Effectively Using Varro FX for Cross-Spectrum Weed Control

Tough-to-control weeds like wild oats continue to plague wheat growers across Western Canada, triggering the need for easy-to-use wild oat control solutions that address Group 1 grass resistance. Available for the 2024 growing season, Varro^® FX is the newest cross-spectrum herbicide option from Bayer for spring and winter wheat. With an enhanced Group 2 formulation, growers can count on improved handling, mixing, and an easier tank and boom cleanout experience. Varro FX delivers excellent control of key weeds including wild oats, kochia, volunteer canola, as well as green and yellow foxtail.

Kate Hadley, a Saskatoon-based Market Development Agronomist with Bayer, worked with local growers to trial Varro FX in 2023. Following her 2023 field experience, Hadley shared some key insights and best practices to keep in mind when using Varro FX.

“Varro FX is the first Group 2 emulsifiable concentrate (EC) on the market in Western Canada. That’s a big change for Group 2 products,” Hadley says. “It rinses out of the chem-handler and boom very easily. One of the growers we’re working with used the legacy Varro formulation for years, so when he tried Varro FX for the first time, he was really surprised by how easy it was to mix, and how well it went through his equipment.”

With a wide application window and cross-spectrum targeting, Varro FX is designed to help growers improve wild oat management. According to Hadley, the trial results verified the product’s value to the market.

“I was in the field with the grower on application day and then 10, 14, and 21 days after application to see how well it worked,” Hadley says. “The results were very strong.”

Varro FX combines the trusted power of Group 2 thiencarbazone-methyl with the addition of Group 4 fluroxypyr for cross-spectrum control of tough grass and broadleaf weeds. With a flexible re-crop, giving growers the freedom to seed all major crops the following season, including in the brown soil zone, it can be tank-mixed with a wide range of cereal broadleaf herbicides for excellent control of many grass and broadleaf weeds.

Identifying the Right Tank-Mix Partner

When determining the right tank-mix partner, the first step should always be scouting your field. In-field scouting throughout the growing and harvest seasons, enhanced by integrating digital tools like FieldView™, can provide helpful multi-season comparisons and performance trends in an operation.

"When you’re scouting, you can use the FieldView Field Regions Report function to map out the parts of the field where you notice high weed pressure,” Hadley says. “That way, when you come back the next year, you can see if the weedy patch has grown or shrunk. Ultimately, that will show you how well your crop protection strategy is dealing with pressures. This information is especially helpful when determining tank-mix partners for Varro FX while monitoring for resistant populations.”

When applying Varro FX, it’s important to pair it with a broadleaf tank-mix partner that stands up well to the weed challenges on your field. Based on the 2023 field trials, Hadley recommends Buctril^® M as a baseline for effective cross-spectrum weed control. Buctril M contains Group 4 and Group 6 active ingredients for consistent control of more than 28 broadleaf weeds.

“Combining Varro FX and Buctril M will give you great control of all the key weed species we’re going after,” Hadley says. “Looking at wild oats, which is one of the more impactful weed species in wheat, Varro FX plus Buctril M has an average 95 per cent control rate when combined in a tank mix. That number rises to an average 96 per cent control rate for annual broadleaf control. While it is a mature broadleaf chemistry product, Buctril M tank mixed with Varro FX is a powerful tool that fits well into resistance management strategies.”

Wild Oats
Untreated	10 Days After Treatment Varro FX + Buctril M	14 Days After Treatment Varro FX + Buctril M	21 Days After Treatment Varro FX + Buctril M
Source: Bayer Crop Science Internal Trial, Eston, SK (2023). Your results may vary depending on agronomic, environmental and pest pressure variables.

For higher weed pressures situations, or when dealing with tougher weeds like cleavers, Infinity^® is a standout option due to its enhanced control of higher concentration broadleaf populations. Other effective tank-mix options include Thumper^®, MCPA Ester, and 2,4-D Ester.

Kochia Control
Untreated	7 Days After Treatment Varro FX + Infinity	14 Days After Treatment Varro FX + Infinity
Source: Bayer Crop Science Internal Trial, Melita, MB (2023). Your results may vary depending on agronomic, environmental and pest pressure variables.

Hadley also notes, “When you plan to spray Varro FX with a tank-mix partner, a lot of growers instinctively add a surfactant to their spray budget. With the new formulation, a grower using Varro FX no longer needs to worry about adding an AMS or NIS into the tank.”

Maximizing Impact with Varro FX

Much like other cereal herbicides, Varro FX is most effective when applied under the right conditions.

“If you’re dealing with a frost event around spray timing, you want to give the crop a few days to start actively growing again before spraying,” Hadley says. “Spraying when the temperature is above four degrees Celsius will ensure your crop is actively growing, alongside your target weed population. Otherwise, aim to apply the product starting at the 8-to-10-degrees Celsius temperature range.”

Varro FX offers a wide application window from the one to six-leaf crop stage. With all weed management strategies, they are most effective when applied early in the window to ensure optimal performance in the “critical weed free period”. Hadley says crop staging is important to keep in mind, but it is also critical to ensure you always apply Varro FX before the presence of the first cereal node.

According to Hadley, “Before you spray a Group 2 chemistry, ensure you’re scouting for node development in the most mature areas of your field to avoid the risk of damaging the developing cereal head.”

Local Bayer representatives like Kate Hadley are available to help you maximize the use of Varro FX, whether it’s to help identify the right tank-mix partner or optimal application timing. To find your nearest Bayer representative or for more information, go to my.bayer.ca and sign up for your MyBayer account today.

“Don’t hesitate to reach out,” Hadley says. “We’re always happy to give a helping hand.”