STARTS WITH THE TANK MIX
Preparing For Harvest
It All Starts With the Tank Mix
Two primary considerations when tank mixing herbicides — mix all ingredients in the proper order, and make sure you are combining products that are compatible when applied to the target weeds in crop.
Follow the simple W.A.L.E.S. method to make sure all components of the mix are added in this recommended order:
- W - Wetable powders (all dry ingredients) are added first to sprayer tank water
- A - Agitate thoroughly to ensure proper mixing
- L - Liquid flowables and suspensions are next
- E - Emulsifiers and concentrate formulations
- S - Surfactant solutions are added last
- Make sure all active ingredients included in the tank mix are compatible. Each herbicide triggers a metabolic reaction inside the plant and depending on the chemistry, they can trigger mixed signals which are actually antagonistic, reducing the effectiveness of weed control measures and may even be harmful to the crop. Always read product labels for details on tank mixing directions.
Herbicide layering involves using two or four herbicides, with different modes of action in sequence during a growing season. The strategy delivers a one-two punch for better control, especially of problem weeds that may not be as susceptible to a single herbicide application. Wild oats and cleavers are examples of tough-to-control weeds.
A tank mix scenario or other program that might include a faster acting contact herbicide with a residual product is a good approach. The first product weakens the weed, while the second follows up with effective control.
Developing a good herbicide rotation over subsequent seasons is important to reduce the risk of selecting weeds that show herbicide tolerance. But the now commonly-recommended layering approach, with multiple modes of action in the same weed control season, and then rotating chemistries through the crop rotation, can be even more effective in the battle against herbicide resistance.
- Start with a proper pre-seeding burndown to control the first weed flush and reduce weed numbers.
- Follow that up with a tank mix or combination of at least three to four different products (the more the better) with different modes of action and residual activity for effective control.
- It's an effective strategy for catching herbicide resistant weeds you may not be aware of, and/or preventing the resistant ones from getting a start.
Just about every herbicide label carries the recommendation to apply products "when weeds are actively growing." While there may be some variations, in general, if it is nice warm day and the sun is shining, the weeds are actively growing.
Cool overcast conditions aren't conducive for plant growth, including weeds. So at cool or even very hot temperatures weed control can be compromised. An ideal temperature range on a sunny day sits between 16 and 24°C . Weeds may be killed slowly below 15°C. Some herbicides may injure crops if applied above 29°C. Avoid applying volatile herbicides such as 2,4-D ester, MCPA ester and dicamba during hot weather, especially near susceptible broadleaf crops, shelterbelts, or farmsteads.
For more specific recommendations consult product labels.
Preparing For Harvest
With harvest just around the corner, many are considering whether they need a pre-harvest application, and if so, what that should be. There are many factors to this decision – crop and variety, crop conditions, variable staging and potential weed pressure.
Crop and Variety
If you are growing a canola hybrid (variety) trait with pod shatter reduction technology, a pre-harvest herbicide or desiccant can help prevent yield loss by reducing the chance of shatter caused by wind damage at this critical time. Further, a pre-harvest application can make straight-cutting easier and smoother by drying down the canola crop.
In pulse crops, the maturity window can vary greatly. To facilitate the maturity process, it can be beneficial to apply either a desiccant or pre-harvest herbicide.
There are two main options available for a pre-harvest application:
- Pre-harvest herbicide(s)
Each of these can do a great job of preparing your crop and increasing the efficiency of your harvest, but which one is best for you?
Desiccants are contact herbicides and rapidly kill above-ground vegetation, thereby preparing the crop for harvest. They do not have any contact or systemic activity, which means that if weeds are a problem in your crop, the desiccant will not kill the root system, allowing for potential re-growth of perennial weeds. Desiccants work quickly, so the crop needs to be mature and ready to come off the field.
Pre-harvest herbicides, on the other hand work through translocation with contact and systemic activity. This means the application will kill the weeds and prevent the regrowth of perennial weeds and reduce the amount of green weed material in the crop. A pre-harvest herbicide works slower than a desiccant, so if the crop is showing uneven stand or maturity, the herbicide will speed up the time to maturity without drying the crop down immediately.
If you are growing a canola crop with pod-shatter technology or a pulse crop, you should probably be considering a desiccant or pre-harvest herbicide. If your stand and maturity are looking pretty even, and you don’t have a perennial weed problem, a desiccant may be the best option for your crop. If, however, your stand and maturity are looking uneven or perennial weeds are problematic in your field, you best option will be a pre-harvest herbicide application.