Blackspot Manager is a forecasting model for ascochyta blight (synonym: blackspot) of field peas. It can be used by agronomists and growers to help identify the best balance between early sowing and potential yield loss from ascochyta blight. Windborne ascochyta spores are released from infected stubble early in autumn, with timing depending on summer and autumn rain. Disease can lead to significant crop losses when the emergence of sown field peas coincides with spore release. Blackspot Manager calculates when the majority of ascochyta spores (~60%) have been released from field pea stubble and risk of infection is reduced to a low level.
DAFWA Crop Disease Forecasts 2017 contains predictions of low, medium or high blackspot risk for sites in NSW, SA, VIC and WA over fortnightly periods. These forecasts are dependent on a rain event each week of at least 3.5 mm. If no rain occurs then the risk remains the same as in the first week of the forecast period. Growers can decide to delay sowing field peas until their region is designated as a low risk for blackspot, or if sowing at a high risk time, they can plan a foliar fungicide program to reduce the severity of blackspot in their crops.
The optimum agronomic sowing window for field peas in each of the districts is also shown alongside the forecasts.
Blackspot Manager is produced by the Department of Agriculture and Food Western Australia (DAFWA) and predictions are made for field pea crops in New South Wales, South Australia, Victoria and Western Australia. Forecasts are regularly updated from April through June, each year. You can also subscribe to the free SMS blackspot alert service. Text ‘Blackspot’ with you name and nearest weather station or location to 0475 959 932.
In 2017 the information from Blackspot Manager for South Australia shows that sowing field peas in early May is forecast as a high to medium risk for ascochyta blight in many districts. However a low risk is forecast for mid to late May, dependent on rainfall events.
If growers sow into a high risk window, there is an option for foliar fungicides where the potential yield of the crop is more than 1.5 t/ha. In this situation, crops can be sprayed between 4 to 8 nodes and again at early flowering with 2 kg/ha mancozeb.
Where crops have a yield potential less than 1.5 t/ha, then foliar fungicides are generally uneconomic and not recommended.
In short season districts, pea crops should be sown early, irrespective of ascochyta blight risk, as the yield loss from a short growing season is often greater than the yield loss from ascochyta blight.
View the latest Blackspot Manager forecast for South Australia here.
Predictions from Blackspot Manager for Victoria in 2017 indicate that sowing field peas in mid-late May onwards poses a low risk for ascochyta blight at all prediction locations except Horsham, Hopetoun and Swan Hill. Horsham and Hopetoun remain at medium risk until the end of May and for the Swan Hill region the blackspot risk may not reach a low level until mid-June.
As more rainfall events occur in Victoria the risk will reduce and it is important for growers to check the updated predictions each fortnight for the 8 areas of Victoria.
In some areas it may be unavoidable to sow field peas at a time still considered to be high risk for blackspot due to other agronomic pressures such as sowing windows. Growers may need to consider foliar fungicides for the management of blackspot and are encouraged to discuss their options with their local agronomist.
View the latest Blackspot Manager forecast for Victoria here.
The Field Pea Disease Management Strategy for the Southern and Western Regions (PDF 760kb) provides recommended management strategies to minimise disease in Field Pea.
The Pulse Australia field pea guide provides Variety Management Packages which should be consulted for up-to-date, specific variety information, and resistance ratings.