Post-emergent label extension trial work pays off for independent consultant
Summer grass weeds have long been a challenge in the northern grain region - a problem complicated with the emergence of glyphosate resistance and tolerance.
Rather than rely on a knockdown alone, more and more growers have adopted a pre-emergent herbicide, like Dual Gold, to tackle awnless barnyard grass, liverseed grass and feathertop Rhodes grass.
Spring showers, or the lack there off, has been a limiting factor with this in-fallow use pattern: If the rain doesn’t arrive within two weeks the residual activity can start to trail-off in zero-till situations.
“Trials conducted over many years have shown that Dual Gold can be very effective in reducing germinations of these key grass weeds, without too many crop rotation restrictions,” said Mark Congreve, Senior Consultant with ICAN.
“However agronomists and growers were telling us it was extremely difficult to get the timing of application right and to be effective Dual Gold needs to go down before the first spring germinations.
“If rainfall doesn’t occur within 7 to 10 days of application then excessive product can lost without mechanical incorporation, and if applied early in the spring then it is likely to have run out of residual activity by mid to late summer”.
Identifying these constraints led to a meeting between GRDC, Syngenta, Northern Grains Alliance (NGA) and ICAN to discuss the need for a Dual Gold label update to provide better directions for growers.
“In particular, growers were telling us that they wanted use patterns that would allow for spring applications in fallow while also extending applications later into the sorghum window,” Mark said. “There was some suggestion from overseas data that Dual Gold could be applied over the top of sorghum after crop emergence.
“Having the ability to apply a ‘top-up’ application, after the sorghum crop has emerged, would allow much greater flexibility in timing the application to suit incorporating rainfall, while also extending the length of residual control.”
Any label extension to satisfy these wishes would require extensive trials over the course of years.
With no clear idea whether a post-emergent use pattern would even be approved for sorghum, the GRDC agreed to a modest co-investment of resources for project scoping.
The trial would need to assess crop tolerance, application rates and timing to ensure residue levels were not exceeded in harvested grain.
The investment paid off. As a result of this joint development approach, Dual Gold is now able to be used with greater flexibility. Key additions to this label update include; provision for single or split applications in spring/summer fallows; the addition of feathertop Rhodes grass control in several use situations; and the ability to apply Dual Gold early post-emergent in sorghum.
“Having the ability to apply earlier in the fallow and then topping-up after emergence means that there is potentially one less spray pass required during the busy planting window,” Mark said.
“This also may lower the risk of sorghum injury, which is most likely to occur from at-planting applications, should conditions become cool and wet during crop emergence.”
Gordon Cumming, Manager Chemical Regulation with the GRDC said the outcome spoke to the strengths of the GRDC being uniquely placed to deliver real value.
“This outcome is an excellent example of GRDC working with industry to develop tools that benefit Australian growers,” he said.
“GRDC networks identified the problem and came up with potential solutions that they would like to see evaluated.
“A small co-investment from GRDC research programs then followed, which ensured that a company such as Syngenta was able to justify the completion of this label update.”