Big wet brings disease challenges for cotton industry

Recent cotton surveys carried out by NSW Department of Primary Industries (NSW DPI) has found that the cotton industry has been hit hard by a range of diseases following a cool and wet summer. 

NSW DPI plant pathologist cotton, Dr Kirkby said “The cool and wet season has certainly favoured various diseases that can threaten crop yield.” 

“The survey results across NSW reported increased incidents of cotton diseases including Sclerotinia, Black root rot, Verticillium wilt, Phytophthora and Fusarium wilt,” Dr Kirkby said.  

“The valuable information collected during the surveys helps cotton growers manage emerging diseases and improve yields. 

“The disease Sclerotinia, or ‘stem rot‘ was reported during February in rank cotton growing under centre pivot, lateral and irrigation systems in the Macintyre, Namoi, Lachlan, Macquarie and Murrumbidgee valleys.   

“Sclerotinia is responsible for causing dieback of branches and other crop losses. 

“The pathogen responsible for causing this disease has a large host range and is common on sunflowers, legumes and canola but rarely seen on cotton.   

“There is currently no chemical registered for use on cotton to control this disease. 

“Several fields suffering from severe Verticillium wilt were reported and was particularly evident in the Naomi valley with 88 per cent of the fields surveyed reporting an infection rate of 21 per cent. 

“Additional diagnosis was carried out by Queensland pathologist and Verticillium wilt expert, Dr Linda Smith, and the results confirmed that the strain was not linked to the exotic defoliating pathotype.  

“Further molecular studies are also being conducted to further clarify the pathotype present.” 

Dr Kirkby said that the wet conditions were also responsible for an outbreak of Phytophthora boll rot of cotton.  

“NSW results also reported boll rot at various levels in all fields surveyed with a mean incident rate of 4 per cent in the Murrumbidgee valley,” said Dr Kirkby.   

NSW DPI continues to work closely with other agencies and the cotton industry through the Australian Cotton Research Institute located at Narrabri.  

The Institute employs some 50 staff and leads the development of northern broadacre irrigated and dryland farming. 

The Annual Cotton Pest Management Guide and the Cotton Seed Distributors Trial Results book will publish the report and be available shortly. 

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