Management of blueberry rust HAL BB13002 Rosalie Daniel Elizabeth Macarthur Agricultural Institute, NSW DPI rosalie.daniel@dpi.nsw.gov.au

Blueberry rust (Thekopsora minima) Prefers warm (20oC), humid seasons, moist leaves Spread primarily by wind Damages leaves and fruit Where does it survive? Where do spores come from? When does it infect? Biosecurity Tasmania

Disease cycle Sexual cycle Asexual cycle NSW Sexual cycle Asexual cycle Hemlock From Eddie McGriff, University of Georgia Extension Agent, Coffee County, Georgia, on June 22nd, 2012 BLUEBERRY RUST - See more at: http://on-the-farm.com/category/blueberries/#sthash.l8IdnIyu.dpuf Uredinia form on the lower leaf Urediniospores reinfect blueberry in a repeating secondary cycle Secondary infection leads to rapid build up of pathogen and spread of disease In regions with mild winters where hemlock is absent, it is suspected that uredinia may overwinter on green leaves of blueberry and other Ericaceous hosts Where hemlock is present, telia form in leaves at the end of the season, leaves fall to the ground. Basidia arise from germinating teliospores and basidiosopres infect young hemlock needles in the spring. Aecia are formed, releasing aseciospores to infect blueberry leaves Many fungicides applied for other leaf spots will also have rust activity; this is particularly true of the strobilurin (Abound, Pristine, etc.) and DMI fungicides (Quash, Tilt, Orbit, Indar, Bumper, etc.). - See more at: http://on-the-farm.com/2012/06/22/blueberry-rust-2/#sthash.Y7JjkAGU.dpuf Caruso & Ramsdell 1995

Seasonal occurrence of rust

Chemical and biological fungicides and plant defence activators Field trial (cv. C99-42): Applied every 2 weeks from February – July 2014 Chemical/activator FRAC Mancozeb M3 P Pristine (boscalid & pyraclostrobin ) 7 & 11 P & S Dithianon M9 Metiram Tebuconazole 3 S Copper M1 Silica N/A NC

Development of rust symptoms * * Proportion of leaf area covered with rust pustules two months after last spray (September 2014).

Other chemical and biological treatments Lab and glasshouse trials: Chemical/biological/activator FRAC Cyprodinil (Chorus) 9 Cyprodinil & Fludioxinil (Switch) 9 & 12 Fenhexamid (Teldor) 17 Fludioxonil ( Scholar) 12 Pyraclostrobin & Boscalid (Pristine) 7 & 11 Azoxystrobin & Difenoconazole (Amistar) 11 & 3 Pyraclostrobin (Cabrio) 11 Procloraz (Octave) 3 Cyproconazole (Alto) Bacillus subtilis (Serenade) 44 Chitosan NC

What works? Spores are present all year, particularly when there is moisture No symptoms in trial until September (this year) Mancozeb, metiram, copper and pristine inhibited symptoms Dithianon and tebuconazole also inhibit symptoms, but residue problems Are the spores dormant over cooler months or do they infect and not develop? How does the fungus infect the fruit?

Options for management of rust Sanitation Source clean planting material Prune/remove infected and dead plant material Spray after pruning, at leaf flushes, particularly if conditions are warm and moist Identification and development of resistant varieties

Acknowledgements Maurizio Rocchetti, Costa Berry Exchange David Robertson, NSW DPI Damian Collins, NSW DPI Australian Blueberry Growers Association Horticulture Innovation Australia Limited Contact: rosalie.daniel@dpi.nsw.gov.au (02) 4640.6217