Herbicide resistance is a growing problem for Australia's croplands, and the only way to halt its spread is to adopt a wider range of weed control measures, an expert says. Listen Duration: 3 minutes 48 seconds 3 m 48 s Listen Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. The Australian Herbicide Resistance Initiative's Peter Newman discusses strategies for keeping herbicide resistance weeds at bay ( Clint Jasper ) Download 1.7 MB

Years of continuous cropping, with a heavy reliance on just a few types of herbicide have seen common weeds like ryegrass and wild radish become immune to its mode of action, and difficult to control.

Western Australia's wheatbelt was one of the first regions to report major herbicide resistance problems.

But the Australian Herbicide Resistance Initiative's Peter Newman said as cultural practises of WA farmers change, they're become more successful at lowering the total amount of weed seeds in the crop.

He said despite these practises being common knowledge, the problem was growing across the country.

"A number of surveys, conducted over time are showing as herbicide use increases with more continuous cropping, resistance is getting worse," he said.

Mr Newman recommended 'stacking' five different control methods in order to tackle the weed seed bank. Chaff carts prevent weed seeds from returning to the soil, lowering the paddocks seed bank. ( Clint Jasper )

These include the double knock technique, where crops are sprayed with glyphosate, followed by another herbicide soon after, the mixing and rotating of herbicides, reducing crop competition with weeds by reducing the space between rows, stopping seed set and mechanical removal of seeds with chaff carts or windrow burning.

None of these are new techniques, many are free or relatively inexpensive, and their benefits have been touted at field days and crop updates for years.

But Mr Newman said just like the messages people recieve about their health, farmers are sometimes slow to change the way they farm.

Rural news in your inbox? Subscribe for the national headlines of the day.

"It's much harder to adopt these practises than to simply just spray herbicides," he said.

"Farmers are constantly being told what they should be doing or changing, and this is just one issue on their plate.

"It's a slow turning wheel, but farmers eventually reach the point where they are fed up, and once their attitude shifts and they adopt these practises, they start having a win."

Free controls

Mr Newman said the space left between rows of crops and the direction crops are sown in are two free ways to help reduce weeds in crops.

In a paper published in the latest edition of the journal Weed Research, colleagues from the Australian Herbicide Resistance Initiative revealed planting in an east to west crop direction consistently reduced the amount of sunlight available to annual ryegrass, when compared with a north-south orientation.

In trials across the WA wheatbelt, the researchers reported planting in an east-west direction meant the 'photosynthetically active radiation' available to the ryegrass weed seeds was reduced, and crops became more competitive as a result.