T-4-121 - Requirements for Phosphite and Phosphorous Acid Materials Represented for Use as Fertilizers

June 2009

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1. Introduction

1.1 Purpose

This document describes the safety and efficacy requirements for phosphite and phosphorous acid materials imported into and sold in Canada as fertilizers. The information and data outlined in this document must be submitted by all applicants requesting a pre-market assessment and approval of their products.

1.2 Background

All fertilizer and supplement products sold and imported into Canada are regulated under the authority of the Fertilizers Act, which is administered by the Canadian Food Inspection Agency (CFIA). Pursuant to the Act and Regulations, all regulated products must be safe (with respect to human, animal and plant health, as well as the environment), efficacious for the intended purpose, and properly labelled to ensure truthful representation of the product in the marketplace. Phosphite and phosphorous acid materials represented for use as fertilizers are not subject to registration under the Fertilizers Act. However, these products are still subject to regulation, and once in the marketplace, must meet all the standards as prescribed by the Fertilizers Act and Regulations.

For products that do not require registration, compliance with the prescribed standards is verified by the CFIA as part of a voluntary pre-market assessment and product approval process and/or through the administration of marketplace monitoring programs, which include product inspection, sampling, analysis and label verification. Non-compliant products found in the Canadian marketplace are subject to regulatory action which may include product detention, and in cases of severe or repeated contraventions, prosecution.

Product proponents wishing to sell products that do not require registration, but are still subject to regulation, may request a pre-market assessment of their products from the CFIA to ensure compliance with the requirements prescribed by the Fertilizers Act and Regulations.

1.3 Phosphites as Fertilizers

Phosphites are alkali metal salts of phosphorous acid and represent a reduced form of phosphate. When applied to plants, their primary mode of action is fungicidal. Representation and use of phosphite-containing products as fertilizers, and as sources of plant nutritional phosphorous, has been a subject of ongoing controversy. There is a body of scientific evidence that suggests that phosphites can be rapidly taken up by plant root systems but cannot be metabolized in planta. As such, phosphites do not represent a source of metabolically - available phosphorous. Furthermore, there are numerous reports indicating that phosphite treatments can have profound negative effects on plant growth and metabolism, especially when underlying nutritional phosphate levels are suboptimal.

Given the lack of scientific literature supporting phosphite as a source of nutritional phosphorous, those wishing to obtain pre-market approval for products containing phosphite or phosphorous acid materials that are represented for use as fertilizers are required to submit safety and efficacy data, as detailed below, to document the effects of their product(s). Products found in the marketplace that have not been assessed and approved by the CFIA may be subject to regulatory enforcement action, such as, but not limited to, product detention.

2. Administrative Requirements

In addition to the efficacy and safety data requirements outlined below, the following administrative elements must be submitted as part of the voluntary pre-market assessment:

• Cover letter outlining the purpose of the submission
• Three copies of the marketplace label (including application rate, timing, frequency and method of application)
• Designation of signing authority (refer to Trade Memorandum T-4-95 - Signing authority)
• Complete list of ingredients, including:
  • Chemical Abstract Service (CAS) numbers,
  • Concentrations in the final product
• Detailed description of the manufacturing process

3. Labelling Requirements

Companies wishing to obtain a pre-market approval for phosphite-containing products represented for use as fertilizers are required to include complete directions for use on the product label.

Additionally, the following label precautionary statements will be required for all fertilizer products containing phosphite:

This product contains phosphite and should NOT be applied when soil phosphorous levels are suboptimal, as it may be harmful to plant growth.

Use this product only after determining that phosphorous levels are adequate, through soil and/or plant tissue analyses, OR apply this product in conjunction with a fertilizer that contains an available form of phosphate.

Do NOT apply near waterways.

4. Efficacy Data requirements

4.1 General Requirements

Companies wishing to obtain a pre-market approval for phosphite-containing products represented for use as fertilizers are required to demonstrate the efficacy of their products. To this effect, applicants are required to submit efficacy data derived from scientifically valid trials AND/OR a scientific rationale that is based on peer-reviewed literature. The criteria for conducting scientifically valid research trials on phosphite products represented for use as fertilizers are outlined in the following sections. For additional information on conducting efficacy trials to support product approval/registration, please consult Trade Memorandum T-4-108: Efficacy data requirements for fertilizers and supplements regulated under the Fertilizers Act.

4.2 Pest Control

Given the known biocontrol properties of phosphites, all research trials undertaken to support product efficacy must be conducted under active pest management systems. This requirement is intended to separate the biocontrol activity of the product from its effect as a fertilizer (i.e., plant-available nutrient source). This may be achieved either through use of sterile growth media or via application of a broad spectrum fungicide(s) effective in controlling soil borne fungi (e.g., Phytophthora sp.). In addition, disease incidence and severity should be recorded throughout the duration of the trial and included in the data package.

4.3 Soil Analyses

All efficacy field/greenhouse trials on phosphite products represented for use as fertilizers must be conducted under phosphorous-deficient conditions to demonstrate that the phosphite product provides sufficient levels of plant-available phosphorous to satisfy the nutritional requirements of the crop. Soil analyses, including soil type, pH and phosphorous level are to be conducted prior to the commencement of the trials and the results are required to be submitted as part of the data package in order to establish baseline trial conditions.

