Features Herbicides Seed & Chemical
Proceed with caution in tank mixes

In the fall of 2009, Canadian growers were handed an opportunity by the Pest Management Regulatory Agency (PMRA). For the first time, with few exceptions, growers were legally able to use unlabelled tank mixes as long as the products were registered for use on the crop. It was a change that was met with praise by many crop protection companies, researchers and growers. Not only did the new policy mean that growers could increase their efficiency, broadening spectrums to control more pests with fewer passes, but the different modes of action present in tank mixes meant an improvement in resistance management. Now crop protection companies and researchers alike are hard at work with growers to take full advantage of the opportunity, offering advice, expertise and precautions for using their own unlabelled tank mixes.

The change in PMRA’s policy was a reflection of the fact that there are crop protection products on the market that may be safely mixed together and applied to crops, even though these mixes may not be on the product label.

Despite the amount of research and trialling crop protection companies perform, it is still not practical nor feasible for them to pursue label additions for every possible tank-mix combination. Labelled or not, the product manufacturers do know which pesticides can be mixed together safely and how the combinations will affect particular crops.

Seek expert advice
As such, access to experts and advisors in wake of the policy change is vital, says Clark Brenzil, provincial weed specialist for the Saskatchewan Ministry of Agriculture. “The best advice I can give to producers interested in trying out their own tank mixes is to consult with the manufacturer,” says Brenzil. “Being able to receive support from those most knowledgeable about their own products will eliminate a lot of the unknowns that producers may otherwise be dealing with.”

For crop protection manufacturer BASF Canada, helping growers determine appropriate tank-mix partners for BASF herbicides and fungicides goes beyond understanding chemical interactions and crop safety. “A main consideration with this new policy is stewardship,” explains Robert Hornford, technical development specialist for BASF. “If growers use the label rate of two active ingredients together, then the chance for resistance is decreased,” says Hornford. “At the same time, using two actives at a reduced rate can do the opposite, so it’s important for growers to be mindful of their mixes.”

Because growers are now able to test certain mixes out for themselves, it is important for the experts to provide guidance wherever possible. To assist with this, crop protection companies are actively increasing communication with their partners to keep growers up to speed on the best path forward when dealing with unlabelled tank mixes. “We now make it a priority for our technical group to develop a list of mixes that BASF can support and send that list out to the major grain companies and co-ops,” says Hornford. “Ultimately, it helps with the growers’ decision making when they’re looking at their options.”

Having access to the experts and the ability to utilize a manufacturer-supported mix has paid off for growers across the Prairies, especially during the wet early seasons of 2010 and 2011. The early disease pressure of this past season created a scenario where a fungicide-herbicide tank mix was a valuable option for growers. Manufacturer-supported combinations have proven to be effective when mixed and applied correctly. “We’ve done the research to support an herbicide-fungicide mix. To be effective, growers must be sure they’re using each product at its recommended rate and within the correct application window,” says Hornford. “To be able to suggest to growers a researched solution, such as Headline and Altitude FX, that saved them significant time and money was tremendous.”

Proper application
Although crop protection companies and researchers can point out the beneficial tank-mixes to use, growers should be aware of the precautions. “There are tank-mix combinations that could have negative outcomes for growers,” comments Brenzil. “Mixing two products together could enhance herbicide activity, potentially damaging a crop or, alternatively, two products together could result in a decrease of activity, reducing weed control activity.”

Another consideration that should be made is crop rotation. Combining two different products can affect a grower’s options for the following year. Certain herbicides limit the crops a grower can grow the following year, and mixing two herbicides together can reduce those options even further. This is why it is vital for growers who use unlabelled tank-mixes to refer to each product label for recrop recommendations before moving forward.

Ultimately, like any crop protection product, success with unlabelled tank mixes depends on following the right directions in the right situation. Doing so will increase the effectiveness of unlabelled tank mixes and increase a grower’s return on investment, all while minimizing risk.

Most important, of course, is knowing what those directions are. That public and private sector researchers and manufacturers are available to growers for advice is a crucial factor in making the PMRA’s policy sustainable for Canadian agriculture. “The key to the entire unlabelled tank mix issue is information,” says Brenzil “The last thing we want are growers doing large-scale compatibility studies and discovering something doesn’t work. The more research and the more complete support that manufacturers can offer growers, the better off growers will be.”