Primary Industries and Regions SA (PIRSA) encourages industry best practice when using rural chemicals.
Weather conditions for spraying chemicals
Spray pesticides and herbicides under the appropriate weather conditions to minimise the movement of chemical (drift), increase efficacy and reduce costs.
Spray only when there are:
- consistent light winds, 3 to 20 km per hour (3-15 km/hr for Group I herbicides) blowing away from sensitive areas.
- mild temperatures and high relative humidity.
Surface temperature inversions
Never spray under still or inversion conditions.
During inversion conditions, damaging concentrations of agricultural chemicals can drift for many kilometres and affect sensitive corps. Refer to the Australian Pesticides and Veterinary Medicines Authority for information about surface inversions or Grain Research, Development Corporation (GRDC).
Research the weather before spraying
Before spraying check the weather in your region:
Assess the weather at application site using a weather recording device.
Keep records of your observations.
New 2,4-D label instructions
As of 3 October 2018, the Australian Pesticides and Veterinary Medicines Authority (APVMA) has issued new spray drift label instruction requirement for 2,4-D herbicides.
These instructions now include new requirements relating to droplet size, travel speed, boom heights, buffer distances, record keeping and inversion weather conditions targeted at reducing spray drift from summer weed control.
For information on the new 2,4-D label requirements visit www.apvma.gov.au
Summer weed control code of practice
Follow the Code of Practice for Summer Weed Control to minimise off-target incidents and prevent chemical misuse.
- Specific legal/regulated requirements apply to the use of Group I herbicides
Equipment and spray quality
- Use nozzle types and operating pressures to produce a coarse spray quality or larger,
- Very coarse or extra coarse spray quality is recommended when using glyphosate, MCPA or 2,4-D products.
- Booms should only be 50cm above the top of weeds for a 110˚ nozzle at 50cm boom spacing.
- Do not spray with an application speed over 18km per hour unless boom height is 50 cm or less above the target using coarse spray quality or larger and there are no inversion conditions.
- Spray during the day when possible.
- Do not spray 1½ hours before sunset till 1½ hours after sunrise, unless there is no surface temperature inversion.
- Do not spray under inversion conditions.
- Check for inversion warnings or signs of inversions before spraying and stop spraying immediately if a surface temperature inversion or any other unsuitable conditions develop.
- Spray when wind is blowing away from nearby susceptible plants, crops, houses and towns.
- Spray Group I herbicides during the day when winds are between 3 to 15km per hour and when there is no surface temperature inversion.
- Do not spray 2,4-D and MCPA products when there is little or no wind or variable winds.
Monitoring and record keeping
- Monitor and record application details and weather conditions at the start and the end of spraying e.g. wind speed, direction, temperature, relative humidity.
Chemical use record keeping
PIRSA encourages a high standard of record keeping, even where no legislative requirement exists to do so:
Keeping records of rural chemicals use
Record each application of rural chemicals on your property within 24 hours. Records must be kept for two years.
Minimum best practice requirements
- Date, start time and finish time of application.
- Location where the application was made.
- Product names and application rates.
- Crop or situation and the area treated.
- Spray quality or droplet size applied.
- Spray pressure, nozzle brand, nozzle type, flow rate.
- Weather conditions e.g. wind speed, wind direction, temperature, relative humidity and delta T.
- Name, address and contact number for property owner.
- Name, address and contact number for applicator.
Fill in all fields described below as a minimum (electronic or hard copy).
Users and property
Nozzle type & flow rate
Paddock location or identification
Spray time 00:00
AM or PM
Product name (including adjuvants)
Wind speed km/hr
User contact number
Spray volume (L/Ha)
Product rate / ha
(if different to user)
Crop or situation
Area treated (ha)