Eutypa dieback research targeting fungicide registration

Scientists from SARDI and The University of Adelaide have nearly completed a three-year project: ‘Optimising management of eutypa dieback’. The research, led by Dr Mark Sosnowski and Matthew Ayres of SARDI, has included field investigations and glasshouse trials to collect data that we hope will lead to the registration of effective fungicide treatments for use in Australia.

Mark explains that the fungus Eutypa lata infects cool climate-grown grapevines through pruning wounds, colonising wood of cordons and trunks and causing eutypa dieback, which gradually decreases the productivity of infected vines until they eventually die.

‘Fungicides to treat eutypa dieback that can be applied with sprayers need to be registered for use in Australia. To provide data to assist the registration of fungicides in Australia, we selected five alternative fungicides, three natural products and two surfactants for field evaluation over two years, based on the results from previous research,’ he said.

Treatments were initially assessed following application by hand at different concentrations, and the pruning wounds were inoculated with a high concentration of E. lata spores. A year later, treated canes were removed and assessed by isolation on agar. Four of the fungicides showed significant reduction in E. lata infection and efficacy increased with dose rate: Folicur (59–88% control), Cabrio (10–75%), Shirlan (8–58%) and Scala (31–53%).

The addition of surfactants provided no extra benefit in controlling the fungus, and natural products, such as garlic and lactoferrin, provided some reduction in E. lata infection.

Fungicide treatments were also evaluated in the greenhouse four weeks after application using a detached cane assay. The results of the greenhouse testing suggested it may offer a quick alternative method of evaluation.

Air-blast, air-shear, fan and recycle sprayers were trialled in three South Australian grapegrowing regions, with the aim of improving the efficacy of applying pruning wound treatments. Some sprayers were found to control eutypa dieback using a tebuconazole fungicide to a similar degree as hand-application, providing deposition was maximised by focussing the spray at the pruning wound area and using water volume of at least 600 litres per hectare.

Current information used in Australia about eutypa dieback and the similar disease botryosphaeria dieback is based on apricots (where eutypa dieback was first discovered) and overseas grape research, which has recently provided conflicting information.

‘Our industry needs local information applicable to grapevines. To further develop recommendations for maximising disease management for both eutypa and botryosphaeria dieback, we plan to investigate spore dispersal and the length of time that wounds are susceptible to trunk disease at different times of the pruning season, along with factors such as water stress, and we plan to seek potential new sources of resistance or tolerance to trunk disease,’ Mark said.

The researchers are in discussion with agrochemical companies. If the data provided is compelling, the companies will undertake the process of applying for fungicide registration with the Australian Pesticides and Veterinary Medicines Authority.

For more information contact Elise Heyes, GWRDC Program Manager, elise@gwrdc.com.au

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