Pea model gives growers more choice

20 March 2008

SARDI plant pathologist Jenny Davidson 

South Australian pea growers have a new tool at their fingertips to decide the best possible sowing time to lessen the risk of a blackspot outbreak. 

The GRDC-supported Blackspot Manager is an on-line decision-making model in its final stages of refinement for SA growers. 

It identifies when early sowing is possible without leading to a high level of primary infection of the destructive fungus in pea crops. 

SARDI’s plant pathologist, Jenny Davidson says new research has found airborne blackspot spores are released into the atmosphere from pea stubble whenever it rains – even less than a millimetre or heavy dew can trigger releases. 

“This means summer or early autumn rains can lead to spores being dispersed earlier and exhausted by May – opening up the opportunity for farmers to get their seed into the ground before usual,” she said.  

“The upshot is, by using this model farmers will have more flexibility with their sowing times.” 

The model plots the activity of the spores from individual temperatures and rainfall figures for each pea growing regions across the state. It also factors in projected potential seasonal scenarios.  

“This then tells us whether it should be safe to go ahead and sow, or if planting should be delayed, in each separate region,” she said. 

“Up until recently, the information we’ve been giving farmers to reduce the risk of blackspot is to delay sowing two to three weeks past the opening rains. The problem here is that in low rainfall seasons or regions this can lead to a shortened growing season, which usually means reduced yields.  

“Some people using this model in 2007 found they were able to sow in May instead of June, and they were able to reap higher yields.”

The model was first developed in Western Australia by the Department of Agriculture and Food’s Dr Moin Salam, and has been used successfully in the west for several years. In contrast to Western Australia, South Australia has more pea growing regions, so the model is being validated in nine cropping areas across the state. 

“We’re still in the validation process, but we’ve had agronomists and consultants using it last year and more have shown interest this year. The trials will continue in 2009, but the indications are already showing that it’s proving to be successful - both with trials and farmers.” 

Ms Davidson says people can `road test’ the model online at www.agric.wa.gov.au/cropdiseases . This year’s information is expected to be available after Easter, with on-going weekly updates. Although the tool is easy to use, Ms Davidson strongly recommends farmers use it along with their agronomist or adviser to gain its full potential. 

“These recommendations are only focused on disease, and other elements needs to be factored into the planting process. The Blackspot Manager is a decision-making tool to help farmers get around just one of these important elements of growing peas. That’s why it’s important to bring in your agronomist to make sense of it all,” she said. 

Ms Davidson says other useful blackspot management methods include avoiding planting pea crops next to pea stubble, avoiding water logging, maintaining a five-year rotation between pea crops to reduce soil-borne inoculum and being aware that medic or clover pastures can increase the levels of the soil-borne disease inocululm. 

Further enquiries: Jenny Davidson – T: 8303 9389, E: Davidson.Jenny@saugov.sa.gov.au 
Blackspot Manager website: www.agric.wa.gov.au/cropdiseases