Chickpeas lose disease resistance

CONTROL: Dr Jenny Davidson says while AB infection is more severe in high-to-medium rainfall zones, disease control strategies are also needed in low-rainfall areas.

CONTROL: Dr Jenny Davidson says while AB infection is more severe in high-to-medium rainfall zones, disease control strategies are also needed in low-rainfall areas.

All chickpea crops in South Australia will need to be closely monitored this year for Ascochyta blight (AB) infection as all current varieties are now rated as either susceptible to moderately susceptible to infection. A virulence change in the AB pathogen of chickpeas has occurred, with severe AB infection detected in previously resistant chickpea varieties across both States in 2015 and 2016. SARDI pulse pathology principal research scientist, Dr Jenny Davidson, says while AB infection is more severe in high and medium rainfall zones, effective disease control strategies are also required in low rainfall regions as severe disease outbreaks can occur in these environments during wet seasons, as was the case in 2016.

“Moderately susceptible varieties will generally require three to four strategic fungicide sprays ahead of rain events, offering two to three weeks of protection, starting at six to eight weeks post-sowing,” advises Dr Davidson, whose research is supported by the GRDC.

“And susceptible varieties will require regular fungicide sprays every two to three weeks throughout the growing season in front of rainfall events.” 

As the pods of all commercial varieties are susceptible to AB, Dr Davidson says they will also require fungicide sprays during pod setting ahead of rain fronts to protect the pods from seed staining and seed abortion. 

Agriculture Victoria pulse agronomist Dr Jason Brand says growers also need to factor into their 2017 management strategies the impact of early sowing following recent rainfall throughout SA and Victoria, as rapid early growth can lead to a greater risk of AB infection. 

Dr Brand, leader of the GRDC Southern Pulse Agronomy program investment, reports that while outbreaks of AB were significant in Victorian chickpea trials last year, crops generally recovered well from the disease once conditions dried out.

He says the AB pathogen will survive on stubble and organic matter for a number of years, so growers must observe a minimum three-year rotation between chickpeas in the same paddock, and avoid planting adjacent to the previous year’s chickpea stubble.

It is imperative that all chickpea seed is treated with a thiram-based fungicide to prevent seed transmission of AB on to emerging seedlings.

Dr Brand says ongoing research into pulse diseases in the southern cropping region will also include further assessment of the impact of AB on seed quality.

Information on management of ascochyta blight in chickpeas can be found on the GRDC website at https://www.grdc.com.au.

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