Kit de Herramientas para el Registro de Plaguicidas

#1102 Efficacy data – Minimum effective dose tests

Objective of the study

In the interest of avoiding undue negative effects of plant protection products on the health of farmers, farm workers, bystanders or consumers, and reducing exposure of the environment, it is important to ensure that only the minimum dose of a product is applied to achieve the desired effect.

Efficacy testing should therefore have as a key objective to determine the minimum dose of a plant protection product necessary to achieve sufficient efficacy against the target pest across a broad range of situations in which the product will be applied. This is referred to as the “minimum effective dose” or the “lowest effective rate” and should be the one recommended on the product label.

The minimum effective dose can be defined in terms of level, duration and consistency of control, or a combination of these. It will be specific to crop/pest combinations and pest management or agronomic practices. In some cases an effective dose range rather than a single dose will need to be determined.

To establish the minimum effective dose, it is necessary to demonstrate that it provides one or more of the following:

  • a higher level of effectiveness compared to a lower dose
  • a longer persistence of action compared to a lower dose
  • a more consistent performance under variable conditions compared to a lower dose


Circumstances in which the study is required

It is generally necessary to conduct field trials for the minimum effective dose for all major crops, pests or uses.

For minor uses, a justification for the dose recommendations, other than minimum effective dose trials, may be sufficient (e.g. based on preliminary screening tests or extrapolation). The registrar will need to consider this on a case-by-case basis.


Test conditions

In order to establish a minimum effective dose, a series of different application rates should be included in the trial programme, to demonstrate the difference in efficacy between lower doses and the proposed one. At least one lower rate than the recommended one should be included in the trials series. Ideally, the recommended rate and approximately 75% and 50% of this rate should be tested. Inclusion of higher rates is normally not necessary, although such information may increase confidence in the results obtained. The number of trials in which the lower rate(s) are included should be sufficient to cover the range of situations for which the product is proposed.


Test substance

Preliminary range finding or screening tests are generally conducted with a formulated product, though not necessarily the one for which registration is sought.


Test organism

The target (pest) organism should in principle be present at levels of agronomic importance, or expected to be present at such levels during the treatment.
The organism must be identified by its full scientific name (whenever possible) and, where relevant, subspecies, variety, isolate, etc. should be stated. Growth stage of the pest, as well as its density, level or frequency of infestation or infection should be noted and be quantified, whenever possible.
A naturally occurring infestation or infection in the plots is preferable, but if artificial inoculation of a pathogen or introduction of a pest is carried out, the applied procedures must be described.

Trial series should include different growth stages of the target organisms where relevant. They should include different strains or races where these are likely to show different degrees of susceptibility to the product.


Testing guidelines

The following guidelines may be used on establishing a minimum effective dose: