In line with the principles of EPPO Standard PP 1/226

Number of efﬁcacy trials,

minor uses and secondary targets

can

addressed

reduced

datasets,

but

again

trials

should

located

cover

the

diversity

conditions

encountered, and especially the more challenging.

In published case studies (Sunley & Zlof, 2011), guid-

ance on numbers of trials, and the justiﬁcation for them is

presented for a series of realistic scenarios.

Situations of more limited diversity

For certain uses of plant protection products, the diversity

of conditions encountered is likely to be more limited. For

example, use of plant protection products in stored grain

other

storage

situations,

and

protected

conditions

where crops may be grown in controlled conditions per-

haps

using

artiﬁcial

growing

media.

Article

Regulation

1107/2009

considers

that

the

case

application for use in greenhouses, as post-harvest treat-

ment, for treatment of empty storage rooms and for seed

treatment, the whole of the EU area is considered as one

authorization zone.

In situations where the diversity of conditions is likely to

be more limited compared to conventional outdoor plant

protection, the applicant should still consider and identify

the different conditions likely to be encountered in the

authorization zone. Testing of the product should occur in

extremes of the conditions encountered to ensure perfor-

mance across the range of conditions. As previously men-

tioned in some situations precautionary label warnings may

be required (e.g. to advise users of possible reduced efﬁ-

cacy where fumigants are used for treatment of leaky rather

than gas tight storage premises) or for example different

doses against the main target species may be required if

there are substantive differences in sensitivity. In the case

of seed treatments, these are subject to the wide range of

soil types and climatic conditions present across the autho-

rization zone, as well as to variation in pest pressure and

sensitivity. As such, it is considered that these treatments

are more similar to conventional foliar plant protection

products and a trials series should encompass the diverse

conditions encountered in the authorization zone.

Some crops may be grown both indoors and outdoors in

the same zone. In such situations and because of the differ-

ence in conditions that protection can bring, efﬁcacy testing

should be conducted in both situations although data from

one condition may

be relevant to the

other (especially

where those conditions result in a more severe challenge to

performance).

Minimum effective dose

EPPO Standard PP 1/225

Minimum effective dose

describes

the criteria, as well as the experimental procedure for deter-

mining the minimum effective dose of a plant protection

product.

Across an authorization zone where there may be sub-

stantial variation not only in climatic and environmental

conditions, but also in agronomy and crop structures, and

in pest pressure and its sensitivity to a plant protection

product,

there

may

variation

the

minimum

dose

required for effective control of a given target on a crop for

those different conditions.

The applicant may already be aware of differences that

might result in the requirement for different doses against

a target (for example if a reference product is authorized

at different doses in different countries for the same tar-

get), and these should be taken into account in the design

of the trials series across the authorization zone. Alterna-

tively

the

effectiveness

trials

may

show

differences

performance

for

certain

conditions,

and

may

warrant

different doses.

EPPO

Standard

1/225

Minimum

effective

dose

requires that in order to establish the minimum effective

dose, at least 1 lower dose than that which is to be recom-

mended should be included in some trials. Where perfor-

mance

may

affected

the

variation

across

the

authorization zone, it is recommended that more than 1

additional dose than that proposed be included in some of

the trials. In this way the applicant may be able to provide

both

sufﬁcient

data

demonstrate

effectiveness

the

appropriate dose for a given set of conditions as well as

justify the dose proposed.

Therefore, where appropriate, and supported by data or

reasoned argument, a different dose may be proposed on

an individual National label for the same target. Further,

the main target may differ on the same crop in different

areas within the zone, so it is important to ensure that

data supporting minimum effective dose are generated on

an appropriate range of target pests or pest pressure within

the crop. The applicant should explain/give an overview

on what the proposed strategy is in terms of rates e.g. 1

dose for the same target across the zone, or proposals

(and justiﬁcation) for varying doses regionally within a

zone.

Use of reference products in a zonal data set

To facilitate comparison of data produced in different con-

ditions across a zone, it is preferable that the same refer-

ence product should be used in the trials. However, it is

acknowledged that in a large zone spanning several coun-

tries, this may not be possible if the reference product is

not authorized for the same uses and rates in all those

countries. In such situations an alternative reference product

may need to be used. It may be beneﬁcial to include both

reference products in some trials for comparative purposes

if this is permitted by available authorizations. It is impor-

tant to note that one of the purposes of a reference product

is to indicate the validity of the trial.

In designing a trial series and considering conditions

across an authorization zone, the applicant may observe that

364

Efﬁcacy evaluation of plant protection products

2012 OEPP/EPPO,

Bulletin OEPP/EPPO Bulletin

, 358–366