Controlling Weeds from Day One

According to Helena representatives across the Midwest, growers found more success by adding residuals to their pre-plant burndown than burndown products alone. Without residual control, wet conditions during spring promoted frequent weed germination and heavy pressure, warranting more post-emergence applications. However, the hot, drought conditions that followed during the summer lessened the impact of post herbicides as weeds hardened off, illustrating the need to establish control early.

Pre-emergence herbicide applications lay the foundation for effective weed management throughout the season. Dr. Cox stressed the importance of overlaying residuals with every application and choosing herbicides that provide at least two different modes of action (MOA). Also consider the weed pressure and herbicide resistance in your area and account for weed height at every application.

“It’s no surprise waterhemp escapes were a problem last year,” said Dr. Cox. “It’s very prolific, and size at application is critical. You need to apply any post-emergence application to waterhemp at approximately two inches or less to have a chance at control. You have to play your cards right on the front end, apply those residuals, and try to prevent it from ever coming out of the ground.”

There is cause for optimism when choosing herbicides this year. Supply is not nearly the concern it was this time last year, and prices have declined on raw materials and common products such as glyphosate, clethodim and synthetic auxins like 2,4-D and dicamba. Even though fuel costs have stabilized, domestic freight costs still have the potential to cause some volatility in the market. These lingering issues have no doubt impacted decision making going into this season. Dr. Cox cites a study from Purdue University conducted in late 2022 that reported 44% of growers making changes on their farms are reducing tillage due to the rise in energy costs. As crop production practices evolve, they have indirect consequences. In this case, reducing tillage can put a strain on herbicides and exacerbate resistance, which is an additional factor for growers in this category to consider when developing weed management plans.

Dr. Cox also looked at the role soil conditions play in herbicide performance. Variables such as organic matter, clay content and pH can help or hurt weed control depending on the herbicide’s active ingredient. HyGround® soil management services from Helena measures these and other variables in the soil. The knowledge gained allows for a site-specific approach that places the right herbicide at an appropriate rate on the acre. Timing those applications with rainfall and irrigation can help ensure there is enough soil moisture to activate the herbicide, make it available for weed uptake, and avoid plantback issues the following season.

Finally, Dr. Cox encouraged growers to consider weed control in terms of cost per acre instead of cost per application. Investing in residual applications up front has the potential to save a post application down the line. Instead of cutting back this year, applying herbicides at labeled rates and pairing them with a quality adjuvant is a much better way to see a return on your investment.