Old-school method for radish

Old-school style hand weeding of wild radish could be cheaper than spraying in paddocks where plants are in low densities, according to Australian Herbicide Resistance Initiative Leader Peter Newman.

Speaking at last week’s Grains Research Updates, Mr Newman said wild radish in the northern cropping region of WA was extremely resistant, but in most cases the crops were now very clean.

“Most growers have targeted the radish seed bank for a decade or more through crop and herbicide rotation, robust herbicide mixes, narrow windrow burning, and the attitude that wild radish should never be allowed to set seed,” he said.

As a result, many growers are saying the same thing, that their radish numbers are low, but the remaining few cost a fortune to control.

Mr Newman said with all-terrain vehicles and a full work day, teams of two or three people could hand weed 100 to 150ha a day at a cost of $2.50 to $4/ha, if the wild radish density was 5-10 plants a hectare or less.

His findings came following a GRDC-funded one-year study through the Geraldton RCSN, which aimed to determine how to assess which paddocks were candidates for hand weeding, and whether it was economically viable.

“Hand weeding is a viable option for paddocks with very low weed densities. It may even be an option to spray paddocks with moderate densities of radish with cheap herbicides, and then hand weed the survivors,” he said.

Mr Newman said 2015 growing conditions were ideal for low radish numbers in crops near Geraldton.

Abundant summer rains provided a good knockdown and early seeding opportunities, followed by dry conditions in May, which limited the radish germination in crops.

“When wheat crops were at the 2-3 leaf stage, growers did what they do every year; drive over the crop and plan their post-emergent wild radish spray. But this year was different — many farmers could scarcely find a wild radish plant,” he said.

“Some paddocks were simply not worth spraying, but growers were scared not to spray; they had spent a decade getting their seed bank down and they didn’t want to undo their hard work.”

Mr Newman said if deciding whether to take this approach, the first step was to assess tillering wheat crops by driving down a spray tramline with a person either side of the vehicle looking out of the window.

If the paddock was considered to have low density of radish weeds, the next step was to source readily-available backpacker labour, at a cost of around around $25 an hour.

Supplied also with a vehicle, hat, long sleeves, gloves and plenty of sunscreen, water and insect repellent, teams of three worked together with a driver and two pickers.

These teams would drive down boomspray tramlines and walk into the crop from there to remove radish, Mr Newman said.