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T-4- 121 – Regulation of phosphite/phosphorus acid materials represented for use as fertilizers

1. Purpose

Fertilizer – means any substance or mixture of substances, containing nitrogen, phosphorus, potassium or other plant food, manufactured, sold or represented for use as a plant nutrient.

This document provides regulated parties with information regarding the role of the Canadian Food Inspection Agency (CFIA) in the regulation of phosphite (phosphorous acid) materials represented for use as fertilizers.

2. Authority and summary of CFIA decision

The CFIA has conducted an extensive review of the available scientific literature and has determined that phosphite materials, when sold on their own, do not meet the definition of a plant nutrient and thus are not "fertilizers".

In addition, phosphites do not meet the definition of a "supplement" as they do not improve the physical condition of the soil nor do they aid plant growth or crop yield. Based on the documented fungicidal mode of action of these products they fall under the purview of the Pest Control Products Act which is administered by the Pest Management Regulatory Agency (PMRA).

Supplement – means any substance or mixture of substances, other than a fertilizer, that is manufactured, sold or represented for use in the improvement of the physical condition of soils or to aid plant growth or crop yields.

When sold in combination with a plant available nutrient (such as Potassium,Calcium , etc.) these products can be registered under the Fertilizers Act as fertilizer-pesticides providing they are registered or otherwise approved by the PMRA for the pesticide use prior to registration under the Fertilizers Act. For more information on requirements for fertilizer-pesticides please consult Trade Memorandum T-4-102.

3. Phosphite (phosphorous acid) – mode of action

Phosphites are alkali metal salts of phosphorus acid and represent a reduced form of phosphate. When applied to plants, their primary mode of action is fungicidal. The preponderance of scientific evidence indicates that phosphites can be rapidly taken up by plant root systems but cannot be metabolized in the plant. Therefore phosphites do not represent a source of metabolically-available phosphorus, and do not meet the definition of a "fertilizer" as prescribed by the Fertilizers Act.

Furthermore, there is significant evidence that phosphite treatments can have profound negative effects on plant growth and metabolism, by inducing phosphate starvation response in plants grown under phosphate limiting conditions in soil.

4. Roles and responsibilities

The results of discussions with the PMRA have determined that regulatory oversight for phosphite products will generally fall under the jurisdiction of the Pest Control Products Act. Once the PMRA determines that the product is compliant with the provisions of the Pest Control Products Act, a phosphite product that is combined with a soluble plant available nutrient (such as K or Ca) may be registered under the Fertilizers Act and Regulations as fertilizer-pesticide combination.

Proponents of phosphite materials are directed to contact the PMRA to seek registration and/or approval. Once the phosphite is approved under the PCPA for use in combination with a fertilizer, an application to register the blended material as a fertilizer-pesticide under the Fertilizers Act may be submitted to the CFIA. To be granted registration under the Fertilizers Act, the proponent must demonstrate that the pesticide component is in compliance with the PCPA including all applicable pesticide safety precautions prescribed by the PMRA and that the final product meets CFIA safety and labelling requirements . In addition, the label must contain a statement cautioning against application of the product to phosphorous-limited soils due to phytotoxic effects.

5. Contact information

Fertilizer Safety Section
Canadian Food Inspection Agency
Phone: 1-855-212-7695

For questions regarding the PMRA's regulation of pest control products, contact the Pest Management Information Service.

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