PP 1/331 (1) Principles of efficacy extrapolations for major uses

Abstract

This Standard describes the principles to be followed when considering effectiveness and crop safety extrapolations of plant protection products applied for major uses. The aim is to reduce the need for trial data on individual major crop and major pest situations, while maintaining appropriate data sets by describing the general principles that should be considered in making extrapolations. The Standard provides guidance for regulatory authorities and applicants in the context of the registration of plant protection products, and for the development of detailed lists of acceptable extrapolations. The Standard does not cover plant growth regulators (PGR) and plant defence inducers. Extrapolations of identical uses between different formulations of the same product are outside the scope of this Standard.1

First approved in 2024–09.

EPPO Standard PP 1/257 Efficacy and crop safety extrapolations for minor uses describes principles of extrapolation for minor uses and is used to support the development of a detailed list of acceptable minor uses extrapolations presented in the EPPO Database on PPP Extrapolation.2 The principles described in the current Standard are closely aligned to PP 1/257 but are specifically aimed at major uses, where a key consideration is a need for a robust dataset for a major use in order to extrapolate to other major uses. The definition of a ‘robust’ dataset, and how to generate the data, is provided in EPPO Standards PP 1/214 Principles of acceptable efficacy, with the number of trials for major uses described in PP 1/226 Number of efficacy trials. The use of data in a zonal context is described in EPPO Standard PP 1/278 Principles of zonal data production and evaluation.

The definition of ‘major uses’ varies between EPPO countries and there is no harmonized definition for the whole EPPO region. Key determinants include factors such as market values and area covered and distribution of the proposed crops, the pest impact and the scale of use of the applied plant protection products. Examples of extrapolations of major pests (with multiple host crops) in minor crops are presented in the minor use EPPO Extrapolation Database for a number of pests (including nematodes, slugs and spider mites) with multiple hosts. Extrapolations may be used either to allow an existing authorisation to be extended to include additional crops (or, in the case of herbicides, other non-crop uses) or pests in the absence of specific data, or to reduce the extent of the data package that would normally be required to support another use. Further information is available in EPPO Standard PP 1/226 Number of Efficacy trials.

Pests that are commonly regarded as major or more difficult to control, and therefore requiring specific data, are particularly relevant as key pests from which to extrapolate. There is potentially significant variability in pest, crop and product interactions, which can affect the validity of any extrapolation. For this reason, a precautionary approach should be taken for major uses, and extrapolations should not be made from less to more challenging control situations. The broader the range of conditions (whether pest or crop related) under which the product has demonstrated acceptable efficacy (and particularly how challenging the conditions were), the greater the scope for extrapolation without the need for additional data.

Extrapolations should be based on applying the plant protection product under comparable conditions of use, for example a comparable dose and timing. It may be possible however to have some flexibility in certain aspects, e.g. number and timing of applications or growth stages of the crop. However, this is dependent on differences not influencing effectiveness or crop safety and should be supported by robust argumentation.

The following sections provide in detail the extrapolation principles for fungicides, insecticides or acaricides, and herbicides, with accompanying decision-making schemes (Appendix 1), and also some information on seed treatments. The list of factors in these schemes is not exhaustive, with mode of action, conditions of use, and extent of existing product knowledge determining whether an extrapolation is appropriate.

It is recognized that there will be other more specialized plant protection products and modes of action that are not specifically mentioned in this Standard, (e.g. bactericides, nematicides, molluscicides and some types of biopesticides), but the same considerations and principles will in general apply. Further information is also available in EPPO Standard PP 1/296 Principles of efficacy evaluation for low-risk plant protection products and EPPO Standard PP 1/276 Principles of efficacy evaluation for microbial plant protection. Plant growth regulators (PGR) and plant defence inducers are outside the scope of this Standard because there can be significant variations in physiological responses of crops to a PGR or a plant defence inducer and extrapolation is generally not possible.

This Standard does not specifically address extrapolations between protected and field situations, but the principles of comparability of the relevant pest and agronomic factors should be considered, along with the relative challenge in each situation when considering both effectiveness and crop safety extrapolations.

Extrapolation between seed treatments of different crops is normally possible when seeding density and thousand-grain weight are similar and if a pest causes similar damage. Different sizes of seeds between different crops may lead to different dilution effects, which may mean that extrapolation is not possible. Other factors of importance should be considered such as the sowing period, the time of appearance of pest, the application technique and the seed morphology. Crop safety aspects for extrapolation between seed treatments on different crops should consider the comparability of factors described above under the effectiveness sections. Considerations should be given to any known additional adverse impacts on aspects of crop safety such as crop emergence, delayed germination, or phytotoxicity to young seedlings.