What options do organic growers have during a biosecurity incursion? A case study with blueberry rust

A review of previous studies indicate that many organically approved fungicides have moderate field efficacy at best for the control of rust pathogens. This particularly poses a management challenge for organic growers when faced with a rust incursion. Blueberry rust is caused by Thekopsora minima, which was first detected in Australia in 2001 and has established widely in Queensland and New South Wales. It was first detected in Tasmania in 2014 and whilst the state was then declared rust free in mid-2016, several detections followed from late 2016 until the present. Infected premises are managed under strict site management plans, as part of the ongoing blueberry rust containment plan, which mandate hygiene protocols and include regular fungicide sprays and monitoring. Organically certified blueberry growers currently have access to only one registered fungicide, copper hydroxide. Trials are underway to compare efficacy of a range of suitable products to expand options for organic blueberry producers. Glasshouse trials using inoculated plants have demonstrated that a range of products (including biologicals and inorganic compounds) can significantly reduce rust severity with efficacy close to that of copper and mancozeb. Field trials in New South Wales using natural inoculation will be used to validate the field efficacy of these results.