Coarse spray guide to help reduce spray drift

Growers and advisers can access practical resource to optimise spray efficacy

Weeds, Pests, Diseases
A drift reduction guide for spray operators has been released by GRDC explaining how new restrictions to the use of 2,4-D will impact on-farm applications. PHOTO GRDC

A drift reduction guide for spray operators has been released by GRDC explaining how new restrictions to the use of 2,4-D will impact on-farm applications. PHOTO GRDC


GRDC releases drift reduction guide for spray operators in wake of review of 2,4-D use.


Grain growers and spray operators can now access a practical guide explaining how to maintain efficacy when using coarser spray qualities in line with new restrictions to the use of 2,4-D.

The guide has been developed by the GRDC to assist industry understand the on-farm implications of the Australian Pesticides and Veterinary Medicines Authority (APVMA) decision to suspend the labels of all products containing the active ingredient 2,4-D from October 4 2018, replacing them with a permit.

The action by the APMVA was taken in response to widespread damage over several years to sensitive crops, such as grapes, horticultural crops, summer pulses and cotton.

The APMVA permit will stay in place until the finalisation of the 2,4-D review. Public consultation on the review was expected to start late in 2018.

SEE ALSO: Growers urged to focus on minimising risks of spray drift this season

Under the permit, there are changes to the directions for use for 2,4-D including:

  • Changes to application technique, spray quality and timing
  • Observance of mandatory no-spray buffer zones
  • Increased requirements for detailed record keeping.

Industry spray specialist Bill Gordon, who has done extensive work on best practice application, has helped develop the latest GRDC guide to 2,4-D use, for those working in the paddock.

Mr Gordon says it is important to understand the new changes are primarily targeted at drift mitigation and do not restrict any other aspects of the current approved use patterns as detailed in the new permit (replacing the original product labels).

However, he says the key changes for using 2,4-D under the permit include:

  • Applicators must now use at least a Very Coarse (VC) spray quality
  • When using a boom sprayer, boom heights must be 0.5m (or lower) above the target canopy
  • Downwind buffers now apply (typically less than 50m, subject to rate and product being applied) between application sites, downwind sensitive crops and environmentally sensitive aquatic areas.

Mr Gordon says the new permit also includes an advisory statement for 2,4-D use in cereals, fallow and pasture from October 1 2018 to April 15 2019.

These statements advise operators to use an Extremely Coarse (XC) or Ultra Coarse (UC) spray quality and to take steps to mitigate the risk of spray drift, such as adopting increased water rates and slower application speeds.

Additional record keeping is also required under these changes, so operators now need to update spray records, with greater detail, within 24 hours of application and to keep these records for a minimum of two years, Mr Gordon says.

The permit also includes clearer instructions to help identify temperature inversions to reduce off-target spray risk.

I would advise operators to watch for weather changes and stop spraying immediately if a surface temperature inversion develops or conditions become unsuitable for any other reason.

SEE ALSO: Accurate weather forecasting data underpins best-practice weed spraying

Mr Gordon says the changes would mean many spray operators would have to buy additional sets of nozzles to meet the new requirements for VC, XC or UC spray quality.

In practical terms, many low-pressure air induction nozzles, such as the Teejet™ AIXR or Hardi Minidrift™, are not able to produce VC, XC or UC droplets at useful pressures in the nozzle sizes most commonly used, which range from 02 (yellow), 025 (lilac) and 03 (blue), he says.

Therefore, many spray operators will need to change to high pressure air induction nozzles, such as the Hardi Injet™, Teejet™ TTI or TTI-60, or the Agrotop™ TD-XL-D.

Operators are encouraged to contact their suppliers well before starting spray activities to secure the supply of their nozzle requirements.

These nozzles should be operated at pressures above 4 bar (ideally 5-6 bar), so their use may require increasing application volumes.

If spray operators are using Pulse Width Modulation Systems, Mr Gordon says there are several options to ensure they are meeting the new permit requirements.

Very coarse spray qualities can be achieved on Pulse Width Modulation systems using Wilger™ MR-04 or SR-06 nozzles at pressures below 2.4 Bar. Other nozzle sizes may be appropriate if using the Wilger™ DR nozzle types, he says.

To obtain XC or coarser spray qualities, operators should check with their suppliers on the availability of newer nozzle models that are suitable for this purpose.

Mr Gordon says operators would also need to consider adjusting application volumes when using coarser spray qualities.

When increasing the droplet size, it is important to consider increasing the total application volume to maintain coverage and efficacy, he says.

In low stubble environments a minimum of 70 litres per hectare has be shown to provide acceptable efficacy when using XC spray qualities. In heavier stubbles this may need to be increased to 80L/ha or more.

Mr Gordon says there are additional state and territory restrictions which spray operators and growers must adhere to, and which may include restricted areas and times of use. Operators are advised to check with their relevant state authority for details.

The new GRDC Fact Sheet Maintaining efficacy with larger drops can be found at:

More information: