South Perth, Western Australia
February 3, 2006
Increasing
herbicide resistance in grass weeds will push growers to adopt
alternative strategies of weed control, especially in lupin
crops.
Department of
Agriculture,
Western Australia
research officer Bob French said greater levels of herbicide
resistance, particularly in annual ryegrass, and a tendency to
sow lupin crops in wider rows, mean’t growers needed to
investigate different weed control strategies.
Herbicide resistance will be a major topic at the
Department’s Agribusiness Crop Updates, supported by the Grains
Research and Development Corporation, and at the Merredin Crop
Updates on 20 February and in Northam on 23 February.
“Greater levels of herbicide resistance means
that weeds cannot be so easily, or cheaply, controlled,” Dr
French said.
“This can result in a reduction on return from
the lupin phase in crop rotations. More importantly, it also
increases the likelihood of weed build up in the lupin phase
which can carry over to the cereal phases of the rotation.”
Dr French said in the 1980s, lupins were highly
valued because grass weeds could be more effectively controlled
with herbicides than in other crops, which resulted in weed-free
cereals.
“To maintain sustainable lupin rotations, growers
will need to look at weed control strategies which are not as
dependant on selective herbicides, including ways of making
lupins more competitive against weeds,” he said.
Dr French said sowing lupins in 50 to 75 cm rows
instead of the traditional 18 to 25 cm rows had a number of
benefits, including limiting the risk of very poor yields in dry
seasons.
However, he said weed control may not be as
effective in wide rows compared with narrow rows unless extra
measures were taken, such as spraying the inter-row area with
non-selective herbicide.
“Crops in wide rows take longer to achieve full
canopy cover than crops in narrow rows and do not compete as
well with weeds,” he said.
“In dry environments, where wide rows have
greatest yield benefit, they may never achieve full canopy cover
and offer little competition against weeds.”
Dr French said
other research funded by the GRDC showed that low densities also
reduced crop competition against weeds.
”It is
recommended that lupins be sown at rates of 40 or more plants
per square metre to compete adequately against weeds, especially
annual ryegrass,” Dr French said.
Information on herbicide resistance and lupin
sowing rates is available in ‘Herbicide
registrations The Paddock Spray Guide DAWA Bulletin 4545’.
For more information on dates and venues for
Regional Crop Updates visit
www.agric.wa.gov.au/cropupdates |