Stubble residue levels
Trials in SA, Victoria and NSW have shown the key factors in crown rot infection are the amount and distribution of cereal residue at planting and the inoculum level in the residue.
[Photo (left): Trials in NSW and SA have demonstrated significantly higher levels of crown rot inoculum underneath last year"s cereal stubble row than in the inter-row area.]
Professor Lester Burgess and his team demonstrated that two-year-old wheat stubble contained significant levels of crown rot, while Dr Grant Hollaway in Victoria found that if high levels of either Fp or Fc were present, more than a single year of break cropping is required.
The SA trials indicate that a two-year break from a crown rot host is required to reduce inoculum levels below the critical level for successfully growing bread and durum wheat.
But it is not simply a case of removing stubble to reduce inoculum level. Work by NSW DPI has shown that burning is not a quick fix for high levels of crown rot inoculum, as this does not influence the survival in crown tissue that is below ground. Trials in NSW and SA have both demonstrated significantly higher levels of crown rot inoculum underneath last year"s cereal stubble row than in the inter-row area.
By leaving stubble standing and sowing into the inter-row the severity of crown rot and common root rot has been limited in no-till systems. In preliminary trials conducted by NSW DPI in northern NSW in 2004, the number of plants infected by crown rot (Fp) fell by about 60 per cent when wheat was sown between last year"s cereal stubble row. Work on the impact of rotation and stubble management is continuing in commercial paddocks across all states.
Other trials are also looking at the impact of crop nutrition on crown rot as links between soil water, nitrogen status and disease severity are gradually being unravelled.
GRDC Research Codes DAV00062, DAS00032; additional projects DAN485, US316 and DAS00034
For more information: Dr Grant Hollaway, 03 5362 2111; Margaret Evans, 08 8303 9379
Region North, South, West