready 2 Xtend soybean for management of glyphosate-resistant waterhemp.
- Provide this new information on the management of herbicide-resistant waterhemp to Michigan soybean growers.
- The initial soil seedbank of waterhemp from greenhouse grow outs from fall collected samples was 20 plants per 4-inch diameter core at the 0 to 2-inch depth and 52 plants at the 2 to 7-inch depth.
- Waterhemp emergence in moldboard plowed peaked on June 14, averaging 28 plants per 0.25 m2. Soil-finished and no-till plots peaked one week later on June 21, averaging 19 plants, and 12 plants per 0.25 m2 respectively.
- Postemergence follow up applications of XtendiMax (dicamba) and XtendiMax + Warrant (acetochlor) provided excellent control of waterhemp when applied in July.
- At the time of the POST Liberty application, 40 DAP, all treatments provided 90% or greater waterhemp control with the exception of: Valor (2 oz), Metribuzin (8 oz), Valor + Metribuzin, and Warrant.
- After the POST Liberty application all treatments provided greater than 90% waterhemp control.
- Soil-applied applications of Valor at 2 oz/A provided 76-85% control of waterhemp until 40 d after planting (DAP) when the POST herbicide applications were made.
- Soybean injury from POST applications only occurred when the active ingredient fomesafen (Flexstar or Warrant Ultra) or lactofen (Cobra) was applied. Injury ranged from 14-23%, 7 d after treatment (DAT).
- Waterhemp control 30 DAT was greater than 90% with Liberty and XtendiMax treatments, with the exception of Liberty alone. Waterhemp control was between 80 to 88% when Flexstar or Cobra was applied.
- This research provides effective information to soybean growers to help manage this troublesome economically significant weed problem.
- This research provides additional control strategies and herbicide options to aid in the management of a weed that has the ability to develop resistance to multiple-herbicide sites of action.
For more information about this research project, please visit the National Soybean Checkoff Research Database.
Funded in part by the soybean checkoff.