Herbicide resistance limits the options available to control harmful weeds that are common in soybeans, but one or two ineffective herbicides is only the tip of the iceberg. Recently, waterhemp populations have shown resistance to six different herbicides: 2,4-D, atrazine, chlorimuron, fomesafen, glyphosate and mesotrione, leaving only dicamba and glufosinate available as viable chemical methods of control.
Farmers must begin to think of weed management more holistically and adopt broader methods of control, or resistance is just one of many problems that could arise.
The key to preventing resistance in one — if not multiple — herbicide modes of action is a diversified management strategy, including a combination of cultural, mechanical and biological controls.
Weeds Are (Not) The Champion
Decisions like crop rotation, seed selection, planting and seeding rates, and row widths all can make or break your crop’s ability to suppress the reproduction ability of weeds and slow weed growth. Making proper management decisions gives your crop a competitive advantage over weeds.
Cover Up and Knock Them Down
Cover crops keep the ground covered while cash crops are not in the ground. By holding the soil in place, they prevent soil erosion. Cover crops also improve soil structure and enhance soil nutrients. While all of these are beneficial on their own, cover crops also contribute to weed suppression.
Tillage is also an effective means of weed control but should not be the first option in areas susceptible to wind or water erosion. If chosen as an approach to control, tillage methods should be changed regularly to prevent buildup of a particular species or group of weeds in the soil.
Think About the Long Game
In-season management of weeds and herbicide resistance is important. Employing long-term strategies focused on delaying the evolution of resistance and reducing the population of weed seeds is also key to handling weeds. This means managing the seed bank and limiting weed seed production to keep resistant genes from spreading.