With conducive conditions currently prevailing, and disease carry over from 2016 means that growers are advised to monitor crops for Septoria Tritici Blotch in wheat.
Septoria, caused by the fungus Zymoseptoria tritici, has been detected in the Wimmera this season, with sightings also occurring in the southern Mallee.
At the recent Southern Mallee and Quambatook GAPP crops walks, organised by BCG, Septoria was found in a paddock in the Quambatook region.
While the disease is normally an issue in the higher rainfall districts, the stubble carry over from the large 2016 season and the recent rain events have seen the disease creep further north than in previous seasons.
The optimal conditions for Septoria are temperatures of 15 to 20 degrees Celsius, followed by the plant remaining wet for a prolonged period.
Surviving on stubble over the summer period, it is not until rain or heavy dew in autumn and early winter that cause wind borne spores to be released. These spores have the ability to travel vast distances.
The fungus can persist on stubble for more than one season and is dependent on the rate of stubble breakdown. Splash dispersal also occurs during the lifecycle, assisting the fungus to spread over a plant.
Due to the long latent period for Septoria, the 21 to 28 days between the crop becoming infected and visual signs appearing, identification of this disease can be difficult but being proactive is advised.
The reason for the call to get out to check and monitor crops is because research has shown that the disease can cause yield losses of greater than 50 per cent.
Symptoms of the disease are pale grey to dark brown blotches containing black fruiting bodies (called pycnidia) initially found on the lower leaves, and to a lesser extent on stems and heads. Entire leaves can be affected with lesions in severe cases.
These black fruiting bodies distinguish it from yellow leaf spot or nutritional issues, like aluminium toxicity and zinc deficiency. During wet springs infection can persist after flowering causing glumes to become diseased.
Early sowing, minimum tillage, stubble retention, wheat-after-wheat and growing susceptible varieties all increase the risk of Septoria.
A spray program similar to that used for other diseases (GS31 and GS39) is very effective however, know your varieties disease rating and utilise a good fungicide strategy to minimise the risk of developing resistance.
Agriculture Victoria plant pathologist Mark McLean and Canadian plant pathologist, Dr Kelly Turkington from Agriculture and Agri-food Canada, will be at the BCG Main Field day to discuss disease management, in particular yellow leaf spot and spot form of net blotch however, Septoria is likely to be discussed.
The BCG Main Field Day is on September 13 at the BCG main research site at Curyo, corner of Grogans road and Sunraysia highway, 25km North West of Birchip. For more information about the event visit www.bcg.org.au/events or phone 03 5492 2787.
This article was published in the Stock and Land, 7 September.
