THE Department of Primary Industries and Regional Development (DPIRD) has warned that weed management will be crucial this spring, with many growers facing difficult decisions on how best to optimise paddock potential.
Variable growing season rainfall has led to growers across the agricultural region applying a range of strategies to balance weed control against costs, the risks of soil erosion and herbicide resistance and livestock feed requirements.
DPIRD research officer David Ferris said growers would have to tailor their integrated weed management plans paddock-by-paddock this year.
Dr Ferris said it was important to consider each paddock’s potential, as well as its break-even point when deciding on weed control strategies to reduce the risk of seed set impacting on future crops.
“Growers in the parts of the central, Great Southern and south coast areas that have received good growing season rainfall will be in a position to undertake weed control to maximise yields and prevent future seed set,” Dr Ferris said.
“However, growers further north and east may need to evaluate each crop’s potential and how much they can afford to spend on weed control to determine the best strategy.”
Dr Ferris said there was a range of weed control strategies that could be employed and urged growers to consider the short and long term implications of each strategy when making paddock management decisions.
“The underlying driver for spring weed control is to prevent additions to the weed seed bank that will impact on crop performance in subsequent years,” he said.
“Growers will need to factor in the potential feed value, herbicide resistance, the cost of harvesting and likely grain and livestock prices when deciding which strategy to adopt.
“They should also try to avoid a situation where weed seed set blows out and weed control becomes a crop constraint for the next five years or so.”
Another imperative is to retain enough ground cover to prevent wind erosion, while crop topping will be another challenge for some growers.
“Timing is crucial for both these situations, delaying herbicide applications until just before the weeds set viable seed,” Dr Ferris said.
“This will help to maximise weed biomass cover in failed crops and help to minimise the impact of herbicides on harvestable crops.
“Although this isn’t the scenario growers had hoped for, it does provide an opportunity to clean up weedy paddocks and set them up for next year.”
There are also opportunities to minimise the replenishment of weed seed banks at harvest, even if weeds have not been sprayed and set seed.
“One option to minimise ‘seed rain’ is to use chaff lining or to run a chaff cart behind the header, from which the contents can be used to provide valuable feed for livestock,” Dr Ferris said.
Growers are reminded to be aware of recent changes to label requirements and to strictly adhere to Maximum Residue Limits and withholding periods.
More tactical information on weed management is available on DPIRD’s 2017 Growing Season Resources webpage or in the Protecting WA Crops newsletter, both found at agric.wa.gov.au
