Spraying, spray drift and off-target damage
Spraying agricultural chemicals, whether from the ground or the air, needs to be properly planned and carefully executed, to minimise the risk of off-target chemical movement.
As an agricultural chemical user, you have a legal obligation to ensure that the chemicals you apply stay within the target area.
It is an offence to undertake agricultural spraying which:
- injures any plants or stock outside of the target area
- injures any land outside the target area so that growing plants, or keeping stock on that land would result in contamination, or
- is likely to contaminate any agricultural produce derived from plants or stock outside the target area.
Spray drift and off-target damage
Spray drift is the most common cause of off-target chemical movement. It can injure or damage plants, animals, the environment or property, and even affect human health.
'Drift' is the airborne movement of agricultural chemicals as droplets, particles or vapour (see 'Chemical formulations and vapour drift' below).
Reporting spray drift
If you suspect chemical spray drift has occurred on your property, see Reporting spray drift of agricultural chemicals .
Tips to minimise off-target spray drift
A combination of factors can contribute to spray drift, including the volatility of the chemical, weather conditions, equipment and droplet size. Below are some handy tips to help chemical users minimise off-target spray drift.
- Always read and follow the product label directions, including any restrictions. Many labels now detail weather conditions, droplet size, equipment and spray drift restraints and/or mandatory no-spray zones to help users manage drift.
- Choose a chemical formulation that is less likely to drift off-target (e.g. use amine formulations of 2,4-D instead of 2,4-D high volatile esters which are more prone to drift as vapour during or after application).
- Check for susceptible plants, animals and areas (e.g. stream, bee hives) close to the target area and put strategies in place to protect them from drift (e.g. use a buffer zone or leave an unsprayed buffer next to a susceptible crop).
- Discuss your spray plans with neighbouring properties, particularly if you plan to spray near a sensitive crop or area. This provides them with the opportunity to implement protective measures on their property if needed and can help avoid complaints later on.
- Ensure your equipment is set up and calibrated correctly.
- Use a nozzle or sprayer setting that produces the largest possible droplet size (coarsest spray quality) to reduce the risk of drift without compromising the efficacy of the chemical.
- Before you start, check that the weather conditions are suitable for spraying (i.e. wind speeds between 3-15 km/h, blowing away from sensitive crops/areas, Delta T between two and eight, temperature below 28oC, no inversion layer present). If the weather is unstable or unpredictable, don't spray. Continue to monitor weather conditions while spraying and stop spraying if it turns unfavourable.
Buffer zones and vegetative barriers
Buffer zones and vegetative barriers are valuable tools that can be used to reduce the potential for spray drift when applying agricultural chemicals.
A buffer zone is an area around a sensitive area in which agricultural chemicals should not be applied. The presence of a buffer zone allows spray drift to settle out of the air stream as it travels across the buffer zone before reaching the sensitive area. Prior to undertaking spraying, you should assess the risks and determine an appropriate buffer zone, as it will change from paddock to paddock and from year to year.
The required distance of a buffer zone will vary a great deal and may be different from day to day as you must take into account:
- The product you are using, some require buffer to be used in order to legally use the product. When using products that specify a required buffer distance it is important to make a note that this was observed when making a record of use.
- The type of application equipment as a boom sprayer applying a COARSE droplet size is less prone to drift than a mister applying a FINE droplet size.
- The nature of the sensitive area you are trying to protect as different distances may be required for crops compared to residential housing etc.
- The environmental conditions on the day, especially the wind direction and speed.
A vegetative barrier refers to a row of trees, shrubs or tall grasses that has been planted in strategic lines to reduce the extent of spray drift. They are effective in reducing spray drift by filtering out spray droplets in the air as it passes through their foliage.
A vegetative barrier will not reduce vapour drift or odours associated with spray drift.
A good vegetative barrier should be:
- taller than the target plants or the spray unit used for chemical application
- trees or other plants with foliage that allows sufficient air movement (50% porosity)
- plants with long, thin, rough foliage which are more suitable as a vegetative barrier.
