Effective spray application can save growers time, money and resources – and better protect the environment.
But how best to spray?
Andrew Hewitt and a team from the University of Queensland have been developing an innovative new spraying system, which is due to finish its trials in May next year.
In this article, Andrew provides his top tips for growers for this coming spraying season.
Calibrate your sprayer
Even the best sprayer can do a lousy job if not optimally set up, says Andrew. Assess coverage using water sensitive papers throughout the canopy, or use fluorescent dyes and check coverage with a UV light, or simply use a coloured spray mix and hang white paper in the canopy. If coverage is not good or uniform, then adjust the sprayer, water volume rate and driving speed and repeat.
Target the canopy
Only target the canopy and one row per spray pass. ‘Don't have the spray go over the top of the canopy, or through several rows. That just wastes chemical.'
Spray on time
Timing is everything with most pests. Scout regularly for pests and diseases and if you find them, time your spraying accordingly.
Check the weather
Always check weather forecasts when spraying to avoid rain events soon afterwards; spray losses through drift if high winds are forecast (above 15 km/ h); or temperature inversion issues when there is little or no wind.
Use the right nozzle and pressure for the job
Highest coverage may be with finer sprays, but drift is lowest with coarser sprays, says Andrew. ‘For example, herbicide work should be as coarse as possible for good coverage.’
Consider new spraying systems if your sprayers are old. ‘Recaptured and recycled sprayers did among the best in our studies’, said Andrew.
Consider sensor and precision spraying systems
‘We are getting excellent results with drones in our current work and with sensors for canopies. The Wine Australia-funded app Viticanopy can assess the leaf area index and support your sprayer calibration water volume rate.’
Adjuvants can help with droplet spreading, sticking and uptake – particularly when cutting water rates. ‘We have not seen conclusive results yet showing their help with drift management, so it is still essential to manage drift using the well proven ways: avoiding adverse weather, correctly targeting only the canopy with the row being sprayed, watching wind direction and speed relative to any non-target sensitive areas and setting up the sprayer and nozzles correctly.’