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Ontario Grain Farmer Magazine

Development of the building blocks for integrated weed management programs for control of glyphosate and multiple-resistant weeds

Principal Investigator: Peter Sikkema

Research Institution: University of Guelph (U of G)

Timeline: April 2019 – March 2024

Objectives:

  • To develop the building blocks for Integrated Weed Management (IWM) strategies for the control of glyphosate-resistant (GR) and multiple-herbicide-resistant (MHR) weeds in Ontario.
  • To improve the consistency of MHR Canada fleabane in corn, soybean and cereals.
  • To improve the consistency of MHR waterhemp in corn, soybean and cereals.
  • To improve the consistency of GR giant ragweed control in soybean and cereals.
  • To evaluate building blocks of an IWM program – such as new herbicides, crop row widths, crop rotations and cover crops as part of a diversified IWM strategy.

Impacts:

  • The potential financial loss to Ontario farmers resulting from MHR Canada fleabane competition in corn, soybean and cereals could reach $559 million annually if no weed management tactics were employed by Ontario farmers. Assuming that yield loss is reduced by 90% with current weed management strategies, Ontario farmers still incur a financial loss of $56 million annually. If yield loss due to MHR Canada fleabane were decreased to 5%, it would result in a benefit to Ontario farmers of $28 million annually.
  • The potential financial loss due to competition from uncontrolled GR giant ragweed in Ontario corn, soybean and cereals could be as high as $134 million annually. Assuming that current weed management strategies limit yield loss to 10%, Ontario farmers are still losing $13.4 million annually. If this research can decrease yield loss due to MR giant ragweed across Ontario to only 5%, the annual benefit to Ontario farmers would be $6.7 million.
  • Without weed management tactics, the financial loss attributable to MHR waterhemp competition in corn, soybean and cereals in Ontario could potentially reach $10 million annually. Assuming that with current weed management strategies, the yield loss is reduced by 90%, the annual loss to Ontario farmers is still $1.0 million. Through this research program, if yield loss due to MR waterhemp across Ontario were decreased to 5% it would result in a benefit to Ontario farmers of $0.5 million annually.
  • It is expected that the areas infested with MHR waterhemp in Ontario will increase rapidly. From studies conducted on Ontario farms, in the most competitive environments waterhemp interference in corn and soybean resulted in yield losses of 84 and 93%, respectively. In corn, assuming an average yield of 159 bu/ac and selling price of $4.87 (OMAFRA 2016) this represents a potential loss $648/ac due to waterhemp interference. In soybean, this translates to a loss of $546/ac due to waterhemp interference, assuming an average yield of 46 bu/ac and selling price of $12.78 (OMAFRA 2016). On a provincial basis, the potential monetary loss to Ontario farmers is millions of dollars if growers do not implement effective MHR waterhemp control strategies. It is anticipated that the results of this research will substantially reduce the financial loss to Ontario farmers due to MR waterhemp. 
  • This research program will help Ontario corn, soybean and cereal producers determine exactly which herbicide(s)/herbicide tank mixes to use to address MHR weeds on their farm and how to incorporate this information into a diversified IWM program.

Scientific Summary:

Glyphosate resistant (GR) weeds are present on 35% of Ontario farms (Stratus survey). GR Canada fleabane, giant ragweed, waterhemp and common ragweed have been confirmed in numerous counties in Ontario. The number of acres infested continues to increase. Based on studies completed on Ontario farms, GR Canada fleabane, giant ragweed, waterhemp and common ragweed interference reduced corn yield on average of 64, 72, 23 and 75% while in soybean the average yield loss was 70, 73, 43 and 75% respectively.

In 2018, the challenge of GR and MHR weeds has been exacerbated with the confirmation of four-way MR waterhemp (Groups 2, 5, 9 and 14) on at least 17 farms in Essex and Lambton counties. This is the first weed biotype with four-way herbicide resistance documented in Ontario. It is expected that this MHR biotype will be found at more sites over time which will dramatically increase the challenge for Ontario farmers. The rapidly changing and widespread presence of GR and now MHR weed biotypes necessitates continued research on development of new weed management solutions for Ontario farmers. Research from only a few years ago may no longer be relevant.

Control of MHR Canada fleabane is variable across Ontario and the USA. Continued research is required to improve the consistency of control, especially in soybean to minimize yield and financial losses for farmers. This project will include studies of both fall and spring herbicide applications as well as examining the impact of crop rotation and cover crops.

New strategies need to be developed for the control of MHR waterhemp to improve control, reduce yield and financial losses and slow its migration across the province. Ultimately, the goal of MHR waterhemp weed control programs may have to be zero weed seed return to the soil to stop its spread across Ontario. This project will evaluate several new herbicides, including, but not limited to Bayer-478, tolpyralate, trifludimoxazin and V-10456 (and others as they are released for public testing) for the control of MHR waterhemp in the province. It is important that these new herbicides be evaluated under Ontario conditions and at use rates registered in Canada, to continue to move the science of weed management forward. These new herbicides need to be compared to the current industry standards to determine if control can be improved and/or costs can be reduced for growers. Studies will be completed in corn, soybean and cereals.

The overall goal of this research is to develop the building blocks for integrated weed management (IWM) programs based on sound science. The identification of effective building blocks will allow Ontario farmers to implement unique IWM programs tailored to their unique farming operation.

External Funding Partners:

BASF

Bayer

Corteva

FMC

Syngenta

Valent / Nufarm