I’m seeing what I assume is glyphosate-resistant Canada fleabane all over the place. What is the best strategy to get rid of this weed in a corn, soybean and cereal rotation?

CORN: Control of glyphosate-resistant Canada fleabane has been most consistent with post-emergence herbicide applications, but good control can be achieved with pre-emergence herbicides. Of the pre-emergence herbicides, Integrity, Marksman, Callisto + Aatrex 480, Battalion and Banvel II are all good options. Post-emergence applications of Marksman, Banvel II, Pardner + Aatrex 480 and Distinct are also effective on glyphosate-resistant Canada fleabane. Aggressive primary tillage prior to planting to small fleabane rosettes can also be very effective.

ADVERTISEMENT

SOYBEAN: Glyphosate-resistant Canada fleabane is most difficult to control in soybean because few options exist to control it once the soybean crop has emerged. Therefore it must be controlled prior to planting. When research trials were initially done, the pre-plant tank mix of glyphosate + Eragon + Merge was the most effective option. However, as that treatment was evaluated over several seasons and locations, about one-third of the time, glyphosate + Eragon + Merge failed to provide commercially acceptable control of glyphosate-resistant Canada fleabane. To address this inconsistency, different tank-mix options were evaluated and, during the course of two seasons, the addition of Sencor 75 DF (metribuzin) at 538 g/ha. (215 g/acre) to glyphosate + Eragon + Merge improved control of glyphosate-resistant Canada fleabane. The equivalent rate of metribuzin in Sencor 75 DF can also be found in herbicides like Conquest LQ and Canopy Pro.

CEREALS: Infinity is the most effective at controlling Canada fleabane in winter wheat, spring wheat and spring barley. Lontrel 360 is also an effective option if growing spring wheat and barley.

POST CEREAL HARVEST: Once the cereal crop is harvested, a greater amount of sunlight will hit the soil surface and will either stimulate new weed germination or growth of Canada fleabane that was suppressed by the cereal canopy. To minimize Canada fleabane seed being produced and returned to the soil, an aggressive cover crop (e.g. oats, rye, clover, oilseed radish) should be planted. Alternatively, fall tillage should be done no later than four to six weeks after harvest or before weed seed reaches maturity.

Have a question you want answered? Hashtag #PestPatrol to @cowbrough or email Mike at [email protected].