Importance Of Developing An Herbicide Strategy
Developing a sound herbicide strategy is crucial to implementing a solid system to control your weeds.
From weather to resistance, growers are always faced with unpredictable variables. The ultimate goal of your strategy, of course, is to get clean fields and prevent resistance. This requires developing an effective and proactive plan that doesn’t cut corners.
Implementing a Sound Herbicide Strategy
A sound herbicide strategy is built on your fields’ history, knowing what weeds you typically deal with, and identifying any emerging resistance issues.
If you’ve seen emerged weeds in your field, it’s a good idea to get those taken care of with a burndown before planting, especially in no-till situations.
In this In The Field video, Joe Sandbrink, West Central’s Tech Development Representative, discusses a burndown program from a field in New Haven, Missouri that uses Roundup and LIFT Partner BASF’s Zidua® Pro to tackle emerged weeds.
The best way to avoid stress stemmed from weeds is to not allow them to emerge in the first place. Employing a pre-emergence herbicide with soil residual activity can do the initial heavy lifting to take pressure off your post-emergence herbicide application. Combining a labeled soil residual herbicide with a post-emergence application gives you a nice one-two punch against weeds.
Applying a pre-emergence herbicide before the crops emerge can hold weeds off for a while. Factors like rain activation and microbial degradation all limit how long a pre-emergence herbicide will be effective. Often by 30 days a pre-emergence herbicide will begin to lose or will have lost much of its effectiveness.
You may see some weeds starting to grow around this time frame. Scouting can help you catch these escaped weeds before they get out of control and by using a post-emergence spray-on application, you can kill the emerged weeds. Including a labeled post-emergence soil residual herbicide with your post application can further assist your efforts to maximize weed control in the field.
Corey Klaphake, West Central Technical Specialist says: “The idea is to kill any emerged weeds that have made it through the pre-emergence herbicide application and tank mix a second soil-applied residual herbicide to hopefully carry you out another thirty days. By that time, your canopy should be closed.”
The University of Minnesota Extension calls this approach layering residual herbicides:
“To help address these challenges in controlling waterhemp, one strategy is to layer Group-15 herbicides…or a Group-14 herbicide…pre-emergence followed by an additional Group-15 herbicide application about 30 days later (early POST). As illustrated in Figure 1, control from the pre-emergence application declines just as the July flush of waterhemp seedlings is beginning. The second, layered application extends seedling control through peak waterhemp emergence.”
Soil-applied herbicides can help protect throughout the season by staying active in the soil for about thirty days at a time. Soil-applied residuals also help reduce your weed seed bank.
Since weed seeds can remain viable in the soil, under the right conditions they can end up growing. They could be too deep, for example, but tillage might dig them back up and lead to sprouting. Weeds can emerge anywhere from a couple years to five or even ten years.
Over time, residual herbicide will slowly prevent these seeds from growing. If you keep using this program, that seed bank will start to slowly diminish with the herbicide preventing those seeds from growing.
Corey Klaphake warns that “the key thing with these soil-applied post-herbicides is…not everything that you can put down pre, before planting or emergence, can be applied post on crops – due to crop injury potential or other label restrictions.”
“There are a select few pre-emergence soil-applied herbicides, especially when you get into soybeans, that are actually labeled for post-applications. If the weeds are emerged, these herbicides are not going to have any control over them; but they are good at preventing weeds from emerging.”
Several LIFT Partners provide residual herbicides that are labeled for post applications including:
- Outlook® from BASF – Outlook herbicide provides powerful, consistent control of grasses and small-seeded broadleaf weeds such as waterhemp, pigweed and nightshade, while delivering excellent crop safety.
- Zidua® also from BASF – For the past several years, various small-seeded broadleaf weeds and grasses have been growing resistant to different herbicides. Zidua circumvents this resistance, providing growers with effective, long-lasting residual weed control.
- Anthem® from FMC – Anthem controls a broad spectrum of broadleaves — even resistant weeds such as waterhemp and pigweed — and grasses like yellow foxtail, green foxtail and giant foxtail.