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.
DPIRD Crop Disease Forecasts 2018 are updated each week and contain predictions of blackspot risk (rated as low, medium or high). The forecast risk will decline if there is 3.5mm or more of rain each week. If no rain occurs then the risk for the forecast period will remain the same as in the first week. Growers can decide to delay sowing field peas until their region is designated as a low risk for blackspot, or if sowing when risk is high, 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 Primary Industries and Regional Development (DPIRD) as part of the GRDC National Pathology Decision Support project, 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 by texting ‘Blackspot’ with your name and nearest weather station or location to 0475 959 932.
South Australia and Victoria – Current situation
In 2018 early forecasts point to a high risk of blackspot in seedling field pea crops across most of South Australia and Victoria. The extremely dry summer and autumn has delayed the maturation of blackspot spores on field pea stubbles. This means the spores will be released with rainfall in late autumn and winter, when the new crops are emerging and establishing. Growers should prepare for a high risk of blackspot establishing in their crops. It is advisable to avoid early sowing.
Growers should aim to plant this year’s crop at least 500m from field pea stubble, and if downwind from the stubble, where possible, increase this distance up to 1km since the spores are wind-blown.
In medium to high rainfall districts, the sowing date can be delayed 2-3 weeks past opening rains without compromising yield. The spore numbers in the air will reduce over the 2-3 week window, so the blackspot risk will decrease. However, delayed sowing is not an option in low rainfall short season districts as associated yield losses will be greater than losses caused by blackspot disease. It is important to check the updated blackspot forecasts each fortnight.
Fungicide strategies are an option in crops that have a yield potential of at least 1.5t/ha. P Pickel-T seed dressing will reduce infection on seedling crops, and foliar sprays of chlorothalonil will reduce the spread of the disease. Sprays can be applied between 4-8 nodes; apply at 4-node if disease is present but delay towards 8-node if disease is not evident. A second spray at early flowering will reduce the spread of the disease in spring. For maximum effect, spray ahead of a rain event, since spores are spread during rainfall. Spraying after rain is generally ineffective. Please discuss your fungicide options with your local agronomist.
View the latest Blackspot Manager forecast for South Australia here.
View the latest Blackspot Manager forecast for Victoria here.
View the latest Blackspot Manager forecast for southern NSW here.
View the latest Blackspot Manager forecast for WA 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.