As the 2019 planting season is upon us, it’s important to not forget those pesky little things we call weeds. For most farmers in the central to southern Corn Belt, weeds are the most challenging issue they face year in and year out. However, there are several proven strategies to consider when tackling weed management.
We have learned that the ease of single post application comes at a cost. ISU weed scientist Bob Hartzler recently tweeted a chart demonstrating the rising costs of weed control with glyphosate resistance. In his chart, average weed control in 2011 was roughly $15/acre for soybeans and $25/acre for corn. For 2019, those costs are expected to rise to $50+/acre for soybeans and $40/acre for corn. While reducing those costs immediately may not be possible, a strategy that seeks to lessen the weed seed bank in the soil may lessen or limit those costs over time. I recommend the following strategies to help reduce buildup of weed seed in your soils.
Strategies
- Choose the right trait package. Choose a trait package that will allow you to utilize multiple, effective modes of action in your fields over the course of a season. By this, we mean that in post applications you need the flexibility to use multiple herbicides with tank mix partners. So, choose trait offerings that give you this broad-spectrum flexibility.
- Start Clean. Whatever method is best for your situation — tillage, chemical control or both — starting with a clean seed bed is key to season-long success in controlling weeds and weed seed production.
- Pre-emerge applications. Utilize pre-emerge residuals with burndown or after tillage. Applying pre-emerge herbicides when the ground is clean helps catch weeds as they sprout. While many weeds are resistant to certain herbicides, once they have emerged and are actively growing, many herbicides such as group 14, 15 and 27 show good control when applied as a soil residual.
- Post-emergent applications. For post-emergent applications, consider layered residuals. Your strategy should include layering residual herbicides to control late-emerging weeds such as waterhemp and palmer amaranth. Residual herbicides will break down in level of control over time with heat and moisture. It is critical to have a level of residual control that moves deeper into the soil to have the most effective control. In addition, having the option of post-applied herbicides that have an additive effect, such as glyphosate and glufosinate, with layered residuals provides excellent control.
Using these strategies will help control existing weed seed banks as well as reducing future weed seed growth. Consult your Stine agronomist or local weed extension specialist for the right strategy for your farm.