Research Highlights

Comparing Herbicides for Giant Ragweed and Waterhemp Control Helps in Decision Making

In this article, you’ll find details on:

• This research project compares herbicides and herbicide mixtures for giant ragweed and waterhemp control in both corn and soybeans.
• The trials are conducted by an independent company, which provides unbiased, third-party data that farmers can use now.
• Farmers can use trial results to select appropriate herbicides for their crop management systems.

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By Carol Brown

Weeds are persistent, determined plants. Scientists across the country continue to search for new herbicide-tolerant crop genetics, management practices and products that help farmers to reduce weed pressure in crop fields.

In Minnesota, Andrew Lueck is comparing herbicides and herbicide mixes head-to-head for control of giant ragweed and waterhemp in corn-soybean rotations. He is the owner of Next Gen Ag, an independent contract research company he founded in 2017, located near Renville, Minnesota. Next Gen Ag conducts third-party, unbiased, replicated trials for agricultural companies and their products including herbicides, pesticides, fungicides, biologicals, seed treatments and more. 

The Minnesota Soybean Research and Promotion Council (MSRPC) has been working with Lueck for eight years and has supported approximately 50 trials during this time. In 2023, MSRPC funded three grants with Next Gen Ag: a comparison of variable rate tank mixes for waterhemp control, a comparison of pesticides for soybean aphid control and yield impact, and herbicide comparisons for giant ragweed and waterhemp control.

Herbicide Comparison Trials

“Last summer, giant ragweed populations were strong and the trials went really well,” Lueck says. “We have seen high glyphosate and ALS herbicide resistance in giant ragweed, which helps us to measure efficacy of the products we’re testing.”

Lueck is conducting the herbicide trials using a systems approach, since many farmers grow both corn and soybeans. He tested over 60 products and mixes provided by eight industry partners across both crops. He and his team compared product efficacy on the two weed species in both corn and soybean fields, for a total of four separate trials. 

He applied pre-emergence herbicides to both crops, and post-emergence herbicides were applied at the V4 stage for corn and at V1 for soybean. They evaluated waterhemp populations four times in June and July in both the corn and soybean plots. Ragweed populations were evaluated six times between May and July in both corn and soybean plots (Tables 1 and 2).

“We had favorable rainfall after the plots were planted, and the giant ragweed had good emergence,” says Lueck. “However, there weren’t strong populations of waterhemp this year. After the plots for the waterhemp trials were planted, they received only 2.2 inches of rain between then and 75 days after planting. The populations remained low because the conditions weren’t conducive for intense waterhemp germination.”

Some companies had more options than others for herbicide modes of action, depending on their portfolios, Lueck says. Treatments were similar in both the waterhemp and ragweed trials within the same crop.

“But there were a lot of different modes of action in the herbicides used between the two crops, which is why we’re using a systems approach,” he comments. “The mixing of active ingredients can reduce or slow down herbicide resistance.”

Next Gen Ag offers unbiased, third-party competitor data to farmers. Their results show how farmers can get the best return-on-investment for their production systems. The trials conducted through grant funding are only a portion of Lueck’s business, and he says the grant trials are a good system. 

“The funding from MSRPC supports the labor and supplies, and the industry partners supply the chemicals,” Lueck says. “In exchange, MSRPC receives head-to-head data from trials conducted in the same environment with non-biased researchers doing the work.”

This coming crop season, through MSRPC support, Lueck and his team will again conduct the waterhemp and giant ragweed trials, hopefully with a stronger waterhemp population than last year. He’ll also conduct the soybean aphid and value-added product trials again and begin a white mold experiment in 2024.

Lueck believes his company offers Minnesota farmers quality data that they can use now. The products he tests are available on the market, and he evaluates them at industry-recommended rates for the state. Farmers can share trial results with their local crop consultant or agronomist to help determine a weed control strategy for their system.

Additional Resources

For full reports, visit: https://nxtgenag.com

2023 Waterhemp Resistance Management Programs in Corn-Soybean Rotation – Next Gen Ag report

2023 Giant Ragweed Resistance Management Programs in Corn-Soybean Rotations – Next Gen Ag report

Published: Jun 17, 2024