existing formulation, further extensive testing is likely to be

required.

Active substances

Consideration should always be given to the impact on bio-

logical efﬁcacy from changes in active substance(s) content.

Generally, these changes are associated with other signiﬁ-

cant changes to the formulation chemical composition and

should therefore be supported by relevant efﬁcacy data.

Some EPPO member countries provide speciﬁc guidance

describing

threshold

levels

the

individual

content

active substance(s), up to which it may be possible to sup-

port

changes

appropriate

reasoned

case.

These

thresholds are based on extensive national experience and

historical data. Guidance should always be sought from the

relevant regulatory authority.

Part I: General factors to be considered and

information required when a change in chemical

composition is proposed

It is essential to have information regarding the nature and

the magnitude of the proposed change. This should include

information on the chemical nature of the co-formulant(s)

being changed (in content, added or removed) and, if rele-

vant, an explanation of their chemical similarity. When

considering the potential impact of any change, information

on the function of formulation components is most impor-

tant, together with the reasons for making any changes.

This applies particularly to the surfactant system. For exam-

ple, the function may be to improve formulation stability in

the spray tank or improve plant coverage and uptake of

active substance in the plant.

It is also helpful to understand the use of the product and

how the active substance is delivered to the target. For for-

mulations that are diluted and sprayed on the crop and/or

weed this may be via uniform distribution on the leaf surface.

Therefore, effectiveness may be modiﬁed by changes in dis-

tribution and absorption on the leaf surface or by changing

the rate of release of the active substance. Crop safety may

be a key consideration, whether for a particular active sub-

stance or for sensitive plants (often horticultural) which are

more susceptible to developing phytotoxic symptoms.

This section details the criteria that determine the catego-

rization of the proposed changes in chemical composition.

It also provides a summary indication of the type of data

required to support the change, which is discussed in more

detail in Part II of this Standard.

Appendix 1 describes more specialized types of products

(or

situations

use)

where

different

factors

are

relevant. For example, for seed treatments the key issue is

retention of active substance on the seed, and this may be

addressed by reference to physical/chemical data; for baits,

addressing any potential changes in palatability may be the

main issue.

Changes in co-formulants which are not biologically signiﬁ-

cant

For these changes, no efﬁcacy data are required. However,

an explanation of the biological nonsigniﬁcance of any

changed co-formulants should be provided, making refer-

ence to relevant parts of Table 1. This should be an integral

part of a justiﬁcation to explain why the proposed change

is deemed unlikely to impair efﬁcacy.

Note that, as a general rule, it is the amount of active

substance and co-formulants applied to the target that is

important and not the content of the formulation itself, i.e.

the in-use diluted formulation.

It should be remembered that the impact of a series of

individually

nonsigniﬁcant

changes

may

cumulative.

Any

comparison

proposed

change

formulation

should always be made with the originally authorized for-

mulation. It is not appropriate to make a series of minor

changes, each without supporting data, with the ﬁnal result

being

substantively

signiﬁcant

change.

the

overall

changes (compared with the originally authorized and tested

formulation) are beyond those considered as nonsigniﬁcant,

then some data will be required to conﬁrm that efﬁcacy is

not adversely affected.

Changes that are nonsigniﬁcant for efﬁcacy, where no

supporting data are required, are given below. The appli-

cant should notify and provide an appropriate explanation

of the nature of the change. For example, it is noted that

co-formulants

with

different Chemical

Abstracts

Service

(CAS) numbers may be chemically equivalent. Equally, for

compounds with identical

CAS numbers, the

degree of

ethoxylation can be signiﬁcantly different. It is up to the

applicant to explain and justify function, properties and

why they are equivalent, and reference should also be made

to the chemistry assessment. Please also note that other cri-

teria are relevant for more specialized formulation types

and certain situations of use (see Appendix 1).

Changes in co-formulants which are biologically signiﬁcant

Signiﬁcant

changes

chemical

composition

are

those

regarded

potentially

having

some

biological

impact,

requiring

assessment

and

supporting

data.

Where

the

change is considered signiﬁcant, data are required to con-

ﬁrm that the performance and crop safety of the proposed

change are comparable relative to the current formulation

composition.

For most formulations, and particularly foliar applied

sprays, the two key components that may affect efﬁcacy are:

•

A change in the solvent system, i.e. moving from one sol-

vent to a chemically different solvent or signiﬁcantly

changing the content of individual solvent(s). This may

For example, ranges up to

10% are commonly speciﬁed. Where

changes are being made simultaneously to more than one active sub-

stance, the cumulative changes should also be taken into account and

reference made to the original authorized product.

Efﬁcacy evaluation

2020 OEPP/EPPO,

Bulletin OEPP/EPPO Bulletin

, 1–7