Mild, wet winter leads to emergence of leaf blight
Author: Sarah Jeffrey | Date: 18 Aug 2016
Faba bean growers in New South Wales are being urged to be vigilant about disease control after unusually high reports of Stemphylium blight this season.
NSW Department of Primary Industries senior plant pathologist Joop van Leur said Stemphylium blight is generally considered a minor disease in Australia, but reports suggest it is emerging as a “severe” issue this year.
“The 2016 growing season in the northern region has been relatively mild with a number of low-intensity, long-duration rainfall events that typically favour the development of leaf blights,” Mr van Leur said.
The Tamworth-based pathologist said little is known about the yield impact of Stemphylium blight, but growers are being advised to monitor crops closely and continue with normal fungicide programs.
Stemphylium blight is characterised by large grey-black necrotic lesions restricted to leaves only, often starting from the leaf edge. The appearance and distribution of lesions on leaves is quite different from that of chocolate spot, which is considered to be the major leaf blight in the northern region.
Mr van Leur said chocolate spot typically appears as small discrete reddish-brown lesions on leaves that after extended periods of leaf wetness increase rapidly causing severe leaf necrosis, as well as symptoms on stems, flowers and pods.
“Chocolate spot was found in a number of early sown crops, but the symptoms of Stemphylium blight are significantly different, so if growers have concerns about identifying leaf blight they should contact their agronomist,” he said.
Mr van Leur said susceptibility levels of varieties and breeding lines have been assessed and trials are planned to assess Stemphylium blight yield loss impact, as well as research to determine whether other factors such as herbicide injury or nutrient deficiencies increased the vulnerability of faba bean to this pathogen.
“Early reports also suggest that PBA Warda is more susceptible to Stemphylium blight than other varieties including the newest variety PBA Nasma.
“There is little information on the relative value of different fungicides on this pathogen, however growers are advised to continue with their normal fungicide programs and if they are concerned about levels of Stemphylium blight seek agronomic advice before making decisions about fungicide application.”
Joop van Leur
02 6763 1204
Sarah Jeffrey, Senior Consultant Cox Inall Communications
0418 152 859
GRDC Project Code UA00127, DAN00176