The battle against rust – Research aims to protect organic blueberry growers

BLUEBERRY rust remains contained in Tasmania but growers and community members are urged to remain vigilant for signs of the disease throughout the berry season.

Over the past two years, researchers at the Tasmanian Institute of Agriculture (TIA) have been working to develop science-based solutions to help Tasmania’s organic berry producers protect their crops from blueberry rust by expanding the treatment options available.

A detection of the disease on an organic farm would pose a serious risk to crop productivity and limit market access.

This is a key concern for the Tasmanian blueberry industry which has an annual farm gate value of approximately $25 million (2019/20).

The project team, led by TIA Plant Pathologist Associate Professor Kara Barry, has conducted controlled glasshouse trials in Queensland and field trials in New South Wales to evaluate a range of organic crop protectants which are not yet approved for use in blueberry against rust.

The trials were conducted in those states by Staphyt, the New South Wales Department of Primary Industries and Southern Cross University as blueberry rust has been established there for many years, unlike Tasmania where it is still a regulated disease.

The best performing products for protecting crops against blueberry rust were found to be Eco-oil, Aminogro + Synertrol Horti Oil and Intervene with no significant differences found between these treatments.

Similar levels of control were obtained for Copper and Mancozeb, which are already in use for blueberry rust protection.

Anolyte (electrolysed water), Serenade Opti and EcoCarb Plus + Synetrol Horti Oil led to higher levels of rust.

High levels of blueberry rust occurred in the field during periods of high relative humidity, rainfall and mild-warm temperatures between 18 to 25°C.

The trial is currently being repeated to verify the results and then further trials will be conducted for selected products to obtain residue data that is crucial to support minor use permit application.

Nick Cruikshank, from Mountainvale Berries in the Tamar Valley, is pleased to see investment into research to support the productivity of the berry industry more broadly.

“While our business doesn’t cater for the organic market, we are very interested in the research that is happening as some of the products used by the organic sector have broad use across the industry with a lot of synergies,” he said.
“It would be great to see permits obtained and widely available for the use of new products to protect against blueberry rust if research shows they are beneficial.”

During 2021, Fruit Growers Tasmania hosted a workshop for growers which included an interactive session run by TIA Extension Officer Michele Buntain.

The workshop allowed growers to practise monitoring for disease and tackle a hypothetical but realistic scenario of finding blueberry rust symptoms in their orchard.

“The scenario planning workshop provided growers an opportunity to go through the process of managing a detection of blueberry rust in a safe and supportive environment with lots of shared knowledge and experience on hand,” Ms Buntain said.
“As part of their overall business plan, growers already take a proactive approach to reduce the risk of disease incursion through on-farm biosecurity and farm hygiene.”
“We wanted to help growers put a plan in place so they can avoid panic and have a process to follow if blueberry rust symptoms are detected in their crop.”

Ms Buntain said early detection was key as blueberry rust becomes more difficult to resolve the longer it is present in a crop.

She said monitoring was an essential activity and while the plan would be different for each grower and property, there were a few key things that should be considered:
• When to monitor?
• How often to monitor?
• Where in your crop to monitor?
• What are you going to look for?
• How many plants are you going to inspect?

“The first thing growers or home gardeners should do if they suspect blueberry rust is contact Biosecurity Tasmania,” Ms Buntain said.
“It may not be rust, so it is really important to get an accurate diagnosis. “Biosecurity Tasmania Officers, wearing protective gear, will visit the site to check plant symptoms through visual inspection with confirmation using laboratory microscopy and DNA testing.
“A site management plan will be developed to help growers manage the crop and prevent spread of the disease.”

The workshop was part of the project ‘Expanding crop protection options for control of blueberry rust’, which TIA leads in collaboration with Staphyt Pty Ltd and the New South Wales Department of Primary Industries.

It is funded by the Tasmanian Government through the Agricultural Innovation Fund.

TIA is a joint venture between the University of Tasmania and the Tasmanian Government