Strategies to stay ahead of glyphosate resistance

Published on: 14:35PM Jun 11, 2010
Chuck Foresman
Overall, Midwest planting this spring went much more smoothly than last year. But as glyphosate resistance spreads, growers and retailers rely on spring strategies to keep resistant weeds from causing problems in their corn and soybean fields. We had quite a few people visit this spring to build weed management solutions, which I hope you were able to implement.
In southern Illinois, retailers and growers acknowledge that glyphosate doesn’t control everything. Giant ragweed, waterhemp and marestail are confirmed resistant to glyphosate, and Palmer pigweed also appears to be resistant. So glyphosate-glyphosate-glyphosate programs raise a red flag.
According to a colleague in that area, retailers recommend controlling weeds before they emerge to stay ahead of resistance. Pre-emergence programs make a difference. 
And crop rotation does, too. One retailer encouraged a grower to plant a problem field to corn for a year to provide a broader range of pre-emergence options to manage resistance.
Further east, one colleague in Ohio talked with a couple growers about how weed resistance can explode unexpectedly. They had a little horseweed (marestail) show up in 2007 and 2008, but it wasn’t a big issue. As they prepared for planting in 2009, they weren’t concerned. But with a very wet, late spring, the weed grew quickly. By the time they got in the field, they weren’t able to control it – they learned it was resistant to multiple types of herbicide. This year they made a point to manage marestail with their weed control program, and they choose herbicides that have multiple modes of action.
Another Ohio retailer recommends herbicides with multiple modes of action to prevent glyphosate weed resistance from building in area fields.
So did weed resistance cross your mind when you were planting? What did you do to stay ahead of it?