Forecasts prompt new disease management advice
Author: Sarah Jeffrey | Date: 03 May 2016
Recent forecasts issued by the Bureau of Meteorology suggest an increased likelihood of above average winter rain and the onset of neutral to La Niña climate conditions by spring for northern Australia.
If the forecasts eventuate, NSW Department of Primary Industries (DPI) senior plant pathologist Dr Kevin Moore said it would have significant implications for ascochyta blight and botrytis grey mould (BGM) management.
At the Grains Research and Development Corporation (GRDC) Grains Research Updates in February/March, Dr Moore gave a series of management recommendations for ascochyta blight and BGM in 2016 crops but he said these recommendations had now changed.
“Current forecasts for above average winter rain and neutral to La Niña conditions in spring, plus evidence that the ascochyta blight fungus is changing and concerns about varietal purity, justify a conservative approach to ascochyta management this season,” he said.
“In addition, mild, wet conditions in winter will produce high biomass crops and this, coupled with a wet spring, will favour BGM.
“From an agronomic perspective, delaying planting will reduce the number of disease cycles to which the crop is exposed, however there’s always the danger that it may start raining and remain too wet to plant.
“Planting on wider rows (75cm or greater) provides better aeration, delays canopy closure and improves penetration and coverage by foliar fungicides.”
With a potential global shortage of chlorothalonil & mancozeb fungicides in 2016, Dr Moore is encouraging growers to secure on-farm stores of three to four ascochyta sprays in high ascochyta risk areas and two to three sprays in lower risk areas.
With respect to BGM fungicides, He said there would be strong demand from the lentil industry and advised growers to have one to two BGM sprays stored on-farm.
Additionally, Pulse Australia has obtained Minor Use Permits for alternative ascochyta fungicides and information is available on the Pulse Australia website.
Dr Moore recommends spraying all varieties rated Susceptible (eg Kyabra) or Moderately Susceptible (eg PBA Monarch), with a registered ascochyta fungicide before the first post emergent rain event, irrespective of whether ascochyta was detected in 2014 or 2015 in the surrounding district. However, he said Central Queensland growers should consult their agronomist prior to any spray applications.
“If ascochyta was found in your district in 2014 or 2015, or on volunteers over 2015/2016 summer, or if you are uncertain of purity of your variety, spray with a registered ascochyta fungicide before the first post emergent rain event. The purity of your variety is best determined by asking yourself `how confident am I that every plant in my crop of PBA HatTrick is a HatTrick plant’?” Dr Moore said.
“If ascochyta was not detected in your district in 2014 or 2015 and was not found on volunteers over 2015/2016 summer and you want to minimize your risk of ascochyta, spray with a registered ascochyta fungicide before the first post emergent rain event.
“If ascochyta was not detected in your district in 2014 or 2015 and was not found on volunteers over 2015/2016 summer and you are prepared to accept some risk of ascochyta, wait until ascochyta is detected before activating a fungicide program.
“Importantly, the fact that ascochyta was not detected in your crop or district does not mean it is not there. Indeed, we have had several cases where ascochyta was not detected in the previous two crops (eg 2014 and 2015) but became widespread on a subsequent crop or volunteers.”
If conditions favour BGM in 2016, Dr Moore said the disease would occur irrespective of what has happened earlier in the season, including the use of ascochyta fungicides.
If the canopy is likely to close by mid to late September, he advises applying a registered fungicide and consulting an agronomist regarding whether to apply a second BGM spray.
Bernadette York, NSW DPI media officer
0427 773 785
Sarah Jeffrey, Senior Consultant Cox Inall Communications
0418 152 859