Cooked: no comeback for microwaved weeds

A photo of a bearded man

Dr Graham Brodie working on his prototype microwave
weed killer.

 PHOTO: Paul Jones

The prototype of a microwave weed-killing technology has provided proof of concept and there is opportunity to develop it further
 

The same microwaves that can be used to heat a meal can also be used to kill weeds. Heating the water in a plant’s cells turns the water to steam, causing the cells to explode.

Field trials in 2012 show that it takes less than a second for microwaves to kill an entire plant.

Dr Graham Brodie from the University of Melbourne has developed the technology, using microwave horn antennae mounted on a trailer. The antennae focus the microwaves at ground level.

The prototype has a two-metre span and was trialled on fleabane, prickly paddy melon and marshmallow weed at the University of Melbourne’s Dookie campus in northern Victoria. It was also tested on ryegrass seeds and annual and perennial ryegrass.

Dr Brodie says microwaves offer a potential alternative to herbicides in areas where weeds have developed herbicide resistance or residual weed seeds are a problem.

He says the ryegrass seedbank is one issue in particular he hopes to address with the microwave technology. Although it is feasible to kill seeds in the soil, it is at the moment too energy intensive to be practical. In the Dookie field trials the microwaves had to be applied for five to 10 seconds to kill ryegrass seeds in the soil. Even so, Dr Brodie says the technology might still prove handy for highly resistant and intractable seedbanks.

The potential advantages of microwaves are that they generally kill weeds immediately and there are no residues, so potentially restrictive withholding periods for crops would not apply.

The development and testing of the microwave prototype was funded by the Rural Industries Research and Development Corporation as part of the Australian Government’s National Weeds and Productivity Research Program.

More information:

Dr Graham Brodie
03 5833 9273
grahamb@unimelb.edu.au

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