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Dicamba Stewardship

06/04/2021

Dicamba Stewardship

By Connor Charlton, B.Sc.Agr
Crop Sales Specialist
AGRIS Co-operative - Chatham

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Connor received a Bachelor of Science degree in Agriculture (crop, horticulture and turf grass sciences) from the University of Guelph. He plans to get his CCA (Certified Crop Advisor) designation this coming winter.

Connor is from the Merlin area, where his family has a cash crop farm growing I.P. soybeans, wheat and corn.

Read more about Connor.


As we enter into June, warm weather, inversion risk, and sensitive crops emerging call for a review of dicamba stewardship.

Roundup Ready 2 Xtend® soybeans make up a significant share of the soybeans grown in Ontario. They offer the ability to apply Group 4 dicamba products such as Xtendimax® and Engenia®. There have been concerns & hesitation in recent years due to off-target movement, however it is important to remember that these are still very effective and safe products when used properly.

This May brought us a heat wave that allowed most growers to get their crops in the ground. This heat wave brought along conditions that created a potential for inversion events and high volatility, making dicamba applied in these conditions susceptible to off-target movement.

What is an inversion?

On a normal day, the warmest air is located at the soil surface. This warm air rises into the cooler atmospheric air, allowing for an upward movement of air and the particles (such as dicamba) within it.

During a temperature inversion, a cold layer of air becomes trapped at the soil surface below a warm layer, preventing the upward movement of air and particles (such as dicamba). Since the air cannot move upwards, it moves laterally which can result in off-target movement.

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Signs of a temperature inversion

  • Fog/haze hanging in the air
  • Rapid temperature changes, typically in the morning & evening
  • Low wind speeds which prevent air from mixing

Best practices for dicamba use

  • Only apply between 1 hour after sunrise to 1 hour before sunset.
  • Evaluate area for sensitive crops
  • Ensure that temperatures are between 10 to 28 degrees Celsius
  • Do not spray in dead calm, ensure winds are between 3-15 km/h
  • Do not spray at speeds greater than 25 km/h
  • Minimum 10 GPA water volume
  • Use nozzles that create extremely coarse or ultra-coarse droplets

Tools available to growers

Engenia Spray Tool:

Provides a 3-day forecast of hourly local conditions and the likelihood of an inversion.
Link: https://www.engeniaspraytool.ca/

RRXtend Spray App:

Mobile app which gives local weather data and inversion potential.
Link: https://www.roundupreadyxtend.com/stewardship/spray-app/Pages/Roundup-Ready-Xtend-Spray-App.aspx

New Seed Technologies:

  • XtendFlex® Soybeans offer the same herbicide options as Roundup Ready 2 Xtend soybeans, with the additional option of applying glufosinate (Liberty®). This provides an effective option to control glyphosate resistant weeds during periods that dicamba products cannot be safely used.
  • Enlist E3® Soybeans are tolerant to glyphosate, Enlist One® (2,4-D Choline), and glufosinate (Liberty). 2,4-D Choline is a low-volatility group 4 herbicide which offers a flexible window of application.

Using correct practices when spraying dicamba is extremely important. Do not hesitate to call your local AGRIS Co-operative Crop Sales Specialist with any questions.

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