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Ontario Grain Farmer Magazine

Weed management issues in corn, soybean and wheat in Ontario

Principal Investigator

Peter Sikkema

Research Institution

University of Guelph

External Funding Partners

This project was funded in part through Growing Forward 2(GF2), a federal-provincial-territorial initiative. The Agricultural Adaptation Council assists in the delivery of GF2 in Ontario.

Project Start

May 2014

Project End

October 2017

Objectives

  • Determine if there is value to adding a fungicide to the last postemergence herbicide application in corn.
  • Determine the effect of Assure, Venture and Select on corn emergence and yield when they are applied to kill a poor stand of Roundup Ready corn and replant to corn.
  • Determine if dicamba (XtendiMax with VaporGrip) antagonizes the activity of Group 1 herbicides (Assure, and Select) for the control of volunteer corn in RR2 Xtend soybean (Roundup Ready, dicamba tolerant soybean).
  • Determine the tolerance of winter wheat to herbicide + fungicide + foliar fertilizer (manganese and/or sulfur) combinations.
  • Determine the effect of soil applied broadleaf herbicides in soybean and postemergence broadleaf herbicides in wheat on the emergence, growth and development of tillage radish.
  • Determine if cover crops can be successfully established in 250 bu/ac corn.

Impact

  • The validation of whether the addition of a fungicide to the last POST herbicide application in corn results in reduced disease incidence and increased yield will allow growers to be more efficient in pesticide use and application, maximizing their return on investment.
  • The validation of whether the addition of XtendiMax to Assure Select or in Roundup Ready Xtend soybean reduces the control of volunteer corn will allow growers to have more informed management decisions.
  • The validation of whether the addition of ammonium thiosulfate to herbicide/fungicide combinations in winter wheat increases crop injury or yield will allow growers to be more efficient in pesticide use and application, maximizing their return on investment.
  • The determination of whether broadleaf herbicides used in soybean or wheat negatively affects oilseed radish establishment will allow growers to be more confident integrating the oilseed radish cover crop into their current cropping system.

Scientific Summary

Disclaimer: The information presented here does not constitute a recommendation by the researcher or Grain Farmers of Ontario. Always read and follow the pesticide label before use. Always ensure that you have the most current label.

Weed control is the single most important aspect of pest management in corn. Seventy-one studies conducted in Ontario over a nine year period found a 102 bu/ac or 49% yield loss in corn where no weed management tactics were implemented. Every year there are new issues to address in respect to weed management in corn, soybean and wheat in Ontario. These issues arise as a result of a) changes in nutrient deficiencies due to changes in crop production systems, b) new herbicide resistance traits (e.g. Roundup Ready Xtend, Enlist), c) new tankmixes of herbicides plus fungicides plus micronutrients, and d) new crop production systems including cover crops. Ontario growers and crop consultants are demanding local data to determine the main reasons for the extreme variability in corn responses with the addition of a tankmix of fungicide plus glyphosate. With the recent registration of Roundup Ready Xtend soybean, local data is needed to determine if the addition of Xtendimax to Group 1 herbicides antagonizes volunteer corn control. Winter wheat producers are interested in minimizing the number of trips across the field with their sprayers, especially to reduce tramping; some growers have combined their herbicide, fungicide and foliar fertilizer with mixed results. One aspect of cover crops that needs further research is the effect of residual herbicides in soybean and wheat on the emergence and growth of oilseed radish.

This project aims to provide Ontario grain growers with additional information on how to manage their crops that result in excellent weed and disease control, minimal crop injury and allow for the successful establishment of cover crops. In corn there will be experiments conducted to determine on the effect of fungicide plus Roundup, and the tolerance of corn to Group 1 herbicides. Six field studies will be conducted to determine if the addition of XtendiMax (dicamba) in RR2 Xtend soybean antagonizes the control of volunteer corn with Assure or Select. Twelve field experiments will be conducted to determine the effect of herbicide (Buctril M, Refine M, Infinity or Estaprop), fungicide (Quilt, Stratego or Twinline) and/or ammonium thiosulfate applied alone or in combination on winter wheat. Twelve field experiments will be conducted to determine the effect of herbicides in soybean and wheat on cover crop establishment. Two field studies will be conducted to determine the establishment of annual ryegrass in corn.