Examples of suitable plants include:
- casuarina or sheoak (Allocasuarina spp.)
- hybrid willows (evergreen only)
- rye corn
- bottlebrush (Callistemon spp.)
- tea tree (Leptospermum spp.).
Vegetative barriers are desirable:
- along crop or property boundaries
- next to sensitive areas (e.g. susceptible crops, residential areas, hospitals etc
- along sprinkler rows, bordering waterways
- between blocks or paddocks.
It is important to be aware of the following limitations of vegetative barriers:
- They are not a substitute for good agricultural practice (GAP). If it is too windy then you should not be spraying as either a buffer zone or a vegetative barrier may not be able to stop drift. They are intended to reduce the risk spraying in nearly ideal conditions and help protect against unpredictable gusts.
- They will not stop vapour drift or odour occurring, this is purely a consequence of the product itself and the weather conditions.
Chemical formulations and vapour drift
Certain phenoxy herbicides (e.g. 2,4-D, MCPA, triclopyr and picloram) are available as amine, salt, or ester formulations. As phenoxy herbicides and formulations act differently, it's important to understand their characteristics to help manage the risks associated with their use.
The biggest difference between amine, sodium salt, or ester formulations is their potential to produce vapour. Amine and sodium salt formulations of phenoxy herbicides do not produce vapours at normal application temperatures, whereas ester formulations do.
Under normal operating temperatures, amine formulations can only drift as droplets, which is generally limited to relatively short distances of up to a few hundred metres, though this distance can vary depending on the application method. Amine formulations may produce vapours if the temperature rises to around 50oC, which is an unsuitable temperature for spraying.
Both High Volatile Esters (HVE) (ethyl, butyl and isobutyl esters) and Low Volatile Esters (LVE) (hexyl, octyl etc) can produce vapours after application under certain conditions, and can drift as an invisible vapour for many kilometres, damaging non-target crops and areas. This makes these herbicides a high risk option.
Many valuable crops including vines, cucurbits (melons, pumpkins and zucchinis), tomatoes and fruit trees are highly susceptible to volatile ester herbicides, hence the consequences of spraying these formulations nearby would be significant.
To determine whether a herbicide is an ester formulation, read the active constituent on the product label. If 'ester' appears anywhere in the active constituent name, the product is classed as an ester formulation.
Above is an example of a product label. One of the active constituents in this product is MCPA present as an ester. Therefore this product is a 'restricted use' chemical and an ester formulation.
Please note: As of 21 August 2013, the supply of 2,4-D HVE products has been suspended by the Australian Pesticides and Veterinary Medicines Authority (APVMA). Only 2,4-D HVE products already purchased may be used and only until 31 August 2014. See the APVMA website for more details.
Ester formulation use restrictions
In Victoria, ester formulations of 2,4-D, 2,4-DB, MCPA and triclopyr are classified as 'restricted use' chemicals and can only be legally used by individuals who hold:
- a valid Agricultural Chemical User Permit (ACUP) (or who work under the direct supervision of an ACUP holder).
- a valid Commercial Operator License
- a valid Pilot (Chemical Rating) Licence
- a valid Department of Health Licence to Use Pesticides.
In addition, the use of some ester herbicides is restricted in Agricultural Chemical Control Areas (ACCA) when they are in operation. This is to provide protection for valuable crops during their growing seasons.
Another cause of off-target damage is chemical run-off. To avoid run-off:
- decant chemicals carefully to prevent spillage
- locate chemical mixing and wash-down sites away from streams, drains and bores
- store chemicals carefully to prevent leakage
- avoid back-siphoning chemicals when filling tanks
- provide spray employee/contractors with a farm plan that outlines waterways
- observe any 'DO NOT...' statements on the label relating to spraying in wet or water-logged soils
- spray away from water when treating weeds on a bank
- establish vegetative buffers between crops and waterways
- cultivate across slopes
- use the right water rate for the soil type
- do not spray when rain is expected
- avoid over-irrigating after applying chemicals
- constantly monitor weather conditions while spraying is taking place
- ensure that application equipment is correctly calibrated.
