With all the talk about herbicide-resistant weeds and how to best control them, using the correct herbicide combination for each field can be challenging. One term we often hear is, to use multiple effective modes of action to control the specific weeds we want to control. Today's marketplace is getting increasingly busy with new trade names being introduced every year–the one thing to keep in mind is that very few new herbicide molecules are coming to the marketplace and this trend will continue for the foreseeable future.

So, what are all these new products you are reading and hearing about? Most new products we see entering the marketplace are products that contain more than one active ingredient and most of the ingredients they contain are often familiar to you.

This type of packaging strategy has been around for decades. One of the most popular products still in use today that was near the front of this was originally called Primextra Light. The “new” version is Primextra II Magnum which is more concentrated than the original product. Regardless, this product is just Dual or S-metolachlor and Aatrex or atrazine. This product is a great example of two good herbicides being added together to form a better herbicide combination that still has a role in corn production today.

Some may think this matching of herbicide active ingredients is just to sell more of one or the other product and just sell more product in general but this is not the case with most multi-active products in the marketplace. Often the products that are sold this way were being tank-mixed on the farm already so the manufactures will put them together to make it more convenient to the applicator and reduce issues at the sprayer by making sure the product formulations are compatible. This can save time, money and reduce leftover product at the farm level, not to mention potential issues in the sprayer.

Another reason herbicide manufacturers may decide to put more than one active ingredient together as a co-pack or already mixed is to increase efficacy. Through research, it has been often shown that if you combine two specific herbicides the sum of weed control can go up dramatically. In the herbicide world one plus one does not always equal two–it may equal a lot more. On the other hand, mixing the wrong herbicides together can result in poor control from both herbicides. Company research helps determine which products will be mutually beneficial to weed control thus helping growers put the correct mix on the field to maximize weed control.

While herbicide combinations can have some great opportunities on your farm, it becomes your responsibility to know what active ingredients are in the products you are using. Some herbicides have rotational restrictions and some do not. Making sure all the active ingredients will be compatible with your future cropping plans is important before making the application. As well, some herbicide groups have a limit on the applications in a given season for various reasons. For instance, a herbicide like Acuron is a great herbicide for corn but knowing it has S-metolaclor, mesotrione, bicylcopyrone and atrazine means that if we need to go in with a later post-emerge herbicide, we are limited to not using any product with mesotrione and we need to make sure if we are adding atrazine we do not go over the total amount of atrazine allowed to a field in any one growing season. There are many more examples of these situations. Being aware of active ingredients and their limitations becomes very important to not only reduce future residual issues but reduce the chances of promoting herbicide resistance on your farm.

Sprayer clean-out is also an area that needs to be looked at when considering what active ingredients are in the combination. One herbicide in the combination might be registered on more than one crop you are growing so cleaning out the sprayer might not be an issue, but another product in the combination may be deadly to the next crop you plan on spraying, requiring an extensive clean out procedure.

Contact your local AGRIS or Wanstead Co-operative Crop Specialist for trusted, expert advice.