At last summer's University of Illinois agronomy day, Patrick Tranel offered a half dozen weed management predictions that could keep no-tillers awake at night in the future. As reported by Tom Doran in Illinois AgriNews, Tranel says the weed challenges you’ll be facing 5 years from now will be totally different than today.
1 There is more weed resistance in pre-emerge herbicides than is realized. There are five weeds with resistance to chloroacetamide (Group 15) herbicides. While high concentrations of pre-emerge herbicides are applied with the hope residual control will extend at least 4 weeks, resistance concerns may reduce pre-emerge control to only 2-3 weeks. This will place added pressure on post-emergence strategies.
2 There’s more non-target site (metabolic) weed resistance than you realize. This resistance is much more difficult to manage since it often leads to unpredictable cross resistance among herbicide groups.
Plants accumulating enzymes that metabolize the herbicide at a faster rate will cause serious non-predictable cross-resistance concerns.
3 Resistance to group 4 herbicides (auxinics) will explode. Tranel says increased use of the new dicamba and 2,4-D tolerant technologies (coming with Enlist herbicide and Xtend soybeans) will increase the intensity of selection for resistance. He says 32 weeds already show some resistance to 2,4-D and dicamba.
4 Control of glyphosate-resistant grass weeds will become a major concern. While only five grass weeds are currently resistant to glyphosate, the new dicamba and 2,4-D compounds only work on broadleaf weeds. However, when you tankmix these broadleaf herbicides with glyphosate, the…