By Eric Beckett, CCA, ISA Soy Envoy

Soybean farmers considering a rescue treatment of Liberty or another glufosinate-based herbicide to control waterhemp should talk to their trusted agronomist about the root of the situation. How and when were initial weed control strategies implemented, and why did they come up short in keeping waterhemp at bay?

Some questions that need to be considered with honest feedback:

1. Did we start clean from either tillage, cover crops or spring burndown herbicide application?

2. Were effective sites of action to control waterhemp with preemergent residual herbicides utilized before soybeans emerged and then incorporated into the post-emergent herbicide pass?

  • Possible herbicide tank mixes that have proven effective when combined at planting but before soybean emergence include the following herbicide groups: Group 2, 5, 14, 15.
  • Then, in the post-emergent herbicide pass, were overlapping residuals utilized that might include the following herbicide groups: Group 14 or 15?

3. Were full labeled rates utilized at the time of application with consideration to control waterhemp?

4. Was waterhemp targeted at three to four inches in height at the time of application?

5. What adjuvants were included in the tank mix? One specific adjuvant that Liberty requires is ammonium sulfate or AMS. To overcome possible antagonisms from cations in water sources, the pH of the water must be lowered. Generally, two to three lbs. of AMS per acre will overcome this. However, it is important to have water sources tested.

6. Spray tips: Were the correct spray tips utilized to create the desired spray droplets and provide good coverage of desired weeds, such as waterhemp?

We as producers, agronomists and applicators have control over all of the above questions. It’s about controlling the controllables and managing factors such as environmental conditions at the time of application.

Now, back to the original question: Can Liberty or glufosinate-containing herbicide be considered for a rescue application in soybeans?

1. Is the soybean growth stage at or before R1 growth stage?

2. Will application occur within 70 days of harvest?

3. Have there already been two applications in the crop?

4. Have 87 ounces per acre of Liberty already been used in the crop?

If the answer to any of these questions is “yes,” then the answer is no! The label is a legal contract. It explicitly states that if any of these conditions exist, then a Liberty or glufosinate-containing herbicide application cannot occur.

Application of Liberty or glufosinate-containing herbicide after the R1 growth stage in soybeans is not concerned with knocking blooms off the plant or interfering with reproduction growth stages. It’s more about whether there is enough time to reduce herbicide residues within the plant before harvest. Although this may not be of great concern to growers directly, growers should still be concerned because of the bigger picture. If the grain is evaluated for herbicide residues and Liberty is detected, it might be subject to government seizure, import block or penalties. Illinois is already the leading state in the U.S. for raising soybeans. Let’s not interfere with that reputation by allowing weeds to get out of hand or succumbing to the temptation to spray Liberty off-label and out of compliance.

As always, please read, understand and follow all of the guidelines on the herbicide label!

Originally published on the Field Advisor website on Aug. 5, 2024.

About the Author:

Eric Beckett, CCA, is a 2024 Soy Envoy. Currently serving as a Field Agronomist with Illini FS, Eric brings a wealth of experience from diverse roles in agronomy research. His career has encompassed weed science, corn and soybean plant breeding, and work in high-yield corn and soybean environments across Illinois. Based in east central Illinois, Eric oversees five counties and manages eight full-service agronomy retail locations in his current position. In his role at Illini FS, Eric dedicates much of his time supporting agronomy sales and operations staff, collaborating closely with grower customers. He also takes charge of managing Illini FS’s agronomy interns and the On-Farm Discovery program. Originating from Monticello, Eric now calls Philo, home. Apart from his professional pursuits, Eric finds joy in fishing, traveling with his family and engaging in DIY projects around the house. Eric is formally trained as an agronomist, holding degrees from Parkland College and Southern Illinois University in Carbondale. His professional qualifications extend to being an active CCA 4R NMS and a licensed UAV Drone Pilot, highlighting his commitment to staying at the forefront of agronomic practices and technology.

Photo Credit: Eric Beckett, Illini FS

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