Crown rot in winter cereals -Northern region

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*Information on crown rot symptoms and management is available in the article Crown rot in winter cereals

Dry seasonal conditions across much of NSW and Qld cropping areas favoured the expression of crown rot in wheat, barley and durum crops in 2017. Unfortunately, dry conditions during winter even resulted in crown rot significantly impacting on the growth of some barley crops during vegetative stages in central-west NSW (Figure 1). This is a reminder that barley is very susceptible to crown rot infection but tends to suffer less yield loss purely through its earlier maturity relative to wheat. This provides an escape mechanism which limits exposure to temperature and moisture stress during grain filling which exacerbates expression of crown rot.

Barley plant severely infected with crown rot during the vegetative growth stage in central-west NSW in 2017

Figure 1 Barley plant severely infected with crown rot during the vegetative growth stage in central-west NSW in 2017. Source: Campbell Muldoon, Warren NSW

However, if stress occurs during vegetative growth stages, such as in central-west NSW in 2017, the crown rot fungus is still triggered to proliferate in the base of plants which can even kill plants early in the season.  Crown rot was also evident primarily in durum crops, which are very susceptible to this disease, in south-west NSW. Interestingly, quite high crown rot levels were still evident in some wheat crops around Forbes in central NSW which were sown into paddocks that had a flooded canola crop in 2016. The crown rot fungus appears to have survived in the airspace between nodes in infected wheat stems from 2015 even when submerged in flood water for extended periods.

It should still be remembered that there were plenty of wheat, barley and durum paddocks with no evidence of crown rot or only low levels (5-10% whiteheads) in 2017, a season very conducive to disease expression. This is a result of growers implementing a range of management strategies to reduce inoculum levels such as rotation with non-host crops, inter-row sowing, grass weed control and growing more resistant wheat varieties. Growers are urged to not lose confidence in their crown rot management strategies. The 2017 season was an extreme test of where crown rot management strategies have progressed to in individual paddocks. Low infection levels in a very conducive season should be kept in perspective as crown rot is very difficult to eliminate from paddocks due to its wide host range and extended survival in cereal and grass weed residues. Most agronomists reported that the highest levels of crown rot in 2017 were in paddocks known to have poorer rotations so increased levels of whitehead expression under these situations was not unexpected. Whitehead expression was also noticeably worse in parts of paddocks which had an underlying subsoil constraint such as sodicity.

Testing

Growers or agronomists wishing to benchmark the relative success of their crown rot management strategies within paddocks are advised to submit cereal stubble sample post-harvest.

For determination of crown rot severity in infection levels which developed in 2017 wheat, barey and durum crops please collect 50 stubble butts (plants) in a random pattern across an individual paddock and place samples in a labelled paper bag (not plastic) and provide your name, paddock identifier (GPS location also if possible), variety grown, your address, mobile phone number and email address.

Growers or advisers can send samples to:

Steven Simpfendorfer, NSW DPI
4 Marsden Park Rd
Tamworth NSW 2340

To assess the level of risk for the coming season growers are encouraged to use a PREDICTA® B soil test

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