Why is pesticide input efficiency so important?
Pesticide input efficiency means delivering the correct dose of the most appropriate pesticide to the target, to maximise crop protection benefit while minimising risk of off-target impact.
Applying crop protection products is a significant expense for a farming operation, both in terms of products applied and cost of capital or contracting to complete the job. To maximise return from this investment, chemical applied needs to stay in the paddock and hit and control the intended targets. Low doses of pesticides to target species through poor application can select for resistance, contributing to evolution of resistance in target insect pest and weed populations.
Importantly effective application will minimise the risks of off-target movement of pesticides or damage. Spray drift is a whole of community issue, and everyone has a responsibility to understand their obligations in managing it and ensuring agriculture maintains its social license for ongoing access to crop protection products.
What do you need to know?
How to achieve pesticide input efficiency
Pesticide input efficiency means delivering the correct dose of the most appropriate pesticide to the target, while meeting all legal requirements and not adversely impacting people, property or the environment.
What you need to consider:
- Pre-season Planning and Communication
- Plan your crop layout to reduce risk to sensitive areas. Be prepared to leave unsprayed buffers when the label requires.
- Communicate with neighbours and spray contractors about location of sensitive areas and crops.
- Ensure operators are trained and provided information for the safe use of pesticides.
- Product Selection and Use
- In addition to efficacy against the target pest/s, product selection should also aim to limit impact on non-target species (eg bees and beneficials, sensitive crops and vegetation), and manage the resistance risk.
- All products have the potential to drift. Different products can have different volatility (likelihood that the herbicide will turn into a gas). For example
- Product selection decision also includes adjuvants and tank mix partners which can impact on both product efficacy, crop safety and risk of drift.
- Water quality is important as water is the largest component of any spray operation. Refer to manufacturers guidelines about tolerances of products to different water quality parameters as well as suitable products to treat poor quality water. Note some water quality treatments can impact on spray drift risk. Always follow label recommendations regarding water volume.
- Where possible, reduce the total amount of pesticide applied through more selective approaches. Banded sprays enable the recommended rate of the product to be placed on to an area smaller than the whole field (thereby reducing the total volume of chemical over the whole field. Optical sprayers such as Weedseeker, WEEDit and See & Spray can reduce the amount of product applied. Note it is still important that the principles of good spray application are applied.
- Only use products that are registered (or have current permit) and always follow label instructions when handling and applying chemicals,
- Weather Monitoring and Recording
- Manage the spray operation according to meteorological and environmental parameters. Always stop spraying if the weather conditions become unfavourable - it risks pesticide not getting to the target and damage to surrounding sensitive crops and vegetation.
- Always follow label directions about appropriate spray conditions.
- Continually monitor the conditions at the site of application.
- Spray when wind is steady and ideally more than 5km/h and up to 15km/h. Avoid calm, variable or gusty wind. Avoid when the wind is blowing away from sensitive areas and crops
- Temperature and humidity- Higher ambient air temperatures and lower relative humidity conditions increase evaporation rates, and volatile pesticides on soil and plant surfaces vaporise faster. when the wind is blowing away from sensitive areas and crops. Avoid spraying in temperatures above 30oC. Aim to spray when Delta T is between 2 and 10 and not greater than 12.
- DO NOT SPRAY when a Hazardous surface temperature inversion exists.
- Weather conditions need to be checked regularly during spray applications and recorded as per label and state requirements.
- Pesticide Application Equipment
- Accurately deliver the correct dose to the target. This includes correct rate, choice of band percentage, choice of application volume, mixing procedures, timing of the application (pest's life cycle, appropriate spray conditions) and spray quality (droplet size and spray coverage).
- Use the largest spray quality possible while maintaining efficacy and observing label directions for minimum and maximum droplet size. Nozzles should never be operated outside of the pressure range recommended by the manufacturer. Higher or lower than recommended pressures change the droplet spectrum and the spray pattern, affecting both the risk of drift and the efficacy of the spray application.
- Keep boom height as low as possible: It is important to set the height of the boom at the minimum practical height to achieve the correct spray pattern for the nozzles. With a 110 degree nozzle using 50cm nozzle spacing, the correct boom height is 50cm above the top of the stubble or crop canopy. Use height control systems for wider booms or reduce the spraying speed to maintain boom stability/height. An increase in boom height from 50 to 70cm above the target can increase drift fourfold.
