Chemical application is fundamental to many cropping systems, helping to control weeds, diseases and pests and maximise crop yield and quality. Growers must adopt best practice strategies and equipment to minimise spray drift and off-target damage. They must also recognise the risk of damage to off target crops, particularly sensitive crops in viticultural and horticultural areas.
In May 2018, GPSA launched a new campaign encouraging growers to ‘Hit Your Target’.
In recent years, off-target damage has been an increasing issue in viticultural and horticultural areas, with damage to vines during periods of summer weed control of particular concern. Poor spray practices, such as spraying in certain weather conditions, at high speed or incorrect equipment set-up can result in spray drifting tens of kilometres from the application site.
In previous times, growers have rallied to adhere to the Harvest Code of Practice and to not reap grain when the Grassland Fire Danger Index is above 35. GPSA is seeking a similar response from ‘Hit Your Target’ in which communities of growers work together to minimise the risk of spray drift – and to ensure that these important tools in our cropping businesses can be maintained.
Tips to ‘Hit Your Target’
The campaign points to a number of resources for growers and conveys best practice information to help growers ‘Hit Your Target’ and reduce the likelihood of spray drift and off target damage.
The Grains Research and Development Corporation and Nufarm spray consultant Bill Gordon provide a number of recommendations for growers to help to minimise spray drift.
- Choose products carefully. Understand the coverage requirements plus the mode of action, formulation type and adjuvant used. Read and follow the crop protection product label for what is legally required on spray quality, buffer (no-spray) zones and wind speed requirements.
- Use correct droplet size. Use the coarsest spray quality that will provide efficacy. Be prepared to increase application volumes when coarser spray qualities are used, or when the delta T value approaches 10 to 12. When using any of the Group I herbicides, do not apply with smaller than coarse to very coarse droplets, as per the product label. The minimum droplet size should be 200 microns to avoid spray drift. Nozzle choice is just the first step in drift reduction. Even the best nozzles will cause drift if the remainder of the spraying process is conducted inadequately.
- Never spray in temperature inversions. Always expect surface temperature inversions will form later in the day, as sunset approaches, and they are likely to persist overnight and beyond sunrise on many occasions. If the spray operator cannot determine that an inversion is not present, then no spraying should occur.
- Monitor weather. Use weather forecasting tools and plan. Understand the wind speed and direction. Pay close attention to variations between predicted maximum and minimum temperatures above 5 to 7 degrees Celsius, delta T values below 2, low overnight wind speeds (less than 11 km/h) and predictions of dew or frost as these all indicate the likely presence of a surface inversion. Do not spray with the wind direction toward sensitive areas and do not spray when sea breezes develop.
- Sun. Only start spraying after the sun has risen more than 20 degrees above the horizon and the wind speed has been above 4 to 5 km/h for more than 20 to 30 minutes, with a clear direction that is away from adjacent sensitive areas.
- Boom. Set the boom height to achieve double overlap of the spray patterns. With a 110-degree nozzle using a 50cm nozzle spacing, this is 50cm above the top of the stubble or crop canopy. Boom height and stability is critical. Use height control systems for wider booms or reduce the spraying speed to avoid boom bounce.
- Minimise spray speed. Avoid high spraying speeds, particularly when ground cover is minimal. Speeds above 16 to 18 km/h with trailing rigs, and above 20 to 22 km/h with self-propelled sprayers greatly increase losses and increase spray drift due to affects at the nozzle and the aerodynamics of the machine.
- Buffers. Leave unsprayed buffers when the label requires, or when the wind direction is towards sensitive areas. For ground application of non-volatile products using a coarse spray quality (or larger) during daylight hours and wind speeds between 3 and 20 km/h, a 300m downwind buffer is generally sufficient with a coarse spray quality of larger droplets. However, growers should always refer to the spray drift restraints on the product label. Smaller spray qualities will require larger buffers.
- Record. Always measure and record the wind speed, wind direction, temperature and relative humidity at the start of spraying and at the end of every tank, according to the label requirements. Label no-spray zones and downwind buffer distances are based on wind measurements at 2m above the ground. If possible, check weather station data for temperature inversions.
- Know the risks. Growers must be aware that they are liable. All spray equipment operators have a moral and legal obligation to ensure that their spray applications do not impact other producers, their neighbours or their community. Biosecurity SA will pursue all reports of anyone who has either deliberately or negligently caused damage to others by not following regulatory requirements. If caught, offences can carry a maximum penalty of $35,000.
- Reporting. Reporting is critical to protect crops and achieve statewide compliance. Growers can report off-target damage through Biosecurity SA on the Agricultural and Veterinary Chemicals Hotline on 1300 799 694 or firstname.lastname@example.org
- Resources. Growers need to know what resources they have available to make better informed decisions. Weather stations are an ideal tool to assist with decision-making. Other tools to consider are field weather meters in close proximity to where spraying is being conducted or a hand-held weather meter which can frequently measure conditions in the paddock.
- Crop susceptibility. Growers should have greater awareness of what crops are vulnerable to spray drift. Susceptible crops include cotton, tobacco, tomatoes, vines, fruit trees, vegetables, legume crops and pastures, oilseed crops and susceptible trees, such as Kurrajongs, Belahs and Eucalypts. Growers should also be aware of home garden fruit, vegetables and ornamentals when spraying.