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New herbicide-resistant weeds emerge in Australia

"We’ve been aware that resistance is out there for these species, but this is the first time that the population numbers and resistance percentages have been documented," said researcher Mechelle Owen.

By Brooks Hays

PERTH, Australia, June 9 (UPI) -- The battle to control or reign in nature is never-ending. Just when scientists believe they've corralled an agricultural pest or weed, a newly adapted variety or species regains the upper hand.

That's what researchers say is happening in Western Australia, where a number of emerging weed species are proving especially resistant to herbicides.

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Resilience to herbicides is a well-documented problem among the most common agricultural weeds -- weeds like ryegrass (Lolium rigidum) and wild radish (Raphanus raphanistrum). But a new survey suggests it is also a problem among less common, but increasingly prevalent, emerging weed species.

Scientists with the Australian Herbicide Resistance Initiative recently found that less-known weeds like brome grass (Bromus) and barley grass (Hordeum spp) are sprouting more frequently in wheat and other grain fields.

Researchers analyzed nearly 500 fields in Western Australia and found brome grass present in 37 percent. Barley grass was found growing in a quarter of the fields.

Dozens of samples of each weed were collected and tested for herbicide resistance. Of the 91 separate brome grass population identified by researchers, 12 were found to be resistant to a common herbicide. A total of 47 barley grass populations were found to be resistant, many to more than one type of herbicide.

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"We've been aware that resistance is out there for these species, but this is the first time that the population numbers and resistance percentages have been documented," AHRI senior research officer Mechelle Owen said in a press release.

Herbicide resistance demands an escalating war between chemists, farmers and nature -- a game that is both expensive and potentially detrimental to the environment.

"Its important for farmers to look at other weed control options such as cutting crops for hay, stubble burning, seed crushing, to name just a few, so they are not reliant on herbicides to combat weeds," Owen said.

Researchers in Iowa recently found that mixing herbicides, as opposed to rotating them, is more effective method for reducing herbicide resistance.

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