Tank mixing crop protection products has been an important practice for western Canadian agriculture for a very long time; it allows us to manage weed resistance, control grassy and broadleaf weeds in an efficient one-pass system, and possibly manage nutrition and disease at the same time. The downside is that the chemistries sometimes can be antagonistic to one another and cause gelling in the tanks, or may cause leaf burn or other plant injury or you may encounter efficacy issues.
With in-crop herbicide application timing fast approaching here are some things to keep in mind this spray season:
Tank mix order is extremely important in a lot of situations and is useful to keep in mind when there is no set tank mix order. The WALES acronym is a very common way to determine tank mix order and it goes like this:
- Wettable powders and water dispersible granules
- Agitate tank mix thoroughly
- Liquid Flowables and Suspensions
- Emulsifiable concentrate (ECs) formulations
This acronym can be helpful in determining the safest way to add products to your spray tank. Product labels or your provincial crop protection guide are useful for determining formulations and often offer tank-mix order tips, because there are always exceptions to the rules. Some products have their own special tank mix order, such as certain Group 1 grassy herbicides. Traxos from Syngenta or Puma Advance from Bayer CropScience, for example, are added in second, after the broadleaf herbicide has been added. The common Liberty and Centurion tank mix order doesn’t follow the rules set out by the WALES method, either. Note: Some list Solutions (eg: glyphosate) as being mixed between liquid flowables and ECs, so always double check.
Next up is using a water conditioner in conjunction with herbicides. Spray water often has a pH level of above 7, however, many herbicides work best below this pH. What this means, is that certain elements in the water can “tie up” part of the active ingredient load delivering less to the weeds. This results in essentially applying a cut-rate of herbicide. It’s not ideal.
The most common active ingredient known for this is glyphosate, yes, but many Group 1 and 4 active ingredients (and many others) actually perform better at a lower pH. You can combat a high pH issue by tank mixing ammonium sulfate or other water conditioners to keep the spray water pH down.
Keep in mind sometimes this “heats” up the herbicide on the crop and may cause increased phytotoxicity, and also remember that while many herbicides do prefer low pH levels, some products, such as those in the Group 2 family, actually prefer levels closer to a 7. Always remember to ask your local agronomist or retailer about the specifics of the products you are picking up.
One thing I often get asked about is whether herbicide timing is a good time to add in a fungicde. I believe this is a good question to be asking anytime you are going in with a herbicide, but there are definitely some considerations to take into account. The decision largely depends on targeted disease and product choices. Some families of fungicides such as the strobie (Group 11) can significantly heat up a herbicide application causing leaf burning issues, the opposite of what you want to accomplish with a fungicide. Next, you have to ask yourself about what your rotation is like (is it a short rotation?), what the conditions are like (are they conducive to disease?), what is the field history like, what are your yield goals, what is the crop stage and, perhaps most important, if you’re seeing any disease presence at this time. Asking those questions first, before making a decision, can give you a good idea on whether a fungicide application is a good investment at the herbicide stage, keeping in mind that the more times we apply a mode of action, the more pressure we put on the disease population to adapt and develop resistance.