AUSTRALIA'S most comprehensive analysis of the cost of weeds in cropping systems has shown that the overall annual cost to WA grain growers is $927 million or $117 a hectare.
The Grains Research and Development Corporation (GRDC) commissioned report shows that growers are investing heavily in weed management and, despite increasing levels of herbicide resistance, in-crop weed populations are mostly being kept low.
GRDC crop protection general manager Ken Young said the industry study into the cost of weeds - including yield losses and the costs of weed management practices - had input from 600 growers, as well as agronomists, consultants, agribusiness data experts and researchers.
"Weeds present one of the largest costs to grain growers and are one of the biggest influences on the management of cropping systems," Dr Young said.
"This study is the most comprehensive review to date on the cost of weeds to Australian grain growers and the adoption of weed management and tillage practices, and will help guide future decisions on cropping systems research, development and extension."
CSIRO farming systems senior research scientist Rick Llewellyn, the lead author of the report, said that while the study identified important differences between regions and agro-ecological zones, key results at a national level included:
p The overall cost of weeds to Australian grain growers is $3.3 billion annually
p Weeds are costing Australian grain growers on average $146 per hectare in expenditure and yield losses
p Average expenditure on weed control, including herbicide and non-herbicide practices, is $113/ha
p Yield losses due to weeds amounts to 2.76 million tonnes of grain
p The most expensive weeds in terms of total yield losses are annual ryegrass, wild radish and wild oats, with brome grass being a notable major weed that is increasingly costly.
Dr Llewellyn said the costs of yield losses due to weed competition ($708m nationally) were much lower than total weed management costs ($2.6b).
"Reducing the cost of weed management is one of the grains industry's largest challenges," Dr Llewellyn said.
He said that as weed control through cultivation had declined, adoption by growers of a range of other weed management practices had increased.
"Crop-topping, double knockdown and narrow windrow burning have increased, with the latter showing rapid recent increases in some areas, particularly WA," he said.
Dr Llewellyn said WA growers were leaders in the adoption of harvest weed seed control (HWSC) practices which, when combined with other control measures, played a crucial role in reducing weed populations and weed seed banks, and minimised the impact of herbicide resistance.
"The total national cost of using HWSC practices - such as narrow windrow burning, chaff carts, the Harrington Seed Destructor and chaff tramlining - is estimated at $17m annually with $13m of this in WA," he said.
