Researchers are battling to discover the cause of severe losses in lupin crops in north-eastern Victoria and southern NSW.
GRDC Southern Panel member and Kerang farmer Geoff Hunt said the disease or diseases are the focus of priority research supported by growers through the GRDC.
He said lupins are a very important pulse crop for the acid to neutral soils. "The roots of lupins become infected and this may occur from soon after emergence to crop maturity. The primary cause of these root rots is unknown but severe disease has been associated with both narrowleaf and broadleaf lupins, a range of management practices, waterlogged soils and severe soil-borne fungi," Dr Hunt said.
Sze Flett of the Institute for Irrigated Agriculture at Tatura said the incidence of root rots in lupins had escalated since 1992, particularly in the Dookie and Rutherglen districts where 5-10 per cent of growers had complete crop losses.
"As well, large costs have been incurred by growers who have had to replace failed lupin crops with an alternative crop such as Linola or canola," she said. "However, in acid soil areas lupins are the only viable grain legume option in rotations." Dr Flett said root rot symptoms included a blackened tap root with no lateral roots or nodules. Another root disease known as 'sudden death', which leads to the collapse of mature plants at pod filling, had also been seen in NSW.
She said a field trial has been established in a paddock badly infected by disease last season at Dookie. Samples of disease-infected plants will be used in the identification process. Researchers are also testing numerous fungicidal seed dressings and antibacterial agents.
Next year the research team plans other trials including time of sowing, cultivation, and sowing depth variations to see if these are associated with this major problem.