GM WATCH comment: Yet another example of farm management issues supposedly simplified by GM crops becoming ever more complex.
EXTRACTS: In central Queensland, it has been found that CBT [cotton bunchy top disease] is increasing and is most obvious in fields where Roundup Ready cotton had been planted...
The CRC reports that volunteer cotton can cause problems for resistance management of Bt cotton, reduce seed purity and act as early hosts for insect pest.
It also provides a conduit for carry over of harmful plant pathogens into the next season.
In the past, the broad spectrum herbicide glyphosate was commonly used to control volunteer cotton seedlings but this is not effective on Roundup Ready cotton.
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Control of volunteer cotton key to CBT disease fight back Australia
SOURCE: Cotton Catchment Communities CRC and Queensland Country Life weekly rural news service, updated daily by FarmOnline.
10 April 2007
The rising incidence of cotton bunchy top (CBT) disease is causing concern.
Control of volunteer cotton, by cultivation or herbicides, is central to the fight back, a R&D field has been told.
In central Queensland, it has been found that CBT is increasing and is most obvious in fields where Roundup Ready cotton had been planted, the field day was told.
The concerns over CBT were espressed at a Cotton Catchment Communities (CRC) research and development field day.
While we don't know yet whether CBT is increasing on the Darling Downs, we can take some preventative action control volunteer cotton, the field day was told.
The CRC reports that volunteer cotton can cause problems for resistance management of Bt cotton, reduce seed purity and act as early hosts for insect pest.
It also provides a conduit for carry over of harmful plant pathogens into the next season.
Volunteer cotton can be controlled by cultivation or herbicides.
In the past, the broad spectrum herbicide glyphosate was commonly used to control volunteer cotton seedlings but this is not effective on Roundup Ready cotton.
Herbicide options to control seedling cotton include Spray.Seed and Hammer.
These herbicides are also effective on Roundup ready seedlings.
The control of established cotton is far more difficult with herbicides but experimental data has shown good results after two applications of glyphosate + 2,4 D amine or Starane.
Note, however, that these options are not registered and involve two applications which can make it costly compared to the costs of mechanical control.
Ratoon cotton can only be controlled by mechanical means as no effective herbicides have been identified.