![New gene-stack technology in Australian cotton varieties gives growers the ability to manage summer weeds without compromising glyphosate's "armour". New gene-stack technology in Australian cotton varieties gives growers the ability to manage summer weeds without compromising glyphosate's "armour".](/images/transform/v1/crop/frm/PcEc42cje6pcPmWfEZHiNS/bacdb468-e3a2-46a6-ac5a-5b13826f51e8.JPG/r0_134_4032_2643_w1200_h678_fmax.jpg)
A trial paddock of the latest genetically modified cotton in NSW's Macintyre Valley this past season showed great promise for managing summer weeds.
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The crop eventually yielded less than expected only due to the cold start and hot Christmas period. Where it performed well was in controlling the huge burden of weed dominating after a good run of wet summers.
The trial of the new Bayer Roundup Ready XtendFlex trait on country north of Delungra highlighted the usefulness of this herbicide tolerant variety when it comes to managing heavy summer weed pressure.
"My clients were really happy with its ability to manage weed control," said McGregor Gourlay agronomist Alice Jorgensen. "After a few wet years they had a massive fleabane seed bank and the ability to spray over the top of the crop did a fantastic job. The year before they couldn't get on top of the weeds and there was a yield loss."
![McGregor Gourlay agronomist Alice Jorgensen, Delungra, is happy with new genetically modified cotton varieties and their ability to manage summer weeds.
McGregor Gourlay agronomist Alice Jorgensen, Delungra, is happy with new genetically modified cotton varieties and their ability to manage summer weeds.](/images/transform/v1/crop/frm/AiCzB4VqmYJMUfirK8QQiz/01018205-e209-4356-b452-692aa762af21.jpg/r430_242_2464_2419_w1200_h678_fmax.jpg)
Ms Jorgensen said there were still lessons to learn about growing cotton in dryland areas, with the crop more of an opportunity.
Third generation gene technology in Roundup Ready XtendFlex delivers herbicide tolerance against glyphosate, dicamba and glufosinate ammonium.
"While the first release of Roundup Ready traits gave glyphosate tolerance to young plants in the early establishment window, this was followed by Roundup Ready Flex, which gave season-long tolerance," Bayer national sales manager Mark Dawson said.
"With Roundup Ready XtendFlex, Australian varieties infused with this technology provide season-long tolerance for all three chemistries.
"The idea is to lessen reliance on glyphosate and manage weed resistance to this chemistry, as well as controlling a broader spectrum of problem weeds."
In general, herbicides work by blocking plant production of enzymes while the Bayer technology works by creating diversions or detours around these "roadblocks".
"This is different than the way in which Bollgard 3 makes cotton resistant to insect attack," Mr Dawson said.
"In that case the plant produces proteins that are toxic to the grub. In the case of Roundup Ready XtendFlex, genes allow the cotton plant to produce enzymes in another way."
With glyphosate suitable for grasses and Dicamba best for broadleaf weeds, including vines and milk thistle, the ability for a grower to combine the chemistry as a "double knock" is now available for the first time.
"The technology plugs the holes in glyphosate's armour," Mr Dawson said.
"The program works particularly well on feathertop Rhodes grass and fleabane."
In a win for growers, the cost is no higher using Roundup Ready XtendFlex.
"Some paddocks will need this sort of herbicide tolerant technology, others won't," said Mr Dawson.
"When a farmer needs to apply the chemistry, the technology is there. If they don't need it then we don't think they need to pay any extra for trait," he said.
Roundup Ready XtendFlex is commercially available for the first time this year.
The use of the chemistry containing dicamba, Xtendimax 2, will be limited to 50,000 under a permit to be issued by the Australian Pesticides and Veterinary Medicines Authority. Already that allocation is filled.
"We have had expressions of interest for much more area than that," Mr Dawson said. "While the gene trait is registered and has overseas approval and full registration with Australian trading partners, the APVMA want to make sure there is no impact from over the top spraying of dicamba, which could affect nearby summer crops such as soybeans, mung beans, grapes and citrus along with other cotton crops that don't carry the new gene technology. Currently it is ok to spray fallow country with dicamba but not over the top of crops."
Along with providing traits, Bayer is providing half-day training in correct spray management, including an emphasis on coarse droplets, correct rig set-up and awareness of spray drift conditions like the inversions last season that amounted to $300 million worth of damage to cotton from 2-4-D.
Compared to other seed varieties there is evidence that varieties containing Roundup Ready XtendFlex produces higher yielding crops.