Need for rotations to control brome

RYEGRASS is popularly regarded as Australian croppers’ public enemy number one, however in the low rainfall zones of SA, Victoria and NSW there is increasing evidence that brome grass is proving to be a bigger problem.
Nanjing Night Net

The purple-hued grass is thriving, in particular in no-till systems, and is more difficult to control than ryegrass due to a lack of herbicide options.

Sam Kleemann, of the University of Adelaide, which is conducting work on the grass, said one of the major steps to lessening the hold of brome grass was to mix up crop rotations.

“Seeing the increase of canola and pulses over the last couple of years has been good, in particular when you get two years of control, which can really cut down on the seedbank,” he said, speaking at a Mallee Sustainable Farming (MSFP) field day at Ouyen recently.

He said that because most selective herbicides targeted ryegrass, there wasn’t a lot particularly effective for brome.

However, Clearfield technology, which makes use of the ‘imi’ group of herbicides, can be effective, so Dr Kleemann said farmers needed to consider the option of a Clearfield phase if they wished to continue growing cereal on cereal.

The news of the expected introduction of the Sakura grass herbicide will not make much different in terms of brome control.

“Sakura is very good for ryegrass, but it is unlikely to even be registered for brome,” Dr Kleemann said.

Meanwhile, he said Group B sulfonylurea herbicides, such as Glean, Logran and Ally were subject to resistance.

Brome is also adapting to cropping systems in its germination.

He said the reproductive behaviour of the crop had changed, due to chemical control of the crop in the past.

More brome grass remains dormant after the first rain now, which means less is controlled by a pre-emergent control than in the past.

“It now seems to require a colder period to germinate, which means it is hard to get good control with a pre-emergent herbicide.”

He said a two year break at least was preferable, as there could still be 30pc of viable seed after a year off.

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