Don’t Overlook the Significance of Late-Emerging Weeds

waterhemp young

One of the most significant effects of late-season weeds is their potential to increase the weed seed bank, posing problems for future growing seasons.

Early season weed management is critical for kicking the season off right and stopping problematic weeds before they have the opportunity to compete with crops for resources, reducing yields. However, a season-long approach to weed management is necessary to control weeds no matter when they emerge, even after canopy. These late-emerging weeds can put your fields in danger, hence the importance of season-long weed control.

Due to the focus on the effect of early emerging weeds on yield, it can be easy to overlook management and prevention of late-season weeds. However, ignoring late-season weeds comes at a cost, such as decreased harvest efficiency, reduced grain quality and the potential to negatively affect future growing seasons. 

Some growing seasons are more prone to late-emerging weeds than others. Cooler temperatures and heavier rainfalls foster poor canopy development, providing a favorable environment for late-emerging weeds to grow.i

These weeds are often still green at harvest time, causing more wear and tear on the harvest equipment. This can cause the equipment to break down, delaying harvest, and costing you both time and profit.ii

Late-emerging weeds can also reduce grain quality. “Late-emerging weeds present at harvest increase moisture and foreign material present in grain,” said Frank Rittemann, selective corn herbicides product manager at Bayer. “Weeds reduce the quality or grade of the corn, as well as the market price, which cuts into a grower’s bottom line.”

Another significant consequence of late-emerging weeds is their potential to affect future growing seasons. “These weeds have the potential to produce seeds, which build up in the weed seed bank,” said Rittemann. “Increasing the weed seed bank could become a big problem in future growing seasons if left unmanaged.”

It is important to scout your fields and pull late-emerging weeds before they go to seed. It is also a good idea to identify late-emerging weeds to gain insights about weeds that might be problematic in the future. This knowledge will be helpful while planning your weed control strategies for the next growing season.

For effective season-long weed management, take a zero-tolerance approach:

  1. Start early to eliminate early season weeds. Early season weed control can also reduce the effects of late-emerging weeds, as the crop has less competition for resources and gets a head start on any weeds that might emerge later. If late-emerging weeds are overshadowed by the crop’s canopy, they will be less competitive for resources and less likely to impact yields.
  2. Continue scouting and managing weeds all season-long. While late-emerging weeds might not affect yields this season, they can still add to the weed seed bank and cause problems in future growing seasons.

Bayer Solutions for Weed Management

Once you know which weeds might be problematic in the upcoming growing season, plan on using a two-pass herbicide program for maximum weed control.

Corvus®, followed by DiFlexx® DUO is a great option for starting clean and keeping fields weed-free through canopy,” Rittemann said. “Once the canopy is fully established, late-season weeds become much less of a threat.”

Ensure you’ll start the season with clean fields by making an early season application of Corvus tankmixed with atrazine. Corvus delivers superior control of emerged weeds with residual, lasting up to eight weeks. With as little as a half-inch of rain, Corvus also reactivates to control tough weeds. For the second pass, to keep fields clean and weed-free, use DiFlexx DUO, tankmixed with Roundup PowerMAX®. With multiple sites of action, DiFlexx DUO takes out tough-to-control weeds. Together, Corvus and DiFlexx DUO, with their tankmix partners, provide season-long weed control for both early-emerging and late-emerging weeds.


Always read and follow label instructions. Bayer, the Bayer Cross, Corvus, DiFlexx, and Roundup PowerMAX are registered trademarks of Bayer Group. Corvus is a Restricted Use Pesticide. Not all products are registered in all states. For additional product information please call toll-free 1-866-99-BAYER (1-866-992-2937) or visit our website at www.CropScience.Bayer.us ©2018 Bayer Group, 800 North Lindbergh Blvd, St. Louis, MO 63167.

Work Cited

i Hartzler, B. “Dealing with late weed escapes in corn.” Iowa State University Extension and Outreach: Integrated Crop Management, 2008. https://crops.extension.iastate.edu/cropnews/2008/06/dealing-late-weed-escapes-corn

ii Gee, A. “Green weeds complicate early corn, soybean harvest.” Purdue University, 2012. https://www.purdue.edu/newsroom/releases/2012/Q3/green-weeds-complicate-early-corn,-soybean-harvest.html

Copyright © Bayer CropScience