Brendon Cant brendon at iinet.net.au
Wed Nov 30 10:37:12 EST 2005


Annual ryegrass and wild radish, the two most problematic weeds of WA crop
production systems, cause substantial yield losses and have a remarkable
ability to establish large, persistent seedbanks.

In the face of continuing evolution of herbicide resistance, with WA now
having more multiple resistant than susceptible populations, the Grains
Research and Development Corporation has recognised the urgent need to
investigate non-herbicidal weed control strategies.

Collaborating with Peter Newman of the Department of Agriculture, Michael
Walsh of the WA Herbicide Resistance Initiative found that burning windrows
effectively targeted annual ryegrass and wild radish seed, preventing them
entering the seedbank and causing problems during subsequent cropping

Using a kiln at predetermined temperatures and for short durations, Dr Walsh
determined that 400° C was required to kill annual ryegrass seed following
10 seconds of exposure and 500o C for the same duration was needed for
complete wild radish seed kill.

Narrow windrow burning was more effective than standing stubble burning at
destroying annual ryegrass seeds and reducing subsequent emergence of annual
ryegrass seedlings at the start of the growing season.

Ryegrass seedling counts revealed about 99 per cent of ryegrass seed placed
in the windrow at harvest was destroyed by the burning, while in the stubble
treatment about 80 per cent of the ryegrass seed was destroyed.

Therefore, although the burn was not hot enough for long enough to give a
total seed kill there was a substantial proportion of the ryegrass seed
killed by stubble burning.

Similar results were found when burning narrow windrows of lupin and wheat
stubbles to destroy wild radish seed.

To maximise the potential for weed seed destruction, Dr Walsh recommended
burning narrow windrows early in the burning season and during the warmest
part of the day, in order to achieve the hottest burn possible.


The Crop Doctor is GRDC Managing Director, Peter Reading, Tel 02 6272 5525
Further Information: Dr Michael Walsh, Tel 08 6488 7872
GRDC REF:UWA399/CDjune051/Sandow

Brendon Cant & Associates
Public Relations & Marketing
114 Branksome Gardens
City Beach WA 6015
Tel 08 9385 7779
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