SA growers urged to keep paddocks ‘Free for February’ to control green bridge rust disease threat
SA growers are being urged to keep paddocks ‘Free for February’ to minimise the risk of rust and other diseases such as powdery mildew, and pests such as mites and aphids, surviving on a green bridge.
South Australian Research and Development Institute (SARDI) pathologist Dr Hugh Wallwork says that while a longer break without weeds would provide improved control and potential yield benefits, if all growers kept paddocks bare for February as a minimum, the risk of rusts and other disease and pest threats would be significantly reduced.
“It is critical that growers eradicate the green bridge as rust pathogens rely on green leaf material to survive and pass onto crops in the following season,” Dr Wallwork says.
“Growers must be vigilant and look for rust-susceptible weeds and crop volunteers not only in paddocks, but along fence lines, around sheds and silos. At least a month of no green growth is required to prevent disease survival.”
Dr Wallwork suggests growers adopt the target of Free for February and encourage other growers to do the same.
“The reason the month of February is key is that some regions are still harvesting in January, and some growers want early feed in March, so February is the bestchance for a full pest and disease break,” he says.
In South Australia in 2016, there was a higher than usual level of leafrust seen in wheat across the state.
“Leaf rust withstands summer temperatures better than stripe rust, so with a combination of high levels of the pathogen and most common wheat varieties having some degree of susceptibility, there is certainly a high likelihood of leaf rust carrying over to 2017,” Dr Wallwork says.
However, rusts are not the only disease concern from poor green bridge control. A summer green bridge also increases the risk of several other diseases such as powdery mildew and net blotches, which can survive in stubble but are made worse by volunteers, Dr Wallwork says.
“And of course aphids and mites that survive on a green bridge can act as vectors for important plant diseases,” Dr Wallwork says.
Field Crop Pathology, SARDI
GPO Box 397, Adelaide SA 5001