Aschochyta Warning in Australian Chickpeas
SYDNEY - May 14/15 - SNS -- Chickpea growers in Australia have been warned to be extra vigilant about aschochyta blight in their crops after a significant increase in infected areas last year.
The Grains Research and Development Corporation (GRDC) said 19.7% of chickpea crops in New South Wales (NSW) and Southern Queensland were infected last year, compared to just 1.8% in 2013 and 5.2% in 2012.
NSW Department of Primary Industries (NSW DPI) senior plant pathologist Dr Kevin Moore said areas where ascochyta was found last year are considered high risk for 2015 crops and he urged growers to implement a fungicide management program.
"All varieties, including PBA HatTrick, should be sprayed with a registered ascochyta fungicide prior to the first rain event after crop emergence, three weeks after emergence, or at the three branch stage of crop development, whichever occurs first," Dr Moore said.
"In localities where ascochyta was found on any variety in 2014, inoculum will be present in paddocks intended for chickpeas in 2015; moreover volunteer chickpeas in 2014 chickpea paddocks are already infected with ascochyta and these provide additional inoculum for 2015 crops.
"Growers in these areas should apply a registered ascochyta fungicide prior to the first rain event after crop emergence, to all varieties with less resistance than PBA HatTrick as well as to PBA HatTrick. Monitor the crop two weeks after rain and if ascochyta is detected, consider a second fungicide spray."
Low Risk Areas May Not Need Preventive Spray
Dr Moore said localities where ascochyta was not found in 2014 were considered low risk and that PBA HatTrick, PBA Boundary and most GenesisTM varieties should not require their first ascochyta spray until the disease is detected. However, volunteer chickpea plants in these areas should be checked for ascochyta and if the disease is present, crops near those volunteers should also be sprayed.
He said low risk crops should be monitored two-three weeks after each rain event from emergence onwards and would require spraying if ascochyta was detected in the crop or found in the district on any variety.
"Ground application of fungicides is preferred. Select a nozzle such as a DG TwinJet® or Turbo TwinJet® that will produce no smaller than medium droplets (ASAE) and deliver the equivalent of 80100 litres water/hectare at the desired speed," Dr Moore said.
Inoculum for the 2014 ascochyta infections is believed to have resulted from dry summer conditions in 2012/2013 and 2013/14 which contributed to slow stubble breakdown and infection of volunteers.
"The 2014 experience begs the question of whether the ascochyta pathogen has changed. The short answer is we dont yet know because we have limited data on pathogenic variability in the pathogen population," Dr Moore said. "However, as a population of living individuals, we should expect it to change."
Research to determine if the unexpected number of 2014 infections, particularly on PBA HatTrick, is related to the changes in the ascochyta fungus has commenced and initial results are showing that the population varies both in ability to cause disease (pathogenicity) and time to develop fruiting bodies (latent period). However, there is no evidence that that this variability is in response to the widespread cultivation of PBA HatTrick.
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