Now that the calendar has flipped to 2021, it’s important to evaluate how your weed management program performed in 2020 so you can make informed choices about this year’s inputs. Many people are looking to close the page on the ups and downs of 2020. Unfortunately, it’s not as easy as “new year, new you” when it comes to weed management.

Across corn- and soybean-growing regions, 2020 saw increased weed seed deposits to the soil seed bank from 2019 prevented plant acres, as well as the impact of dry weather on the effectiveness of 2020 herbicide applications. Be prepared for the previous season’s challenges to have lingering effects this spring, like a large weed seed bank and the continued spread of herbicide resistance.

Additionally, a colder-than-normal winter across the Northern Plains and Upper Midwest may mean soils are slower to warm up in those areas this year. This can result in delayed weed emergence and, ultimately, a balancing act between effective herbicide application and cut-off dates for applying some herbicides. Planning for all scenarios can help ensure you’re able to effectively manage early season weeds, or else you run the risk of weeds running roughshod over your fields.

Regardless of your intended crop, uncontrolled weeds will damage yield potential because they compete with young crops for vital resources – water, nutrients and sunlight. It’s important to keep in mind just how quickly this competition between weeds and crops can cause irreparable damage. The University of Nebraska – Lincoln Extension reports that weeds can impact yield potential as soon as they begin to steal sunlight, water and nutrients from the crop, and that can happen before you even realize a weed is in your field.

The impact of problem weeds

• Marestail produces up to 200,000 seeds per plant. These seeds are highly mobile, which result in rapid spread.
• Russian thistle can produce over 250,000 seeds based on plant size. As it tumbles, Russian thistle spreads seeds, which can germinate in virtually any soil temperature in the spring.
• Kochia is an adaptable, prolific seed producer that can be found in every state except Alaska and Florida. It can produce over 30,000 seeds per plant. In addition, herbicide-resistant kochia is rapidly evolving due to short seed life, high genetic diversity and heavy reliance on herbicides for control in minimum- and no-till cropping systems.
• Giant ragweed can produce up to 5,100 seeds per plant. It has an initial competitive advantage over many other crops and weeds due to its early emergence and rapid growth rate.
• Morning glory can produce up to 500 seeds per plant. These seeds have a hard protective coating that allows them to remain viable in the soil for up to 50 years.

These tough-to-control weeds can be some of the most detrimental factors on your yield both this season and in the future. If you get complacent, resistant weeds will become a bigger and bigger issue as escaped weeds go to seed and produce further resistance problems. Get ahead of emerging weeds to prevent them from going to seed and making a deposit into the weed seed bank.

Stay ahead with an integrated approach

A key method for maximizing corn and soybean yield potential is to use a combination of cultural and chemical practices to effectively manage weeds and prevent them from going to seed. This means choosing practices such as tillage and narrow row spacing along with a full-season herbicide program that contains multiple effective sites of action.

When it comes to weed management via herbicides, you need as many layers of protection in place as possible. One wall, or herbicide application, is not enough – you need a moat, a wall and a barbed wire fence to protect your yield from these yield-robbing weeds. Multiple effective sites of action and overlapping residuals set a strong foundation so you can defend your bottom line.

With that in mind, here are the steps you can take to choose the right herbicides for your farm and what impact they will have:

1. Consider which weed species and weed escapes you noticed in your fields throughout the 2020 season and at harvest. This will be important information to help you choose the herbicide applications that will control those flushes this growing season.

2. When evaluating types of herbicides, it’s important to choose those with broad-spectrum control, multiple effective sites of action and residual activity. The right herbicide program will help you stay on top of weeds and avoid spending more money late in the season to clean up escapes.

3. An effective spring burndown will be important to avoid yield-robbing, early season weed competition.

4. To keep fields clean, you should apply overlapping residual herbicides at full-label rates. This holds true even if weather affects timing, as it has in several recent seasons. A pre-emergence herbicide with long-lasting residual can help mitigate an issue if environmental conditions prevent a timely post-emergence application.

The best way to maximize your corn and soybean yield potential is to use the right herbicides applied at the right time to deliver the best results for your farm. This can help you get the most bang for your buck out of your herbicide application.

Ultimately, the bottom line is: Minimizing the number of weeds in a field is good for your bottom line. Less weed competition means more nutrients, sunlight and water are available for your growing crops. This leads to stronger, healthier plants that produce more bushels and, ultimately, more revenue potential at harvest.

Easier to control a seed than a weed

In order to control weeds before they emerge, use a strong pre-emergent herbicide. Weeds are the most vulnerable right at germination, so that is the opportune time to target for weed management.

By overlapping pre-emergent and post-emergent applications of residual herbicides, you can greatly reduce the chance of leaving missed weeds, or escapes, in the field. That’s important because weeds grow quickly. A four- or five-day delay in treating giant ragweed could mean 5-inch-tall weeds that are much harder to manage.

To make sure you are targeting young weeds, plan to determine your herbicide applications based on the problem weeds in your fields.

References omitted but are available upon request by sending an email to the editor.