Tips & Tricks for Controlling Winter Annual Weeds

MLB Baseball starts March 20th. Weed Season has already started.

First at Bat: Winter Annual Weeds.

Winter Annual Weeds emerged last fall, and no doubt, they are going to get a jump on us this spring. Some of the more common species we deal with include Henbit, Common Chickweed, Prickly Lettuce, Marestail, Shepherd’s Purse, and Field Pennycress. They are more prevalent in no-till production systems.

The question everyone is asking is:

Am I going to have to apply my Burndown herbicide program earlier this year?

Based on the evidence at hand, the answer is most likely, "Yes!" 

📸: BASF employee/Featuring Henbit in central IA. A tough-to-control winter annual weed.

Controlling Winter Annual Weeds Early

We all know that smaller weeds are more easily killed than big ones; spray coverage will be better; dead weeds don’t remove precious moisture from the soil; and the seed bed will be better with smaller, dry, dead weed carcasses than large ones. 

Winter annual weeds break dormancy early and are susceptible to herbicides whenever they are growing. Burndown may be slower, but good control can be achieved when sprayed in “warm and sunny” conditions. Shoot for days where the low temperatures are not expected to dip below 40 ºF.

Sharpen^® herbicide can improve control

Traditional burndown applications of either glyphosate or 2,4-D can be dramatically improved by adding Sharpen^® herbicide to the mix. Sharpen^® herbicide is labeled to control up to 6” pennycress and suppress up to 3” henbit. Other early germinating annual broadleaves, like giant ragweed and lambsquarters are easily controlled by Sharpen herbicide too. Make sure to use the right additives: MSO (1 gal/100) and AMS (8.5–17 lbs/100 gal). Use enough water to get good coverage; I prefer at least 15 GPA and a nozzle that delivers medium-sized droplets. Please reach out to your retailer or your regional BASF representative if you have specific nozzle questions.

📸: @BanksPhotos via Canva/Featuring Sharpen^® herbicide application prior to crop emergence.

Remember, you can’t kill dead weeds

I have run into cases where herbicide non-performance is alleged on winter annual weeds only to find that when I get there, the “problem” weeds were headed out when they were sprayed. Herbicides can only control actively growing weeds. After completing their life cycle, weeds are essentially dead; it takes time for them to dry up and go away. Post-herbicides won’t speed up that process. This will be something to look out for this year because of the early growth. Some winter annuals are already blooming!

Burndown Spray Tip: Spray Additives

The use of oil adjuvants can increase herbicide uptake and improve performance in challenging conditions, e.g., cool temps, slow-growing weeds, and large weeds. 

Do NOT be tempted to replace real nitrogen fertilizer sources. N-replacement products and water conditioners do not offer the same level of control as AMS or UAN. Check herbicide labels!

Always read and follow label directions. Grow Smart and Sharpen are registered trademarks of BASF. Copyright 2024 BASF Corporation. All rights reserved.

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