Droplet size classification

11 December 2018

Following the October 2018 suspension of 2,4-D labels and release of new label instructions under PER87174, there has been some misunderstanding regarding the instructions around the droplet size classification required under the permit.

Under the 2,4-D permit PER87174, there is an instruction to apply this herbicide with a nozzle that produces at least VERY COARSE spray droplets to minimise the impact of spray drift with this herbicide. This nozzle classification is according to the ASAE S572.1 definition. The APVMA recognises five different standards for droplet size classification (three versions of ASAE, BCPC and ISO), however ASAE S572.1 version is quoted in the permit since it is the most widely accepted standard used by industry. It is important to note that all five nozzle classification standards are compliant with the new 2,4-D instructions.

Following the release of the 2,4-D permit, there has been some criticism associated with using the ASAE S572.1 standard for a number of reasons, including incorrectly perceived changes in testing protocols between standards leading to changes in spray quality. All five standards are based on spraying water only. Further explanation of the different standards for droplet size classification can be found in the technical note on standards for the classification of nozzles in Australia.

Overall, the implementation of new instructions for 2,4-D has been largely embraced by industry, who have recognised and accepted the importance of correct nozzle selection to minimise spray drift of 2,4-D. Whilst S572.1 should be followed in accordance with the new 2,4-D instructions, all ASAE, BCPC and ISO standards comply with the updated label instructions.

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