Controlling Canada fleabane in soybeans
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:
For pre-emergent and residual activity against Canada fleabane in all soybeans:
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.
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”. https://fieldcropnews.com/2016/03/herbicide-resistant-weed-maps/#resistant