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Weeds are a constant challenge for farmers, but when they develop resistance to herbicides, the stakes get even higher. For years, the go-to advice was to rotate herbicide groups or mix different modes of action in a single application. While those can still be valuable strategies, this latest approach is making a difference: herbicide layering.
Herbicide layering is about using different herbicides at multiple times during the season to tackle weeds at every stage of their lifecycle. It’s like creating a multi-layered defense for your fields, ensuring that tough, herbicide-resistant weeds like kochia, cleavers, and wild oats populations are managed and seed production is limited.
Why is Herbicide Layering Important?
Herbicide layering is more than just a buzzword—it’s a game-changer for managing weeds and keeping herbicides effective. Here’s why it works so well:
- Slows Resistance: Using different modes of action across the weed’s lifecycle can help minimize the selection pressure against specific herbicide groups
- Covers All the Bases: Targeting weeds at multiple times – that fit the life cycle/characteristics of each weed – reduces the chances of them stealing water, nutrients, and sunlight from your crops
- Boosts Performance: Pre-seed herbicides control the first flushes of weeds, making in-crop treatments more effective (as the population is lower and weeds may be at smaller stages).
- Reduces Future Problems: Managing weeds before they produce seed lowers weed pressure in the future.
It’s all about taking a proactive, big-picture approach to weed control.
How Does Herbicide Layering Work?
It starts with a pre-seed application. This step usually combines a burnoff product to kill early emerged weeds with a soil-applied herbicide to prevent new weeds from emerging. For example, Focus® herbicide (Groups 14 (carfentrazone)and 15 (pyroxasulfone)) works with glyphosate to control tough annual broadleaved weeds like kochia while creating a protective barrier in the soil against germinating grass and broadleaved weeds.
The pre-seed application can be followed by an in-crop/pre-harvest application to tackle any weeds that slipped through the cracks or emerged later. Finally, a post-harvest fall treatment targets perennials and winter annuals, setting your fields up for success in the spring.
This layered approach doesn’t just manage the weeds you see now—it helps delay resistance in your fields.
Steps to Get Started with Herbicide Layering
If you haven’t already given herbicide layering a shot, here’s how to get started:
- Know Your Weeds: Identify what’s growing in your fields. Early emerging annual weeds and stubborn perennials need different approaches.
- Timing is Everything:
- Pre-seed: Apply a soil-applied and burnoff product combination pre-seed or pre-emergent to manage early-emerging weeds and prepare a clean seedbed.
- In-Crop/Pre-Harvest: Apply post-emergent treatments to control later flushing weeds and/or weed escapes from the pre-seed herbicide application to minimize water, sunlight and nutrient competition while the crop is actively growing. Pre-harvest applications may help prevent viable weed seed production.
- Post-Harvest/Late Fall: Apply herbicides to target perennials and winter annuals as they prepare for winter. Later fall soil-applied herbicide applications will help control emerging weeds the following spring.
- Mix It Up: Use herbicides from different chemical groups at each stage to disrupt weed cycles.
Don’t Forget the Bigger Picture
While herbicide layering is an excellent tool, it works even better as part of a bigger plan. Combining herbicide layering with practices like crop rotation, cover crops, harvest weed seed control and strategic tillage can strengthen weed management while reducing reliance on herbicides.
Why Glyphosate Needs Backup
Glyphosate is great at killing emerged weeds (that aren’t glyphosate resistant…), but it doesn’t provide soil residual activity. That means later flushing weeds can appear quickly. Adding a soil-applied herbicide to your pre-seed glyphosate application prevents labelled weeds from emerging through the critical early growth stages, giving your crops the best shot at success.
The Bottom Line
Managing herbicide-resistant weeds doesn’t have to feel like an uphill battle. Herbicide layering gives you a smarter way to stay ahead of weeds, protect crop yields, and keep herbicides working for the long haul. Using different products at the right times sets your fields up for success—not just this season, but for many seasons to come.
For more information, please visit FMC Pre-Seed.
