Many of you may have already read the Farm Journal/AGWEB article titled “Breaking Pandora’s Box: Resistant Weed Future Looms Large for US Farmers” by Chris Bennett. This article is a must read for Midsouth soybean producers.
The gist of the article is a prediction of future weed management in the face of rapidly developing weed resistance to current herbicides. Five eminent weed scientists offer their assessment of what the future may be like in the constant battle to control weeds that plague soybean fields. The following is a summary of each scientist’s assessment of where we are now and where we might end up.
Dr. Tom Barber, Univ. of Arkansas
• Glyphosate resistance in weeds is now omnipresent, and long in the rearview mirror.
• Resistant Palmer amaranth or pigweed is the bellwether weed in Arkansas soybean fields.
• Dicamba failure to control prickly sida or teaweed in soybean fields is a major concern.
• Most successful herbicide programs for pigweed include two to three applications of residual herbicides before and during the growing season.
• There’s a day coming when dicamba, 2,4-D, and glufosinate will no longer control pigweed on a large acreage.
• Weed control success starts with two residual herbicides at planting–a Group 15 herbicide and Group 5 metribuzin (two modes of action)–and continues with a timely POST application when weather allows.
Dr. Aaron Hager, Univ. of Illinois.
• Using a residual herbicide in soybeans at a full labeled rate was recommended years ago, and is even more important today.
• Change only happens when biology leaves growers with few or no choices. Thus, a management program must adapt to changing weed biology that is sure to occur when only chemical control is used.
Dr. Stanley Culpepper, Univ. of Georgia
• Palmer amaranth is the no. 1 weed enemy in Georgia agriculture and the no. 1 agricultural pest.
• Results from a grower poll listed timely herbicide applications and residual herbicides as the most important measures for improving pigweed control.
• Resistance and regulation are the two most important issues in future weed management. Sound science should be used to address the regulatory and resistance management challenges that threaten the practical use of pesticides.
Dr. Larry Steckel, Univ. of Tenn.
• Weed resistance to dicamba, 2,4-D, and glufosinate herbicides has already appeared in Tenn. fields.
• Glyphosate resistance in certain grass species is now present.
• When applied together, dicamba is hindering the efficacy of grass-controlling herbicides such as glyphosate.
• PRE and residual herbicides are the backbone of weed control.
• Herbicide technology must be conserved by using cover crops and tillage where appropriate.
• No herbicide cavalry is soon to arrive–i.e. there is no new herbicide chemistry on the horizon.
Dr. Jason Bond, Miss. State Univ.
• Palmer amaranth and Italian ryegrass rate as the two most problematic weeds for Miss. growers. However, ryegrass has increased in importance since dicamba arrived on the scene to control Palmer amaranth.
• Timely application of efficacious herbicides on a large acreage is the key to effective weed management.
• The rapid development of weed resistance to herbicides will continue in the next 3 to 7 years.
• The key to effective weed management for the foreseeable future will be a combination of agronomic innovation and herbicide technology.
Composed by Larry G. Heatherly, Sept. 2021, firstname.lastname@example.org