Plant pathologists have confirmed that poor growth in some southern NSW canola crops this season is, at least in some cases, the result of a virus previously unknown in NSW, beet western yellows virus.
While the majority of canola crops in southern NSW look exceptionally good, some paddocks are showing symptoms of severely stunted, brittle growth and cupped leaves with discolouring.
NSW Agriculture District Agronomist (Wagga Wagga) Greg Condon said reports, so far, have suggested that less than 10 per cent of canola crops in southern NSW are affected.
Mr Condon said unseasonably warm weather in autumn and early winter, combined with high autumn rainfall, resulted in extensive aphid activity.
"We believe the main carrier of the virus is the green peach aphid which has never been seen to be a major problem in canola crops before."
Mr Condon said: "Obviously, the full implications of the virus won't be realised until after harvest; however, information from Western Australia suggests that affected growers can expect yield losses of up to 15 per cent and grain with a lower oil content."
Boron deficiency too?
Mr Condon said beet western yellows virus may not be the only cause of poor canola growth in southern NSW.
"In some cases, the symptoms are also consistent with boron deficiency. Other aphid-transmitted diseases could also be affecting canola growth."
Researchers at the Wagga Wagga Agricultural Institute have sent some new crop samples away to be tested for stem nematode.
Growers should consult their district agronomist for further management advice.
Contact: Dr Gordon Murray 02 6938 1879