Alison MacGregor has been giving grape growers across the Sunraysia a bit of a spray lately.
And it’s necessary, according to the Australian Table Grape Association extension project and team lead, to help the industry move into the next generation.
With 30 years of research and field experience behind her, Ms MacGregor knows a thing or two about sprays. She says there are four key factors to growers getting it right when it comes to getting the right volume of spray on their vines and fruit.
1. Where to get droplets, such as canopy, under leaves, on fruit, shoot tips etc.
2. Optimal setup: Size of droplets and air direction, volume, speed.
3. How do you measure and assess the performance of the spraying?
4. When you have all that data, how do you effectively interpret it?
With an extensive wine and dried fruit background, her transition to table grapes has enabled Ms MacGregor and the industry to collaborate with Australian Wine Research Institute and apply that to table grapes.
“Table grapes present a different canopy challenge and their growers are judged on the appearance of their fruit; the perfect bunch is where the money is,” she said.
“In today’s market, the starting point in any disease or pest control program is to minimise treatment and stay well within any chemical residue thresholds to remain domestically and globally competitive.
“In other words, when it comes to spraying, if you can do it properly you have given yourself the best possible chance at getting the best possible result.”
The current program has seen five grower workshops completed, with two to go. Ms MacGregor said that has taken participants through strategies about how to optimise delivery for every stage of the growth process, which each present a different challenge and courses are tailored to suit the area where they are delivered.
She said once a grower decides the priority targets – such as the underside of leaves or bunches before they flower – you have to get sprayers set up to deliver the best possible.
In a season such as 2022 and its conditions, growers are going to be really challenged by powdery and downy mildew, phomopsis, black spot and botrytis.
Set-up for these includes configuring the nozzles, setting up the air speed and direction, matching it to the speed of your sprayer and then the distance to canopies.
“You go through that whole process – nozzles, droplets, air, machinery – but in the end how do you really know it worked, and how do you assess the outcome?” she said.
“You monitor the coverage but when you look at those results, how do we interpret them accurately?”
“One way, which was demonstrated at the workshops, is to use water sensitive, powder-coated cards.
“As soon as they are hit by a droplet it cuts through the coating and turns the yellow card blue.
It doesn’t have to be an expensive, or labour intensive, exercise. If you get just 10 cards, fold them over for 20 surfaces, then put five of them inside the canopy and five outside, drive past for a spray run and you will pretty quickly get a clear picture of how even the coverage is.
“And there is still the other question – how much is enough?”
This is where, Ms MacGregor said, those four core points she outlined above, “give you the power to set up your spraying program for the best result”.
She said there are specific places in the canopy or vine where the target changes, or different targets are dictated by different canopy architecture.
This means you need to reassess each time you set out to spray. Over time your background knowledge will develop and you will get a clearer picture of the best set up for each growth stage.
“This makes spraying much more efficient. Getting this right will pay off big time in the long run,” she added.
“As an industry we are now on the cusp of being able to access to some quite sophisticated technology, with, for example, nozzles that turn on when there is canopy and off when there are gaps.
“Spraying machinery in the viticulture and horticulture industries has evolved significantly in the past 20 years and we have the opportunity to use much better delivery systems.
“I believe just about any sprayer can do a good job if you take the time to set it up properly.”
