Bill Campbell presents a GRDC advanced spray application workshop to growers in Ravensthorpe, WA.
Growers should be aware of factors that affect spraying outcomes in order to implement the optimal sprayer set-up
Farmanco consultant Bill Campbell, who delivers GRDC advanced spray application workshops, says the trick is to balance efficacy while minimising spray drift.
“There are some simple ways that growers can optimise their spray efficacy. Once those settings have been selected, they can then consider all the other factors that affect drift,” Mr Campbell says.
“The key to getting the best spray outcome is to know your target and the mode of action you are using,” he says. “There are three standard configurations you may need to use throughout the year. If spraying broadleaf weeds in a low canopy, or summer fallow spraying, then generally lower water volumes and a coarser spray quality are required.
“Knockdowns, grass selectives and insecticides all require higher water rates with medium-to-coarse spray quality to get good coverage on the smaller targets. Fungicides are applied later in the growing season where the canopy is larger, which means they need very high water rates, “ Mr Campbell says.
Spray guidelines have provided quantitative targets that growers should aim to achieve:
summer/broadleaf sprays require 20 to 30 drops per square centimetre, with nine to 10 per cent of the area covered;
good coverage situations, such as knockdowns, grass selectives and insecticides, require 40 drops/cm2, with 12 to 15 per cent of the area covered; and
excellent coverage situations, such as fungicides, require 70 drops/cm2, with 40 per cent of the area covered.
However, Mr Campbell says that there are general set-up rules for water volume and spray quality that can be applied to make the task easier.
“If growers use these settings, they will almost always achieve the guidelines for optimal spray efficacy. If for any reason someone wants to stray from these rules of thumb, growers can directly check their set-up using water-sensitive paper with the GRDC-funded app ‘SnapCard’,” he says.
Easy spray set-up guide
General guidelines for different targets to achieve minimum coverage requirements with different modes of action (MoA).
- Fallow/broadleaf weeds (translocated MoA): 50 to 60 litres of water per hectare with a coarse to very coarse spray quality.
- Knockdowns/grass weeds/insecticides: minimum 75L/ha water, medium-to-coarse spray quality.
- Fungicides: 100L/ha water, medium spray quality.
There is a wide range of factors that growers need to consider before spraying to minimise drift.
“Weather conditions, nozzle design, spray quality and water volume, product and adjuvant, spray height, speed and the boom set-up all affect the chance of spray drift,” Mr Campbell says.
“These can be grouped into a few different types of variables. There are those that will have been selected to optimise efficacy (spray quality, water volume and product), those that may or may not be able to be adjusted (adjacent crops and spray conditions), those that growers can adjust (nozzle type and operating pressures, adjuvant, spray height and speed) and, of course, the weather.”
Weather impacts on spraying are complicated. However, a recent change to product labelling requirements makes it easier for growers, as most products reviewed by the Australian Pesticides and Veterinary Medicines Authority now have mandatory conditions listed on the label, specifying the weather conditions in which the product can and cannot be sprayed. The labels also now have mandatory buffer zones for the protection of human health, environmental safety and terms of trade.
Growers also need to be aware of the different state requirements for specific products, such as phenoxy ester formulations, and restricted spray zones around sensitive crops
The GRDC has several fact sheets and publications to help growers choose the best spray settings to minimise spray drift.
0427 545 553,
Test your mites for resistance
Benefits flow from on-farm storage in the Mallee
GRDC Project Code