Canada Fleabane

Controlling Canada fleabane in soybeans

Canada fleabane close up 

Canada fleabane weed mature 

Canada fleabane weed in bloom

Canada fleabane first appeared in Ontario in 2010 and by February 2021, populations resistant to herbicide Groups 9 and 2 were identified throughout Ontario’s soybean growing regions. In one worrying development, biotypes resistant to Group 22 were found in Essex County.1

Canada fleabane seeds can germinate all year, but most do so from late summer to early fall, forming overwintering rosettes – like any winter annual. Spring-germinating seeds just skip over the dormancy period and grow to maturity like any other summer annual. And there’s the rub – Canada fleabane is constantly emerging. It produces fluffy flowers that, in the same manner as dandelions, disperse tiny, parachute-packing seeds over long distances in the wind.

This is one of the most tenacious and prolific weeds facing soybean growers and dealing with it requires an equal amount of tenacity and planning. There are three main things to consider when it comes to managing resistant and non-resistant Canada fleabane in soybeans:

  1. Early removal is essential. The critical weed-free period in soybeans is from the first to third trifoliate, which means pre-emergent herbicides and residual activity are a cornerstone when it comes to managing Canada fleabane.
  2. Follow a Program Approach with MMOA for best control. Since most Canada fleabane is herbicide resistant, ensure you use multiple modes-of-action (MMOA) for improved control and resistance management.  Make sure to include effective herbicides like metribuzin. 
  3. Consider a fall burndown. One Canada fleabane plant can product up to 200,000 seeds, so if weed pressure is high, think about a fall burndown to keep it in check. 

Corteva solutions

Corteva has a portfolio of herbicides with excellent activity against Canada fleabane in both glyphosate-tolerant and identity-preserved (IP) soybeans. 

For pre-emergent and residual activity against Canada fleabane in all soybeans:

  • Canopy PRO herbicide. A great start to a Program Approach in Enlist E3 soybeans, Canopy PRO delivers broad-spectrum residual control when applied pre-plant or pre-emergence, including no-till burndowns.
  • Commenza™ herbicide. An MMOA stalwart, and safe to use on IP soybeans, Commenza contains Group 2, 5 and 15 actives and can be applied either pre-plant or pre-emergence for early season weed control and broad-spectrum residual activity.
  • Elevore herbicide with Arylex active. This Group 4 pre-plant burndown herbicide offers effective control of Group 9 and Group 2 resistant Canada fleabane.

If you’re growing Enlist E3 soybeans, Corteva has two herbicides that control Canada fleabane. Both contain Colex-D technology for near-zero volatility and low drift.

  • Enlist Duo herbicide. This is a proprietary blend of 2,4-D choline (Group 4) and glyphosate (Group 9) can be applied at pre-plant, pre-emergence and post-emergence so you can time your application to the ideal weed or crop stage. When applied PRE, Enlist Duo can be tank mixed with Canopy PRO for residual weed control as your crop establishes.
  • Enlist 1 herbicide. Designed for in-crop use, Enlist 1 is a stand-alone 2,4-D choline formulation that can be applied up to full flower (R2) when tank mixed with glyphosate, or up to starting bloom (R1) when tank mixed with Liberty 200 SN (glufosinate). Enlist 1 herbicide can play a key role in your MMOA weed control strategy.

To sum up

Canada fleabane is very tough to control and requires a serious, season-long, rotation-wide plan. Early weed removal is absolutely key, but its prolific nature means that a second, in-crop herbicide pass is often necessary to keep Canada fleabane down. It has already developed known resistance to three herbicide groups, so pay attention to a MMOA strategy when it comes to herbicide choice. 

1Field Crop News. Herbicide Resistant Weed Maps. Results from interactive table “Weed species confirmed resistant to a herbicide group by county in Ontario since 1981”.