Carrot herbicides

Tuesday, May 24, 2022


Warm, sunny days are upon us and planting is in full swing, but a recent re-evaluation of linuron by Health Canada has been cause for concern as things ramp up, especially for carrot growers. While some uses of linuron have been cancelled, continued use has been approved for carrots, parsnips, potatoes, asparagus, and shelterbelts. Unfortunately, the re-evaluation interrupted production schedules, resulting in shortages of a popular Group 7 herbicide that many growers rely on for weed control.  

In response to this situation, the Pest Management Regulatory Agency (PMRA) has approved an Emergency Use Registration (EUR) for Tough 600 EC herbicide in carrots, valid in several Canadian provinces, including Nova Scotia. Additionally, Ultra Blazer herbicide has received a User Requested Minor Use Label Expansion (URMULE) for use in carrots.

Ultra Blazer herbicide (acifluorfen) is a Group 14 herbicide approved for use in carrots to suppress redroot pigweed. This post-emergence herbicide works mainly by contact action and rainfall within 6 hours of application will reduce effectiveness. Cool weather or drought will delay herbicide activity. Contamination of groundwater may occur if this chemical is used in areas where soils are permeable (ex. sandy soil) and/or if the water table is shallow.

Tough 600 EC herbicide (pyridate) is a Group 6 herbicide approved for use in carrots between May 1, 2022 to December 31, 2022. This post-emergence herbicide is already approved for weed management in a variety of crops across Canada and carrots have shown tolerance in development trials. Not all carrot varieties have been tested, so it is recommended to test in a small area of the field first.


Tough 600 EC herbicide

Ultra Blazer herbicide

Active ingredient



Registration period

May 1-Dec 31 2022





Weed control

Post-emergent control of broadleaf weeds - redroot pigweed, common lamb’s quarters, false cleavers, black nightshade

Post-emergent suppression of redroot pigweed

Application rate

0.5 - 0.75 L/ha (use high rate when weed pressure is high or for harder to control weeds)

94 mL/ha with 0.5% v/v Assist Oil Concentrate

Applications per season



Application Timing

Apply to carrots in the 2 to 7 leaf stage that have sufficiently hardened off and have a waxy cuticle; apply to young, actively growing weeds

Apply after carrots have emerged and pigweed is in the 2 to 4 leaf stage


12 hr

12 hr


60 days

40 days


Do not apply either product to crops under stress.

Additional notes regarding use of Tough 600 EC herbicide:

Do not apply when the temperature is greater than 25oC (may cause crop injury). Application of this product is not recommended when temperatures will fluctuate more than 10oC in a 24-hour period, due to increased risk of crop injury.

Avoid irrigating for three days prior to herbicide application.

Delay application for three days after rain, cool, or cloudy weather to allow the crop to harden off.

Treated carrots may show signs of stunting, chlorosis, and/or partial defoliation of leaves present at the time of application, but the carrots typically outgrow these symptoms, with no adverse effects on crop vigour, maturity, or yield.

Tough 600 EC Herbicide offers contact control of susceptible species and has no residual activity. Crops rotated following the use of Tough 600 EC Herbicide should not be negatively impacted                                                                

For more information on these products, consult the label (see links below) or contact your local crop specialist or a representative from the chemical supplier.

Ultra Blazer herbicide - Label

Tough 600 EC herbicide - Label

Pesticide Label Search - Health Canada (