Notification requirements for spraying near schools, hospitals, aged care services or children's services
Legislation requires certain notifications when applying agricultural chemicals by air or mister within 200 metres of a school, hospital, aged care service or children's service (e.g. kindergarten or child care centre).
At the time a person is employed or contracted to carry out agricultural spraying by aerial spraying or mister (excludes standard boom spray), the land manager must:
- advise the employee or spray contractor in writing whether there is a school, hospital, aged care service or children's service within 200 metres of the land to be sprayed, and
- provide the employee or spray contractor with details relating to the location of the school, hospital, aged care service or children's service.
The employee or spray contractor must not begin spraying without this information.
At least 24 hours before spraying is to occur within 200 metres of these facilities, the spray employee or contractor must provide the land manager with the name of the agricultural chemical product to be used and the proposed time, date and duration of the spraying.
At least 12 hours before spraying is to occur within 200 metres of these facilities, the land manager must make every reasonable effort to inform the school principal or site manager of the agricultural chemical product to be used, the location of the proposed spraying and the proposed time, date and duration of spraying.
The department has developed an agricultural spraying notification template that chemical applicators may use to notify site managers / principals of their intention to spray.
Aerial spraying in Victoria
Aerial spraying of agricultural chemicals in Victoria is regulated by both the department and the Civil Aviation Safety Authority (CASA).
If an aircraft is undertaking aerial spraying of agricultural chemicals in Victoria, the pilot must hold a Pilot (Chemical Rating) Licence and the business must hold an Agricultural Aircraft Operator Licence, both issued by the department.
All aerial vehicles that undertake aircraft operations are regulated by CASA and must be licensed by that authority.
Under the Agricultural and Veterinary Chemicals (Control of Use) Regulations 2007, one or more of the following methods must be used immediately before and during aerial spraying:
- a smoke generating device used at ground level at or near the point of spraying
- an aircraft fitted with a smoke generating device that is operating
- a windsock operating and clearly visible to the pilot at ground level at or near the point of spraying, or
- an automatic weather station located at or near the point of spraying, with information about the wind speed and direction available to the pilot.
Unmanned aerial vehicles
New technology is now available that enables unmanned aerial vehicles (UAVs) to conduct aerial spraying.
UAVs will allow chemicals to be safely and efficiently applied in areas which would otherwise be inaccessible or present an unacceptable risk.
To cater for this new technology, special licence categories under CASA and the department now exist to authorise and regulate the piloting, spraying and business operations of UAVs.
A small number of remotely piloted, small-scale helicopters (the Yamaha RMAX) are expected to be licensed by CASA and the department to conduct aerial spraying in Victoria. The licences are specific to the type of aircraft and are conditional on compliance with the current operations manual for the aircraft and company.
RMAX UAVs are owned or franchised by Yamaha Australia. They hold a maximum of 16 litres of spray mixture, operate at about three metres above the ground and travel at a maximum speed of 20 kilometres per hour. The RMAX is operated by a minimum of two people (a controller and a spotter).
The legislation governing the use of agricultural chemicals in Victoria applies to RMAX users in the same way as it applies to any other aerial spraying contractor.
If you have questions or concerns about the spraying of chemicals from any aircraft, contact 136 186. If you have any general questions or concerns about the operation of aircraft or UAVs, contact CASA - phone 131 757. For more information about CASA, visit www.casa.gov.au
- A guide to using agricultural chemicals in Victoria - ground-based spray application
- Responsible use of farm chemicals
- Agricultural spraying notification template
- Calibration and preparation of boom sprayers
- Chemical use videos: spray risk management and boom sprayer management
- Guide to estimating wind speeds - for spraying agricultural chemicals
- Top 10 spraying tips
- Changes to spray drift management requirements
- Pesticides and bees
- Volatile vapour drift risk
- Using knapsack sprayers and compression sprayers