4.4 Treatment Structures

Appropriate treatment structures must be included in order to generate valid data and to meet the efficacy requirements. Treatments required for agronomic trials include: an untreated control and a phosphite treatment. It is strongly recommended that a positive control phosphate treatment of similar grade and application rate to the phosphite product are included in the trial for comparison purposes.

4.5 Experimental Response Variables

Appropriate experimental response variables must be selected to adequately assess the efficacy of a phosphite product. Suitable response variables may include total yield, vegetative growth weight, and root growth weight. On the other hand, use of total phosphorous uptake and/or tissue phosphorous concentration as response variables does not satisfy the efficacy requirements since phosphites have been reported to accumulate in plant tissues as a metabolically-unavailable form of phosphorous.

4.6 Performance Standards

In addition to the above, treatment with the phosphite product must demonstrate a statistically significant response versus an untreated control in 60% of the trials at the p = 0.05 level of statistical significance (the CFIA, Fertilizer Section will accept data analysed up to a 90% probability (p = 0.10) if accompanied by a rationale indicating why this is an appropriate level for the testing conducted). Although not required, it is further recommended that the phosphite treatment be compared to a relevant phosphate positive control treatment and used in the statistical analysis to assess performance.

4.7 Scientific Rationale Requirements

A scientific rationale is acceptable in lieu of field/greenhouse trial efficacy data provided that it satisfies the following criteria:

1. Peer-reviewed journal articles based on field/greenhouse trial efficacy data and a summary of each article submitted, outlining the relevance to the phosphite product submitted for review;
2. The journal articles include statistical analysis demonstrating a statistically significant response to the phosphite treatment as compared to a relevant untreated control. It is strongly recommended that articles be submitted which include a phosphate positive control treatment for comparison;
3. The timing, frequency, rate and method of the phosphite product application, as well as its use pattern are comparable or equivalent to those tested in the peer-reviewed journal article(s) cited; and
4. The formulation of the phosphite product is comparable, or equivalent, to that tested in the peer-reviewed journal article(s)cited.

Please note that peer-reviewed science demonstrating the pesticidal(fungicidal)properties of phosphite will not be considered as evidence to support approval as a fertilizer material.

4.8 Phosphite Materials Represented as Fertilizers with no Phosphorous Claims

Several types of phosphite products are being sold in the market as fertilizers (for example, potassium phosphite and urea phosphite) and do not display claims for phosphorous, but do claim the availability of other plant nutrients. Although these products may not claim phosphorous in the grade, the guaranteed analysis section, or anywhere else on the label, they are still required to demonstrate product efficacy. Additionally, such products may be required to display statement(s)similar to as follows on the label:

"This product contains phosphite and should NOT be applied when soil phosphorous levels are suboptimal. Apply this product in conjunction with a fertilizer that contains an available form of phosphate."

5. Safety Data Requirements

5.1 General Requirements - Scientific Safety Rationale

The CFIA requires that applicants requesting a phosphite product pre-market assessment, demonstrate product safety by submitting a scientifically-valid, properly-referenced rationale that clearly attests to the safety of the phosphite product and all its ingredients. Such a rationale must provide evidence supporting the safety of the product with respect to human health (including worker and bystander exposure), as well as target and non-target terrestrial and aquatic organisms (including plants and animals) and the environment. Guidance on information to be submitted is outlined in the document Trade Memorandum T-4-113 - Guidelines to Safety Assessments of Fertilizers and Supplements and to Information to be Submitted in Demonstrating Product Safety and its supplement T-4-113 (Suppl. 1) - Data Requirements for Product Safety Evaluations: Explanatory Notes.

5.2 Safety Data from Field Trials

Companies wishing to obtain a pre-market approval for phosphite-containing products represented for use as fertilizers are required to demonstrate the safety of their products. As such, safety data obtained from field/greenhouse trials on all crops treated with phosphite or phosphorous acid material will be required to support product safety and obtain pre-market approval from the CFIA. The required safety data must include observations of the general plant health, disease incidence/severity, phytotoxicity effects (in particular, evidence of phosphate deficiency symptoms), positive and negative effects on target and non-target organisms and levels of phosphite accumulation in edible portions of the plant. Food residue analysis for phosphites may also be required depending on the application rates proposed on the product label.

5.3 Additional Required Information

In addition to the scientifically-valid, properly-referenced safety rationale, field/greenhouse trial data and general requirements outlined above, the following information must be submitted:

• Material Safety Data Sheets (MSDS) for ingredients and final product, if available
• Identification of any potential contaminants (chemical and/or microbial) that may be present in the product or its ingredients

6. Contact

If you have any questions, please contact:

Canadian Food Inspection Agency
Plant Health and Biosecurity Directorate
Crop Inputs Division
Fertilizer Section
59 Camelot Drive
Ottawa, Ontario
K1A 0Y9
Canada
Telephone: 613-773-7189
Facsimile: 613-773-7163