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War on weeds won at harvest

Controlling weed seeds at harvest is the best strategy to prolong the life of herbicides threatened by resistant weed populations.

Michael Walsh, of the Australian Herbicide Resistance Initiative, said harvest weed seed control played an important supporting role to other strategies that focused on early season weed control.

Michael Walsh in wheat paddock

Battleground: Michael Walsh in a wheat paddock, with a Destructor in the background

“If there is one message we want to deliver, it is to control weed seeds at harvest – whether that is using the Harrington Seed Destructor or a chaff cart behind your header, baling harvest residues, or narrow windrow burning, the key is to capture and destroy seeds from weeds,” Dr Walsh said.

The Harrington Seed Destructor, built by De Bruin Engineering in South Australia, has been entered in the Australian Machine of the Year Award at this year’s Elmore Field Days.

Research supported by the Grains Research and Development Corporation shows seedbanks of annual weeds can be rapidly depleted when weed seed control systems are used to capture or destroy weed seeds at harvest.

“Our weed control efforts are aimed at driving these seedbanks towards zero,” Dr Walsh said.

“Harvest weed seed control systems play an important role in that they are the last opportunity during the cropping season to attack weeds by preventing seedbank inputs. The key is: control the seedbank to control the weed.”

Dr Walsh said annual weeds such as ryegrass, wild radish, brome grass and wild oats had adapted to cropping systems, growing to similar heights as cereals and maturing at the same time as annual crops.

“For this reason, some growers may be sceptical about how much seed is captured at harvest, but AHRI research shows a very high percentage of total weed seed production is retained on plants at a height that ensures collection during the harvest operation.

“However, the best time to target these weed species is at the start of harvest as weed seed shedding occurs over the harvest period, reducing the amount of seed that can be collected and subsequently destroyed.”

Research showed that at the start of harvest high proportions of weed seeds were retained at least 15cm above the soil surface.

By harvesting at this height weed seeds were captured by the header.

Read the original article here.

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