- Avoid high travel speeds. Spraying speeds more than 16 to 18km/hr with trailing rigs and more than 20-22km/hr with self-propelled sprayers greatly increases losses due to the effects at the nozzle and the aerodynamics of the machine.
- Maintenance and hygiene: The output of each nozzle should be checked pre-season and regularly during the season. Nozzles that vary more than 10 percent from manufacturer’s specifications should be replaced. Application equipment that has been used to apply herbicides should be thoroughly decontaminated before being used to apply any product to a susceptible crop.
- Select a contract spray applicator (aerial, drone and ground) that has the appropriate training and license as required in your state.
SataCrop: locate cotton fields before spraying
Cotton Australia has partnered with Precision Crop Technologies (PCT) to deliver a new era of spray drift prevention, SataCrop.
SataCrop is a digital platform that maps all crops, not just cotton, allowing growers and applicators of all products to be better informed before spraying. The website requires growers to only map their fields once and has the ability to import field boundaries from compatible software such as PCT, SST, Farmworks, John Deere and Agworld.
Hazardous surface temperature inversions
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).
A surface temperature inversion occurs when the air temperature increases with height from the ground surface, which is the opposite of what normally happens (i.e., the temperature profile is ‘inverted’). This results in a layer of cool dense air being trapped below warmer air close to the surface. Not all surface temperature inversions are hazardous, but they must be considered as such, unless recognised instrumentation exists to identify them.
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. During a hazardous inversion, air movement is much less turbulent than during the day. Sprays applied in these conditions can become trapped in this cool air layer where there is insufficient turbulence to either deposit or disperse the suspended spray droplets. This lack of turbulence results in the transport of drift over long distances in localised laminar air flows 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.
The Grains Research and Development Corporation (GRDC) and the Cotton Research and Development Corporation (CRDC) have partnered with Goanna Ag to deliver Weather and Networked Data or WAND - a spray drift hazardous inversion system that is providing real-time weather data for growers and spray operators about the presence or absence of hazardous temperature inversions.
WAND consist of a network of Profiling Automatic Weather Stations (PAWS) across the grain and cotton regions of NSW, southern and central QLD. The PAWS have remote sensing capability and new proprietary software to provide growers and spray contractors real-time weather data updated every 10 minutes.
To access the WAND network go to www.wand.com.au
So, what should you do on your farm?
- Keep comprehensive records.
- Establish communication processes to manage safety and reduce risks.
- Give careful consideration to the selection and application of pesticides.
- Use the correct application equipment and techniques.
- Ensure chemicals are transported, handled and stored appropriately.
- Dispose of unwanted chemicals and chemical containers appropriately.
- Always follow label instructions when handling and applying chemicals, including specifications regarding spray quality, spray conditions including mandatory wind speed range, and no-spray zones/buffers.
- Ensure all staff responsible for handling and applying pesticides are qualified according to relevant state and federal requirements.
- Maintain a manifest and Safety Data Sheets for chemicals deemed to be hazardous.
- Map your cotton fields on SataCrop.
Where should you go for more information?
- GRDC Spray Application Manual
- GRDC Weather Essentials for Pesticide Application
- WEEDpak Herbicide Damage ID Guide
- Cotton Pest Management Guide
- Australian Cotton Production Manual
- Guide to keeping records of herbicide distribution (QLD Government)
- Spray Drift (NSW Government)
- Spray Drift Management (APVMA)
- Keep the spray on the weeds fact sheet
- Cotton Australia summer weed control best practice guide
- CottonInfo / CSD fact sheet: Decontaminating spray equipment
- Podcast: Grower observations on spray application
- Decontamination guide
- CottonInfo fact sheet:
- CottonInfo case study:
- WAND: provides real time guidance on hazardous inversion conditions
- SataCrop: a Cotton Australia and Precision Crop Technologies (PCT) initiative designed to highlight the location of cotton fields.
- Nufarm's spray wise decisions: provides forecasts of conditions for spraying up to 10 days in advance.
- Syngenta's weather website: provides forecasts of conditions for spraying up to 10 days in advance.
- drumMUSTER: Recyling program for agricultural chemical containers.
- Spray clock diagram: 24 hour risk profile for summer spraying