What Helps and What and Hurts Herbicide Performance? | Wheat School

Why It Matters

Proper adjuvant selection safeguards herbicide efficacy, cuts costs, and supports resistance management for wheat producers.

Key Takeaways

• Test water hardness and salinity before adding surfactants.
• Non‑ionic surfactants improve stick‑and‑spread; oils melt cuticles effectively.
• Hot, dry conditions favor oil‑based adjuvants for uptake.
• Light, dusty soils increase antagonism; use water conditioners.
• Newer generic herbicides may need extra adjuvant support.

Summary

The Wheat School episode tackles why herbicide performance can falter and how surfactants and adjuvants restore efficacy. Martin Carr, agronomy manager at Winfield United, explains that water quality—hardness, salinity, and dust content—must be assessed before mixing any additive, and that label requirements often dictate which agents are permissible. Key insights include the distinction between non‑ionic surfactants, which enhance stick‑and‑spread on leaf surfaces, and oil‑based adjuvants such as methylated seed oils that melt waxy cuticles for deeper uptake. Environmental factors—hot, dry weather, light sandy soils, and high dust levels—drive the choice of additive, while pre‑burn and in‑crop applications demand different balances between weed control and crop safety. Carr cites practical examples: non‑ionic agents work well on fuzzy weeds like kochia, whereas oil‑based agents are essential under drought‑induced thick cuticles. He notes that glyphosate formulations already contain surfactants, but newer post‑patent generic products often lack built‑in adjuvants, requiring growers to add them. He also warns that resistance pressures now force multi‑mode‑of‑action mixes, making proper droplet size and water volume critical. The takeaway for growers is clear: evaluate water chemistry, soil texture, and current weather before spraying, select adjuvants that match the herbicide’s mode of action, and follow label guidance. Doing so preserves herbicide efficacy, reduces input waste, and helps manage resistance risk.

Original Description

Farmers spend thousands on crop protection products every year, only to quietly lose performance because of factors that can be overlooked. Water quality, surfactants, and adjuvants can make the difference between a successful spray pass and one that falls short.

For this episode of Wheat School, Martin Carr, agronomy manager with WinField United, joins RealAgriculture’s Amber Bell to discuss how surfactants and adjuvants work, how environmental conditions affect herbicide performance, and what growers should pay attention to before filling the sprayer.

Carr says environmental conditions are one of the biggest drivers when deciding which type of adjuvant should be used in a tank mix. Growers may shift from a crop oil concentrate (CoC) to a methylated seed oil (MSO) depending on the weather conditions and how stressed weeds have become.

“When would I want to up it from a CoC to an MSO? A lot of that is based on environmental conditions,” he says.

He explains that non-ionic surfactants are designed to improve sticking and spreading on the leaf surface, helping droplets stay in place and coat the plant more effectively. Oil-based adjuvants, meanwhile, take things a step further by helping herbicides penetrate waxy cuticles that develop during hot, dry conditions.

That becomes especially important when targeting stressed weeds such as wild oats growing in drought conditions, Carr says. In those cases, methylated seed oils can help improve herbicide uptake and overall weed control.

Carr notes that soil texture can indirectly influence herbicide performance as well. Lighter, sandier soils are often dustier and more prone to drought stress, both of which can reduce herbicide efficacy and increase antagonism in the spray tank.

As resistant weeds continue to spread, Carr says growers also need to think beyond simply adding more glyphosate to the tank.

“We’re having to put in other modes of action into the tank… so to get those other modes of actions to work, we do need to make sure we’re using the right quality water, the right droplet size to get the appropriate coverage,” he says.

Website: https://www.realagriculture.com/

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