Changes to 2,4-D registrations

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On 3 October 2018, the APVMA suspended the labels of all products containing the active ingredient 2,4-D and replaced them with a permit.

This action has been taken in response to widespread damage to sensitive crops over several years, including grapes, other horticultural crops, summer pulses and cotton.

The permit contains new Directions for Use including changes to application technique, spray quality, timing and the observance of mandatory no-spray buffer zones as well as the requirements for an increased level of record keeping. These changes do not restrict any other aspects of the currently approved use patterns as detailed by the product label.

Summary of the new directions

  • Applicators must now use at least a very coarse (VC) spray quality.
  • Downwind buffers now apply (typically less than 50 metres, subject to the rate and product being applied).
  • Additional advisory statements have been added for use during the period between 3 October and 15 April:
    • to use an extremely coarse (XC) or ultra coarse (UC) spray quality; and
    • to take further steps to mitigate the risk of spray drift including increased water rates and slower application speeds.
  • Clearer instructions have been added about identifying surface temperature inversions to help avoid spraying when they are present.
  • Additional requirements for detailed records to be made within 24 hours of application that must be kept for a minimum of two years.

Nozzles for very coarse, extremely coarse and ultra coarse

For many grain growers the requirement for using a very coarse (VC) spray quality or, where recommended, extremely coarse (XC) or ultra coarse (UC) spray quality, will require an additional set of nozzles.

Photo of boom spayer
Boom sprayer. PHOTO: Brad Collis

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 orifice sizes most commonly used, which range from 02 (yellow), 025 (lilac) and 03 (blue).

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. These nozzles should be operated at pressures above 4 bar (ideally 5-6 bar), so their use may require increasing the application volume. See below for examples of nozzles that can produce VC (green), XC (white) and UC (black) spray qualities.

Nozzle options for pulse width modulation systems

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 orifice sizes may be appropriate if using the Wilger DR nozzle types.

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

Adjusting application volumes

When increasing the droplet size, it is important to consider increasing the total application volume to maintain coverage and efficacy. In low stubble environments a minimum of 70 litres per hectare has been shown to provide acceptable efficacy when using XC spray qualities. In heavier stubbles this may need to be increased to 80L/ha or more.

Table of spray nozzles
TABLE 1 Spray qualities for common nozzle types and orifice sizes.