By Top Crop Manager
October 16, 2014 - OMAFRA's Mike Cowbrough, weed management field crops program lead, discusses what can be done to combat fleabane, which is popping up with glyphosate resistance in several Ontario counties.
If you traveled in southern Ontario this growing season it has not been hard to spot significant patches of Canada fleabane in soybean fields. Unfortunately there are 12 counties in Ontario with populations of this weed that are resistant to glyphosate.
To make matters worse the seed is highly mobile with a dispersal pattern similar to dandelion. How are we going to manage this? Below is a game plan wheat, soybean and corn based on the most recent Ontario research.
Quick biology facts
Recent research by Eric Tozzi and Rene Van Acker at the University of Guelph have shown that the majority of Canada fleabane plants germinate from mid August to mid November while a second germination window occurs from mid-May to mid-June. Fall emerging plants will rosette before overwintering, whereas spring germinated plants typically by-pass the formation of a rosette and go straight to bolting. Spring germinated plants will flower earlier than fall germinated plants. Seed can germinate in soils as low as 8 degrees Celsius but prefers soil temperatures at 14-15 degrees Celsius.
Control fall germinated rosettes either pre-plant or pre- wheat emergence with Eragon + Merge (glyphosate can be tank-mixed when applied pre-plant). In the spring, if fleabane rosettes have overwintered or spring seedlings have germinated then post -emergent applications of either 2,4-D Ester, Infinity or dichlorprop/2,4-D have all provided good control of Canada fleabane.Soybeans: Pre-plant control of this weed is critical since there is only one post-emergent herbicide option (FirstRate) and its control can be variable. The addition of either Eragon + Merge, Integrity + Merge, Amitrol 240, Broadstrike RC or 2,4D Ester to glyphosate has provided good control of Canada fleabane.Corn: Banvel II, Marksman and Distinct have been the most consistent herbicides at controlling heavy populations. Pardner + Aatrex 480, Peak Plus and Callisto + Aatrex 480 can provide control/suppression but have been less consistent. Most primary tillage operations ahead of planting corn will do a good job of eliminate seedling plants.
The use of cover crops, especially after wheat harvest will significantly reduce seed production of emerged plants and inhibit new seeds from germinating.