Having a plan for pre-emergence weed control in your corn, soybean or cotton fields helps your crop get off to the strongest possible start in the spring. But well before the growing season arrives, it’s important to take time during the winter to adjust your weed control strategy based on the weather.
Winter weather can have a strong effect on weed germination time. Warmer-than-normal winters can combine with factors such as soil conditions, residue and field history to give winter annuals such as marestail, henbit, chickweed and field pennycress a head start. That can threaten productivity and profitability.
Here are the wintertime factors you should monitor and address to improve your spring burndown planning.
Challenges caused by winter annual weeds
Thick patches of winter annuals can create a number of obstacles, including:
- Soil that’s slow to warm, which prevents crops from germinating
- Nutrient competition in the critical early spring period
- Difficulty getting seeds into the ground at planting
- Loss of optimal yields
By preempting these challenges during the winter months, you’ll be in much better shape come spring.
Evaluate the influence of temperature and weather on weed germination time
Soil temperature, not air temperature, is the primary trigger for weed emergence. Consistent freezing locks weed seeds into dormancy. In contrast, unseasonably warm winter spells, or lack of insulating snow, allows upper soil layers to cycle above base threshold temperatures.
Another factor to monitor is soil moisture. Wet soils that prevent you from putting on a pre-emergence herbicide can give weeds a foothold, potentially limiting the effectiveness of the application.
Keep an eye on both soil temperature and moisture. If above-average temperatures persist, make sure you know the optimal window for pre-emergence herbicide application. In general, herbicides work best in moist warm soils between 60 F and 75 F.¹ If soils are under 50 F, too wet or both, you won’t get as much benefit from the application.
Manage crop residue for pre-emergence weed control
Keeping heavy crop residue on your fields can be beneficial for winter weed management in several ways.
Residue reduces weed germination by absorbing and reflecting sunlight. It also insulates soil, preventing it from reaching the temperatures weed seeds need to germinate. Residue also creates a physical barrier that prevents weed seeds from breaking through the soil surface.
If weeds persist despite heavy residue, you might benefit from a tank-mix herbicide application in late October or early-to-mid November. This can knock down small weeds and help prevent a tough-to-tackle mature weed mess in the spring.²
Understand field history and weed seed dormancy
Another tricky detail to manage is the domino effect of weed management decisions in past growing seasons. If winter weeds have built seed banks–which can range from hundreds of seeds to 3,000 or more seeds per square foot of soil–you’re almost guaranteed to have recurring heavy emergence.³
To make matters worse, big weed populations of henbit or deadnettle can harbor high populations of soybean cyst nematode (SCN). In these cases, weeds and SCN can combine forces to significantly stress your crop.
Regular scouting and a combination of mechanical and chemical management practices, such as application of a product from the BASF pre-emergence herbicide portfolio, can help you prevent that type of outcome.
Experts are available to help you manage winter annual weeds. Reach out to your seed retailer, a nearby extension office agent or a seed company professional like your regional BASF representative.
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Endnotes
- Mathew, Sithin, Debalin Sarangi, and Tom Peters. “Getting the Most Out of Pre-Emergence Herbicides: It Starts with Your Soil.” Minnesota Crop News, University of Minnesota Extension, 23 Apr. 2025, https://blog-crop-news.extension.umn.edu/2025/04/getting-most-out-of-pre-emergence.html. Accessed 24 Aug. 2026.
- Werle, Rodrigo, and Lowell Sandell. “Managing Winter Annual Weeds Starts This Fall.” CropWatch, University of Nebraska-Lincoln, 11 Oct. 2013, https://cropwatch.unl.edu/managing-winter-annual-weeds-starts-fall/. Accessed 24 Aug. 2026.
- Fennimore, Steven A. “Weed Seed Biology, Seedbanks and Management.” Weed Science School 2017, University of California, Davis, 19 July 2017,https://ucanr.edu/sites/default/files/2017-12/276001.pdf. Accessed 24 Aug. 2026.
