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Registration by analogy is a basic registration approach where a limited comparison is made between a pesticide product submitted for authorization in a resource-limited country and a similar product in one or more reference countries.

Since the product is registered in the reference country, it is assumed that pesticide quality, efficacy and risks are acceptable in that country. The registration authority subsequently evaluates whether the efficacy and risk of the same pesticide are also likely to be acceptable in its own country.

This approach applies bridging methods for the evaluation of efficacy and risk of the pesticide and is relatively less complex, uses fewer data and requires less human resources than a complete evaluation. However, registration by analogy is also less precise than a more comprehensive evaluation and may leave considerable uncertainties about efficacy and risk under the local conditions of use. Therefore, whenever the registration authority is in a position to conduct more comprehensive evaluations, it is recommended that these progressively replace registration by analogy.

The main steps in assessing whether registration by analogy is feasible are schematically shown below.

For evaluation by analogy, ideally a comparison is made between identical pesticide products, from the same manufacturer. Registrars should therefore first look for reference countries where identical products have been registered. However, very similar products may also qualify for registration by analogy.

As a second step, the pesticide use pattern is compared between the reference country and the local situation. This includes the crop or use situation, pest, application rate and frequency, and withholding periods, if any. The use pattern is normally summarized in the Good Agricultural Practice (GAP) table. The comparison of use patterns helps to evaluate whether the efficacy in the local situation can be expected to be similar – or better – than in the reference country.

Subsequently, the potential for adverse human health and environmental effects is compared between the reference country and the local situation. This is done by comparing use patterns again, but now with the aim to assess the likelihood of human or environmental exposure. Any use restrictions, personal protective equipment and environmental precautions are also taken into account. This leads to a conclusion whether the risks in the local situation can be expected to be similar – or less – than in the reference country.

Finally, the registration authority will judge whether it can have sufficient confidence to register the pesticide for a specific use or uses, by analogy to the registration in the reference country.