Regulatory Directive: Pre-harvest Intervals for Grazing and Cutting for Hay of Immature Crops Treated with Pesticides

28 October 1993
Cat. No.: N/A

The purpose of this Regulatory Directive is to request that registrants provide additional residue data so that pre-harvest intervals (PHI) can be established for the safe grazing or cutting for hay of immature crops treated with pesticides.

This Regulatory Directive replaces Trade Memorandum T-90-02 dated April 10, 1990.


Although not an intended use, the cutting for hay or grazing of immature crops is quite common on the Canadian prairies as a "salvage" operation following poor growing conditions or hail damage to cereals, corn, lentils, fababeans, field peas, rapeseed, forage seed crops, etc.

Traditionally, pesticides have been registered for use on such crops grown to maturity. Grazing or cutting of the immature crop for hay has not been considered the intended use and therefore residue information on the immature plant has not been requested in the registration process. A grazing or haying interval is considered in the registration process only if the green matter is to be fed to livestock. Consequently, many pesticide labels are currently silent about grazing or haying. There is no statement on the label as to whether or not it is safe to graze or hay the crop(s) listed on the label prior to maturity. The absence of this information may lead producers to assume that since there is no specific warning with respect to grazing or haying, it is safe to do so.


In light of the above situation, registrants have until 1995 to clearly define, on all pesticide labels, the feeding restrictions of immature crops if there is the potential for such use. This definition will alleviate any questions, assumptions or concerns by the end user with respect to grazing or cutting for hay of pesticide-treated crops.

In the interim, pesticide-treated crops should not be used for feeding purposes unless such use is specified on the product label. Registrants of new products, or of products requiring label amendments, are asked to cooperate in providing crop residue and/or feeding data to support label directions regarding grazing or haying. If such data are not available, the product label should have the following restrictions: "Caution: Do not graze the treated crops or cut for hay; sufficient data are not available to support such use."

Definition of Terms

For purposes of this Regulatory Directive the following terms are defined:

  1. Harvest is the cutting of the crop or removal of the produce from the plant. It includes direct-combining, cutting (swathing) or grazing; it does not include swath-combining or baling for hay.
  2. Pre-harvest Interval (PHI) is the time between the last application of the pesticide and harvest. PHI values are usually given in days.
  3. Seedling grass or legume is a grass or legume species in the first year of growth, i.e., from date of seeding to the end of one season of growth.
  4. Established grass or legume is in the second or later season of growth.
  5. Hay is vegetation that has been cut to be fed to livestock at a later date.

These terms may be used on the label to describe grazing and/or haying restrictions following the application of a pesticide.

Data Collection and Submission

The registrant will be responsible for the collection and submission of the required data. The intent of the submission will be to establish minimum time intervals after application when it is safe to feed the green matter of a crop. The data will contain:

  1. Residual data at various time intervals following pesticide application. The time intervals selected will be at the discretion of the registrants. Data on both green and dried hay crops may be required.
  2. The crop should be clearly identified, for example, wheat, barley, alfalfa, bromegrass. Plant species in mixed stands of hay and pasture should also be clearly defined.
  3. Livestock feeding studies may be required if significant pesticide residues (as determined by Health Canada) exist at cutting, grazing or harvest.
  4. The data, together with a proposed interval between last application and cutting or grazing, should be submitted to the Plant Industry Directorate, Agriculture and Agri-Food Canada, and to the Food Directorate, Health Canada, for evaluation.

For more details on residue requirements, the registrants are advised to contact the Food Directorate, Health Canada, with an outline of their proposals including label directions, proposed residue studies and a summary of possible livestock feeding scenarios.


The Plant Industry Directorate of Agriculture and Agri-Food Canada, in consultation with Health Canada, will be responsible for assessing the data, advising the registrant and ensuring the proper amendment for the label.

Grazing on Industrial Sites

Vegetation on industrial sites (for example, roadsides and hydro rights-of-way) is not intended for animal feeding. However, pesticide-treated areas may be grazed occasionally if this use is indicated on the product label. Data are required to support such a use.

Please direct any inquiries regarding this Regulatory Directive to:

Pest Management Regulatory Agency
Health Canada
2250 Riverside Drive
A.L. 6606D1
Ottawa, Ontario K1A 0K9
Information Service: 1-800-267-6315 (In Canada only)

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