The Swarmbot ‘Mooki’ busy at work spot-spraying weeds.
Weed detection and spot spraying in fallow is a powerful way to reduce chemical use, conserve soil moisture and run down the weed seed bank.
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Andrew and Cynthia Pursehouse and their eldest son James ‘employ’ a Swarmbot named ‘Mooki’ — fitted with a 13m RBE boom and Weed-IT Quadro sensors — as their dedicated fallow spot-spraying unit on their 5100-ha mixed farming operation in NSW.
In 2015, they began optical spot spraying using a 36m Weedseeker boom on their Miller Nitro SP to reduce their chemical use in fallow fields.
Spot spraying fallow weeds — including milk thistle, fleabane, ryegrass, windmill grass and barnyard grass — uses much less chemical per spray pass than blanket spraying, representing significant savings to their business.
James said although the 36m Weedseeker boom worked well, they frequently needed their self-propelled machine to do two jobs simultaneously.
The family investigated their options and weighed up buying a second self-propelled sprayer or an autonomous (robot) to increase their spray capacity.
“While both are expensive pieces of machinery, we saw the benefit of the robotic option as the ability to do two spray jobs simultaneously without needing to employ an extra operator,” James said.
In 2022, they ordered a robotic platform from SwarmFarm as a dedicated fallow weed spot-spraying unit, and it was deployed on their property in June 2023.
“In the 14 months between June 2023 and August 2024, the Swarmbot completed 1490 engine hours, which includes time travelling, spraying and in sleep mode,” James said.
“It has an average operating speed of 9.7 ha/hour, uses 0.8 litres/ha of diesel, and has a running cost of $4/ha.”
In comparison, their SP sprayer typically covers 50 ha/hour and uses 0.9 litres/ha of diesel when camera spraying, giving a similar running cost per hectare. It also requires a driver.
Automated spot spraying is a valuable tool in the WeedSmart toolbox, reducing herbicide resistance risk through timely application on small weeds.
James said they have made a major shift from reactive to proactive weed management, where they are now targeting smaller weeds more often using a spray rotation of three to four weeks, according to weather conditions.
“All weeds are more susceptible to herbicide when they are small. The robot removes the normal temptation to hold off spraying to wait for a few more weeds to emerge.
“The fact that the robot will return to each paddock within a few weeks means that we are continually driving down the weed seed bank by eliminating small weeds before they can establish and set seed.”
The Purshouses have implemented many of the WeedSmart Big 6 tactics to reduce their risk of herbicide resistance, including increasing their spray efficacy with the robot providing a consistent 50cm boom height and slower operating speed so the Weed-IT sensors can detect very small weeds in heavy stubble.
Since adding Mooki to the farm workforce, the self-propelled sprayer’s engine hours have been reduced, extending its effective life.
Staff time and skills have also been better utilised.
“This means all jobs are being done on time, and we don’t have to worry about the fallow weeds depleting our stored soil moisture or setting seed,” James said.
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