Applying crop protection products is one of the biggest expenses in a farming operation, both in terms of chemical products and capital investment in fit-for-purpose equipment to do the job.
To maximise return from this investment, chemical applied needs to stay in the paddock and hit the intended targets.
Effective application will minimise the risks of off-target damage.
Spray Drift is a whole of community issue, and everyone has a responsibility to understand their obligations in managing it.
We have developed this resource to help growers and spray operators follow best practice application techniques in accordance with the most up-to-date research and information.
We also have a role in:
Investing in fundamental research to help define safe, efficacious and efficient spray practices
Supporting the development of resources to communicate this research and best practice
Supporting on-going training for spray applicators
Liaising with industry to ensure consistent messaging and approach.
Pesticide applications during hazardous surface temperature inversions can lead to spray drift causing severe damage up to several kilometres off target. Current regulations prohibit spraying of agricultural chemicals when hazardous temperature inversions exist.
Hazardous inversions have only recently been defined and methods to detect and forecast them specified (Grace and Tepper 2021).
During a hazardous inversion, very weak turbulence supports the transport of drift over long distances and widespread deposition at high concentrations. When a hazardous inversion has established, it acts like a barrier, isolating the inversion layer from the normal weather situation, especially the normal wind speed and direction.
In the cool and dense air of hazardous inversions, drift can be captured in laminar winds that glide smoothly down slopes, deviate around obstacles, flow parallel to contours and generally flow towards low-lying areas where they converge and concentrate; all the while transporting airborne material such as spray drift.
How to avoid hazardous inversions
Not all inversions are hazardous, but they must be considered as such, unless recognised instrumentation exists to identify them.
There really are only two ways to avoid hazardous inversions:
only spray from one-and-a-half hours after sunrise, and up to one hour before sunset; or
operate in accordance with advice issued by a recognised inversion monitoring weather system.
When application occurs in an area not covered by recognised inversion monitoring weather stations, all the surface temperature inversion conditions are regarded as hazardous. (Australian Pesticide and Veterinary Medicines Authority (APVMA))
Hazardous inversions are best monitored by networks of observation towers detecting the intensity of turbulence in the atmosphere, along with the vertical temperature difference.
Precautions for night spraying
CRITICAL – select spray quality and spray practices to eliminate droplets less than 150μm.
Avoid spraying when winds are less than 11km/h between sunset and up to 1.5 hours* after sunrise.
Select operating speeds not conducive to the lifting of spray particles behind the machine.
Keep boom height low to limit atmospheric exposure and influence on droplets.
Do not spray when mist or fog are evident and/or Delta T is less than 2.
Use wind meters, flags or smoke devices for wind flow and stability reference.
Utilise a recognised inversion monitoring system that provides real-time weather data to growers and spray operators about the presence of temperature inversions.
*1.5 hours is a precaution to limit the possibility of pesticides being lifted by thermals into the eroding and overhead inversion where they may concentrate and be transported in unpredictable directions due to wind shear.
The Australian Pesticides and Veterinary Medicines Authority (APVMA) finalised the review of all 2,4-D products in September 2020. This resulted in several amendments and changes to all labels relating to the herbicide’s conditions of use.
The new instructions for use include:
a mandatory requirement to use nozzles producing droplets no smaller than very coarse spray quality;
an advisory statement about spray application over summer to use extremely coarse (XC) to ultra-coarse (UC) spray quality in sensitive areas;
DO NOT spray when hazardous surface temperature inversion conditions exist;
DO NOT apply if heavy rains or storms are forecast within three days, or if any rain is expected within six hours; and
DO NOT apply in a manner that may cause an unacceptable impact to native vegetation, agricultural crops, landscaped gardens and aquaculture production, or cause contamination of plant or livestock commodities, outside the application site from spray drift.
Increased record keeping requirements including; temperature, relative humidity, Delta T, wind speed, is there a temperature inversion
More-detailed buffer zones are now provided on the label for boomsprays, optical spot spraying technology and aircraft, taking into account application rate and release height.
Videos
Watch the five-part Spray Application Series developed by spray consultant Bill Gordon to help explain spray operations and the practical steps required for working with 2,4-D under the new label requirements.
Experienced Queensland spray contractor Russell Fuhlbohm talking to spray specialist Bill Gordon about minimising spray drift and nozzle selection since the changes to 2,4-D labels and permits.
Spray specialist Bill Gordon discussing the impact of weather conditions, particularly inversion layers, on spray application especially given the changes to 2, 4-D labels and permits.
When your cereal paddocks are surrounded by horticultural tree and vine crops and the residential sprawl is encroaching the farm's boundaries, how do you manage your spray program to minimise drift?.
The Australian Pesticides and Veterinary Medicines Authority (APVMA) is the regulator of agricultural and veterinary (agvet) chemical products in Australia. For an agvet chemical product to legally be manufactured, imported, supplied, sold or used in Australia, it must be registered by the APVMA.
The APVMA regulates agvet products up to—and including—the point of retail sale. For a full list of registered agvet products refer to https://portal.apvma.gov.au/pubcris.
From the point of sale, each state or territory controls how the use of agvet products are enforced within their own jurisdictions.
Applying crop protection products is one of the biggest expenses in a farming operation, both in terms of chemical products and capital investment in fit-for-purpose equipment to do the job.