Grains Research and Development

Date: 01.06.2004

New tools give advance warning on blackspot

By Emma Leonard

Field pea growers will soon have new decision support tools - for the western and southern zones - to help them minimise crop damage from blackspot. Blackspot is estimated to reduce field pea yields by 15 percent.

The "Blackspot Manager" developed by the Department of Agriculture, Western Australia, forecasts onset and progression of spore dispersal from infected field pea stubble, and the incidence and frequency of ascospores during the growing season. To do this, the model assesses proximity to the previous seasons pea stubble along with rainfall and wind direction to estimate the probability of a blackspot infection occurring.

The WA researchers have found that the windblown spores are the key source of blackspot infection in field pea crops grown in the state. For this reason their model looks at the regional spread of blackspot.

"We looked at spore movement over 35 square kilometres, a huge test area," explains the departments Moin Salam. "The spore maturity section of the model was validated in the Geraldton, Northam, Pingrup and Scaddan districts, whereas the spread module was validated with growers at Scaddan.

"Using this extensive evaluation enables the Blackspot Manager to predict disease on a farm or a catchment basis."

In southern Australia, field peas are a major pulse crop and tend to be grown more frequently than in WA. In this region, the researchers have found that both wind and soilborne spores play a role in blackspot infection.

To account for this, the South Australian Disease Risk model (DIRI) brings together management factors such as the number of years since a pea crop was grown in a specific paddock, variety, the use of seed dressings and rainfall data.

DIRI has been developed by the SA Research and Development Institute (SARDI) in collaboration with INRA in France, and with support from United Grower Holdings.

"Sowing later reduces the incidence of blackspot, however yield is reduced with shorter growing seasons, therefore, sowing date is a compromise between these two," says SARDIs Jenny Davidson. "Our model not only allows growers to see the impact of adjusting sowing date on the level of blackspot disease risk, but also of paddock choice and the use or omission of a seed dressing."

DIRI for blackspot has been validated in the Lower North region of SA, and on Yorke Peninsula. Further validation is required for dry regions such as the upper Eyre Peninsula. Both models can help growers identify paddocks with a low disease risk and provide information linking the impact of sowing time to disease risk.

However, if there is no choice but to grow field peas in a particular paddock, the DIRI model can show growers how the disease risk is changed by different management options.

For more information on obtaining copies of the blackspot decision support tools contact:
WA - Moin Salam, 08 9690 2252, msalam@agric.wa.gov.au
SA - Jenny Davidson,08 8303 9389, davidson.jenny@saugov.sa.gov.au

GRDC Research Code: DAW 00018 & DAW 00023, program 3