Supporting label changes for pesticide product use in reduced water volumes


This page describes the procedures and data required to support changes to plant protection product (PPP) labels, to reflect use in reduced water volumes.


For practical and economic reasons it's common commercial practice for end users, to apply product in a volume of water less than that specified on the current label (thus applying the product at an increased concentration). Cross compliance inspections by the Rural Payments Agency (RPA) raised significant anxieties for industry whether, and to what extent, the volume of water stated on labels could be reduced. To make the position clear with respect to individual products, HSE requires that product labels should recommend a range of water volumes in which the product can be safely applied. This can be done by making an application for a label change to HSE.

How to apply

Applications to reduce the minimum water volume on the label must include a non-dietary exposure risk assessment and data, or a case addressing efficacy (see below). The application should be submitted to HSE, where it will be assessed via an amendment to authorisation application and charged an appropriate fee.

Non-dietary exposure risk assessments

Non-dietary risk assessment methods should be used as outlined in the non-dietary human exposure guidance pages. Applicants are required to demonstrate that use with reduced water volumes does not pose an unacceptable exposure risk.

Efficacy and crop safety assessment

Data, or a case based on data, confirming adequate efficacy and comparable crop safety must be provided to justify the proposed reduction in water volume. Data from the public domain may be used subject to its relevance (further information below).

There may be instances where efficacy/crop safety data are not available to support changes in water volume. As long as a case for reduced water volume is made by the applicant we will evaluate the non-dietary exposure assessment and consider granting a 'qualified authorisation' for the reduced volume recommendation. Label text would be required to indicate that efficacy data to support reduced volume have not been provided. This would remain a 'qualified authorisation' until data to support a 'full' authorisation has been found acceptable.

Applicants should note that there are situations (depending on the mode of action, crop and target; (further information below) where reduced water volume spray applications may not be appropriate, since they raise concerns over effectiveness. Examples include uses such as:

  • foliar acting herbicide to small monocotyledonous weed targets
  • foliar fungicides targeting stem base diseases
  • disease control on young onion and leek crops
  • contact acting insecticides to concealed pests; eg, leaf curling/rolling aphids/caterpillars.

Whilst data may be used to support recommendations for reduced water volumes for such uses, HSE would not authorise such recommendations in the absence of appropriate data.

Further information

Further information on qualified recommendations can be found in Efficacy guidelines in Data Requirements. Applicants should note that recent public domain evidence in the form of a report titled 'Spray behaviour and efficacy of herbicides and fungicides applied to wheat at reduced volumes' is available on the Agriculture and Horticulture Development Board (AHDB) website. Whilst this report concludes that water volumes did not influence efficacy in the studies conducted, it also indicates that there are some fundamental reasons why low volumes may result in poorer pesticide performance. Simple reference to this report, therefore, is insufficient evidence for blanket reductions in water volume and applicants should consider and address the specific uses for which reduced application volumes are sought.

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Updated 2024-01-30