Waging war on weeds: the latest research

laser weed control
Blasting a weed with a laser, leaving it smoking with a high voltage zap or watching it wither under a giant magnifying glass may well be my cathartic farm job of the future.

Waging war on weeds – whether with chemicals or tillage – is set to get a whole lot smarter, more cost-effective and kinder for the environment, thanks to new work at the University of Sydney.

I was delighted when researcher Michael Walsh agreed to give Milk Maid Marian a sneak peek at the direction of his team’s research.

MMM: Farmers traditionally use chemicals or tillage to control weeds. Why should we consider new forms of weed control?

MW: Like many other decisions on farm, cost is the driving factor behind the need to consider other forms of weed control. Herbicides and tillage are both relatively cheap to apply but there are production risks to the use of these treatments.

There is a risk of herbicide resistance that occurs every time a herbicide is applied and once resistance evolves it remains in a weed population forever and therefore the herbicide is no longer useful.

For tillage it is the risk associated with soil disturbance and the lack of selectivity. In a pasture tillage for weed control will result in the loss of grazing for that paddock.

MMM: What are the alternatives being researched at the University of Sydney?
MW: We have been evaluating targeted tillage and more recently laser weeding, but we are also keen to investigate electrical weeding and solar weeding.

Electrical weeding is simply just using electricity to “shock” weeds. A weed is touched with a positive terminal and the earth acts as the ground so the charge passes through the weed burning cells as it goes. In the UK there are commercially available hand held electrical weeders.

Solar weed control

Solar weeding is using the sun to burn weeds. It’s the magnifying glass approach where a lens (grooved plastic sheet) is used to concentrate sunlight on to a weed to burn it. These types of lenses (Fresnel lens) are used in lighthouses to focus light into a strong beam.

MMM: What are the benefits?
MW: Initially the main benefit will be the reduced reliance on herbicides.

There will be substantial savings in weed control costs associated with controlling individual weeds rather than applying a blanket weed control treatment to the whole field. These savings will depend on weed density and it is hope that with good weed identification systems we will be better able to reduce weeds to very low numbers in crop and pasture paddocks.

MMM: Other forms of automated weed control have struggled to identify weeds in pasture. How can this be overcome?
MW: The development of new camera and sensing technologies for cars and phones has created the opportunity for weed recognition and identification. This will allow us to use tillage and other physical weed control tactics to selectively target weeds in crop and pasture situations.

MMM: What needs to happen to make this technology a reality on Australian dairy farms?
MW: I guess the first thing to do is to start working on systems that are able to identify weeds in pastures. Basically it is just a matter of training a sensing system (e.g. a robot) to recognise what is a weed and what is pasture plant. This is typically achieved by building up a library of weed images as they occur in pastures over the growing season.

Thank you very much, Michael, for this glimpse of what farmers can look forward to in the war on weeds! I do hope the dairy community is quick to support such an exciting development for farmers and the planet and can begin building that library of weeds.

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