With harvest fast approaching there is a narrowing window for weed, pest and disease management before the season ends.
Crop topping, swathing (with or without an additional spray application) plus crop desiccation or pre-harvest spraying remain useful options for spring management.
Always check for changes to registrations and rates of applications for any chemical to be applied at this late crop stage.
Also, grain receival standards need to be adhered to when delivering grain to CBH and other grain marketing organisations.
Swathing and spraying canola
While the seed set control of weeds can be an added bonus of swathing and dessication, the timing of these operations to optimise grain yield and oil content of canola can be a challenge.
Department of Primary Industries and Regional Development (DPIRD) officer Glen Riethmuller conducted a number of experiments in Katanning and Mt Barker, from 2010-2013, on the effects of desiccation, swathing and pre-harvest spraying on annual ryegrass seed viability and canola yield and oil parameters.
He found that the viability of annual ryegrass seed can be reduced substantially by desiccation, pre-harvest spraying or swathing of canola depending on the product and timing.
For more information refer to the Protecting WA crops – pre-harvest protection webpage.
For the complete details and results from this research, refer to Glen’s 2017 Research Update paper Annual ryegrass viable seed reduced by dessication and swathing canola.
Crop topping (the late application of herbicides to prevent weed seed-set) can be used for managing herbicide resistance, as a late post-emergent salvage treatment or to control any weeds that survived or were missed in other weed management strategies.
Late weed control may also reduce grain contamination but a crop-topping application will not increase grain yield.
There are paraquat and glyphosate products (read the label) registered for crop-topping in WA but these are limited for use in pulse crops and predominantly target annual ryegrass.
For further information on best timing for weed management while limiting potential impacts on the crop refer to Crop topping pulse crops.
Early control of summer weeds
Control of summer weeds is best done when the weeds are small – particularly those weeds that may be difficult to manage as they age or when growing conditions are challenging (hot, dry and dusty).
Many of our summer weeds, like Fleabane, will germinate in late spring following rains at harvest.
Take the time during the harvest operation to identify paddocks and other areas where summer weeds are germinating and then return to these paddocks following harvest to control the seedlings.
For more information on summer weeds and their control see the Summer weeds webpage.