Technical note on standards for the classification of nozzles in Australia

The Australian Pesticides and Veterinary Medicines Authority (APVMA) recognises the following international standards for the classification of nozzles:

  • American Society of Agricultural and Biological Engineers (ASABE):
    • ASAE S572 FEB04: Spray Nozzle Classification by Droplet Spectra
    • ANSI/ASAE S572.1 MAR2009: Spray Nozzle Classification by Droplet Spectra
    • ANSI/ASAE S572.2 JUL2018: Spray Nozzle Classification by Droplet Spectra
  • British Crop Production Council (BCPC) (Southcombe et al. 1997)
  • ISO 25358: Crop protection equipment – Droplet-size spectra from atomizers – Measurement and classification

All these standards define droplet spectrum categories for the classification of spray nozzles, relative to specified reference nozzles.

The main difference between ASAE S572 and S572.1 is that additional categories of ULTRA COARSE and EXTREMELY FINE were added in S572.1. There is no difference between S572 and S572.1 that would alter classification for a VERY COARSE spray. The only change in S572.2 to S572.1 is to correct a flow rate error for ULTRA COARSE. Since ULTRA COARSE nozzles are available and used for drift mitigation, the 2,4-D instruction refers to S572.1. This version is also the common standard currently adopted by industry. The APVMA spray drift management policy (2019) also addressed the interpretation of these standards with respect to mitigating spray drift.

A common misconception is that S572 is based on spraying water only and S572.1 is based on spraying a water/surfactant mix, but this is incorrect. The three ASAE standards (S572, S572.1 and S572.2) are based on spraying water only through both the reference nozzles and nozzles to be classified. For nozzles that are claimed to reduce spray drift, or utilise pre-orifices or internal turbulence chambers, a surfactant-water mixture should be used. All three versions of the ASAE standard state that a surfactant-water mix should be used for nozzles that are claimed to reduce drift, not that they must be used.

The addition of a pesticide to water can change the droplet size (and subsequent classification) produced by a nozzle. For example, a nozzle that is classified as VERY COARSE when spraying water only may actually be COARSE when spraying a water-surfactant mix or a pesticide alone.

Wherever possible, it is best to use a droplet size classification based on the actual product to be sprayed; product registrants should prepare and submit appropriate data packages to APVMA in a timely manner for evaluation through existing registration processes.

Since the three ASAE standards (S572, S572.1 and S572.2) state that a surfactant-water mix should be used for nozzles that are claimed to reduce drift, data generated using water only meets the label requirement for spray droplets according to the ASAE S572.1 definition for standard nozzles.

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