Australia
May 5, 2014
Research into wild radish control through the Wimmera and Mallee regions suggests growers should adopt new chemical modes of action into their broadleaf weed management programs that offer much better control than currently used herbicides.
Birchip Cropping Group Research Manager and Agronomist Simon Craig said the research results were more of a “heads up’’ than a warning to growers, but he was surprised how some paddocks with both wild radish and annual ryegrass problems could be in production.
“The research indicates growers should be paying more attention to broadleaf weeds,’’ Simon said.
“Radish problems are generally localised to the higher rainfall, sandier areas, but Indian hedge mustard and turnip are everywhere and there are also significant populations of bifora, fumitory and prickly lettuce.’’
The research, conducted last season and funded by GRDC, involved a survey of 20 paddocks in two higher rainfall areas where radish persists on sandier, lower pH soils, including around Corack, Jeffcott and Charlton and also Nhill, Dimboola, Jeparit and Hopetoun, as well as at Pira, north-west of Swan Hill.
The survey comprised demonstration trials of 12 different post-emergent herbicides applied at recommended rates, as well as a control treatment, in each paddock.
At a larger, replicated site near Corack, herbicides were applied at three different timings, including 2-leaf, 5-leaf and Z30 crop growth stages, while applications at other sites were performed at the 2-leaf and 6-leaf stages.
Simon said plant counts were taken within plots at time of spraying and then at 28 and 54 days after applications.
He said growers attended the sites three weeks after application to visually assess the control provided by the different herbicides, while numerous agronomist/grower groups also visited the trials during the season.
“There were continual germinations of radish and populations in most treatments were controlled by all herbicide groups, suggesting no resistance, however control from Group B and I herbicides was weaker.’’
“At Corack, where we had the three application timings, products like Brodal®, Eclipse® and Tigrex® fell down in their level of control, whereas products like Velocity® and Precept® consistently achieved the best control over all three treatment times.
“The 2,4-D Amine/Ester, Eclipse and 2,4-D Ester/Eclipse performed poorly, while Precept and Velocity provided much better weed control than those products.’’
Precept and Velocity post-emergent herbicides, both from Bayer, are based on the company’s novel active ingredient, pyrasulfotole.
Pyrasulfotole interrupts three biological processes crucial to weed growth. It stops their ability to generate an adequate supply of energy and produce vitamin E and it prevents carotenoid production. This leaves the chlorophyll molecules unprotected against dangerous ultra-violet rays and excess light. Sunlight therefore destroys the chlorophyll and the weeds turn white and die.
“Velocity provides very quick brown-out. Precept takes longer, but it provides good control at the end,’’ Simon said.
He said the research showed growers that some chemicals were breaking down and so they should incorporate new modes of action into their broadleaf weed control rotations.
“Group I and B herbicides by themselves are giving quite poor control and applying them late, at 3 to 5-leaf, reduces later spray options.’’
“They should be going with products like Velocity and Precept early and then with 2,4-D amine and Eclipse for a later clean-up, or go with Velocity early and have Precept as a later option.’’
Simon said growers could also consider broadleaf control options with other crops like Roundup Ready® or triazine-tolerant canola.
ENDS
Velocity®, Eclipse®, Tigrex®, Brodal® and Precept® are registered trademarks of the Bayer Group.
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