It’s no secret that weed escapes are an unwelcome presence in crops, often rearing their ugly heads at critical growth stages and depriving your crops of life-sustaining nutrients.
Don’t have the time to get into the weeds of researching how to manage weed escapes? We’ve put together some quick and dirty tips to help you get ahead of the game with both early- and late-season weed control.
Tips for implementing early-season weed control
While it would be easy to spray and pray for these pesky escapees to disappear, herbicidal control is not the only option. In fact, herbicides should be considered just one part of a multifaceted, targeted management approach for stopping yield-reducing weeds.
Canopy crop management to mitigate early season weed pressure
Especially in soybeans, dense crop canopies are considered one of the most effective soybean weed management tools: Thanks to those canopies, late-emerging weeds struggle to thrive and are much less detrimental to overall yields than weeds that emerge at the same time as the crop.
In corn, quicker canopy closure and subsequent shading of the ground can reduce weeds, but the effect is typically minimal compared to the effect in leafy crops like soybeans.
Iowa State University researchers found that the majority of waterhemp plants that emerged at the V4 stage of soybean or corn failed to survive to reproduction stages.
This is a huge win in the fight against this problematic herbicide-resistant weed, with the biomass of waterhemp plants that emerged at the V2 stage in soybean fields being reduced by nearly 80% compared to plants emerging at the same time as the crop.¹
Strategies for encouraging canopy density include: increasing plant populations, planting rows perpendicular to the sun’s path, and selecting tall-growing hybrids.
Planting soybeans in narrow rows (20" or less) is the most effective way to reach the rapid canopy closure needed to effectively crowd out weeds. You’ll want your soybean plants to lap in the row middles as soon as possible, and most importantly before blooming begins.²
Apply post-emergence herbicides effectively
Herbicide coverage and uptake can be reduced when applying to larger weeds, so you’ll want to aim to apply post-emergence herbicides when weeds are in the two- to four-leaf stage or 2" to 3" tall.
Post-emergence corn herbicides
Early-season weed control is typically implemented from V1 to V3 stage but should be completed no later than V6. Broad spectrum control of small grasses and broadleaf weeds can be achieved with Armezon® herbicide or Liberty® ULTRA herbicide. Broadleaf weed control can be achieved with Clarity® herbicide applied early on spike to V2 corn, while Status® herbicide can be applied once corn reaches 4 inch in height.
Soybean post-emergence herbicides
Early weed control is typically implemented prior to V3 and very few post-emergent herbicides can be applied past R1/R2. Liberty ULTRA herbicide can be applied up to R1 for post emerge control of grasses and broadleaves.
For additional residual control Outlook® herbicide can be applied up to V5 while Zidua SC® herbicide can be applied up to V6.
If you hit the optimal application window, the yield saved by preventing early-season competition will typically cover the cost of a second post application in most situations.³
If you miss this window, weeds larger than 3" to 4" are more likely to survive an herbicide application due to having more growing points than smaller seedlings.
Tips for managing late-season weed escapes
Late-season weed escapes may not have as much of an effect on this years yield, but they should not be overlooked for the havoc they wreak during harvest and their ability to reduce harvestable yields in future seasons.
Post-emergence herbicides and manual removal of late-season weed escapes
If the weed escape in question is relatively small, targeted herbicide applications or manual removal is the most reliable way to prevent the weeds from infesting a much larger area the following year.⁴
Marestail and Palmer amaranth are prime examples of weeds worth taking the trouble to remove due to their herbicide resistance and the management challenges they pose once established in larger areas. Removing weeds like this prior to setting and dropping seed can significantly reduce weed pressure in future crops.
Though the ideal situation would be to pull and remove seed-producing weed escapes prior to harvest, this is well worth the effort, but not always a realistic option. Control what you can and consider the following:
- If in a small isolated patch, weed escapes can be mowed prior to harvest, which may reduce seed dropped for future crops and also aid in harvesting.
- Do not run weed patches through the combine. This will disperse weed seeds throughout the field you’re in and even carry them over into the next field.
Looking for further guidance on managing weed escapes? Experts are available to help you put an effective weed management plan in place. Reach out to a nearby extension office agent or a professional like your regional BASF representative to learn more.
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Endnotes
- Hartzler, Bob. “Managing Weeds to Protect Crop Yields.” Integrated Crop Management, Iowa State University, 2025, crops.extension.iastate.edu/encyclopedia/managing-weeds-protect-crop-yields. Accessed 21 Feb. 2025.
- Everman, Wesley. “Weed Management.” NC State Extension Publications, 6 Jan. 2022, content.ces.ncsu.edu/north-carolina-soybean-production-guide/soybean-weed-management. Accessed 21 Feb. 2025.
- Hartzler. “Managing Weeds to Protect Crop Yields.”
- Proctor, Chris. “Mid-season Weed Management in Corn and Soybean.” CropWatch, University of Nebraska–Lincoln, 14 June 2019, cropwatch.unl.edu/2019/mid-season-weed-management-corn-and-soybean/. Accessed 21 Feb. 2025.
