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Prowl meets Roundup – Photo by Peter Smith, University of Guelph
Prowl meets Roundup – Photo by Peter Smith, University of Guelph

The ability to apply multiple crop protection products in tank mixtures is an important component of pest management in agriculture, especially for horticultural crops. Compared to field crops, horticultural crops often have more diverse pest complexes which affect them, over a longer period of susceptibility, with a higher cost associated with pest losses due to the increased value of the crop.


All these factors contribute to a greater need generally for crop protection applications in horticultural food crops. Tank mixing provides an important strategy to increase the pest spectrum controlled by a single application, to promote resistance management for one or more active ingredients, and provide time and cost savings to the user.


The benefits of tank mixing are well illustrated with data from the 2022 Ontario processing tomato crop. Producers recorded a total of 2,755 applications to their processing tomato fields in 2022 across a total of 12,394 acres. Each application record consists of one treatment to one field. A little over half ( 57%) were applications of a single product in the tank. A third (34%) were tank mix applications with two products in the tank. A further eight per cent of applications contained three products in the tank, with four products in the tank making up one per cent of applications. If all tank mix applications were made individually, the number of application passes would have increased by 53 per cent!  That’s a lot more trips.


Historically, each specific permitted tank mix combination had to be added to a product label, following review and approval by the Pest Management Regulatory Agency (PMRA). The process took significant resources for all stakeholders to generate tank mix data for each product combination on each individual crop. This came in the form of a label statement on Product X that contained use directions for both Product X and tank mix partner(s), such as Product Y. Labelled tank mixes were often other products marketed by the same company, but not necessarily of competitors.


As the number of registered products grew, the potential number of tank mix combinations outpaced the ability of registrants and PMRA to add every desired tank mixture to the product labels. Something had to give.


In October 2009, PMRA issued a memorandum regarding the use of unlabelled tank mixes of commercial class pest control products used for crop production. In that document, PMRA indicated the agency’s position that users of commercial class products for crop production were permitted to use unlabelled tank mixes. This was based on the conditions that the tank mix use was consistent with the directions for use for each of the tank mix partners when used alone. This gave growers the freedom to use tank mixtures, provided they followed the full labels for each of the individual components.


The guidance provided in the 2009 memorandum provided significant flexibility to growers, registrants, and the PMRA permitting tank mixes without the need for a label amendment. This has been embraced by both growers and registrants, as few labels created since include specific tank mixing instructions.


In December 2022, the PMRA issued a new guidance document on tank mix labelling backtracking on the 2009 position that a general policy permitted the use of unlabelled tank mixes. As outlined in the new document, the federal Pest Control Products Act states that no person shall use a pest control product in a way that is inconsistent with the directions on the label. As a result, in the view of PMRA policymakers, if a label contains no guidance related to tank mixing, then tank mixes are not permitted – even if the complete label directions for each of the tank mix partners are followed. It is worth noting here that this change in view did not result from an identified risk to human health or the environment.


While the importance of tank mixing continues to be acknowledged, for tank mixing to be permitted by PMRA in future, there must be text on the product label that specifically allows for tank mixing. This text may be in one of two forms: a specific mention of the tank mix partners (Product X may be tank mixed with Product Y) or the inclusion of a general label statement that permits tank mixing.


The general statement will read: “This product may be tank mixed with (a fertilizer, a supplement, or with) registered pest control products, whose labels also allow tank mixing, provided the entirety of both labels, including directions for use, precautions, restrictions, environmental precautions, and spray buffer zones are followed for each product. Which is exactly the same conditions as stated in the 2009 memorandum but instead of publishing this once, PMRA will require the statement be added to each and every product label, if the use of unspecified tank mix partners is to be allowed.


Registrants are now in the process of amending each of the currently registered product labels with the new statements, if they wish them to be added – I understand most do. That being said, standard review timelines for such a label amendment at PMRA is five months. No question that updating every product label will take some time. Ideally these label updates occur relatively quickly and simultaneously to minimize disruption. But this will be one more change growers will have to look out for in the years ahead.



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Submitted by Chris Duyvelshoff on 6 March 2023