Drought continues to cause concern when it comes to herbicide carryover in western Canada.

On October 19, Corteva Agriscience released its list of products that are considered high risk for carryover, if certain amounts of precipitation have not fallen across the Prairies.

A combination of very hot, dry conditions have lead to increased evapotranspiration, which can dry soils quickly and reduce microbial activity, says the company. Under those unique conditions, the minimum recorded rainfall may not be adequate to consistently increase microbial activity, especially with reduced crop stands.

Corteva is making the following recommendations based on Environment Canada precipitation maps covering the Prairies.

The company also states that Environment Canada and provincial rainfall data are only to be used as a guideline, as rainfall can vary greatly within a small radius, adding that “personal or local rainfall records should be used to add to the data.”

 

Clopyralid  products

  • Lontrel, Cirpreme, Eclipse, Prestige, Spectrum, Prominex, and Salute
  • Corteva says the minimum rainfall required to adequately breakdown clopyralid is 140 mm (5.5 inches) from June to August in the year of application and 175 mm (6.9 inches) for the annual year in question.
  • For farmers within an area with less than 140 mm of rain in 2021, Corteva does not recommend seeding peas or soybeans in 2022 on fields treated in 2021 with the products listed above.

Clearfield canola herbicides

  • Ares SN contains two actives from the imidazolinone herbicide group, which can remain bound to clay and organic matter for longer periods of time in dry and cold soil conditions.
  • Corteva says at least 125 mm (5 inches) of rain from June 1 to August 31 are required in the year of application for adequate microbial breakdown of the active ingredients.
  • Oats and durum wheat are not recommended to be grown in rotation after Ares/Ares SN.
  • For fields where Ares or Ares SN were applied in 2020, where severe drought was experienced in 2020 and 2021, Corteva recommends that non-Clearfield canola, oats, or mustard should not be grown in 2022.

The company says that any further questions can be directed to a local Corteva territory manager.

 

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