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Published: 7 Sep 2020

Tae Ocean (Hillwood Berries)

Tasmanian blackberry growers are embracing research findings that offer a softer approach to managing the pest redberry mite.

Redberry mites feed on unripe blackberry fruit which causes uneven ripening where part of the fruit stays hard and red whilst the rest is black and ready to eat, making the fruit unmarketable. Redberry mites are so tiny they can easily escape detection until it really starts to cause problems.

Last season, Tasmanian blackberry grower Costa Berries worked with TIA to trial a softer pesticide program to give predators a head-start in managing redberry mite.

Alejandro Haro, Horticulture Manager for Costa Berries in Tasmania, explained their motivation for trialling the softer program.

“For us it is always important to investigate new control methods for our main pests and if they involve an alternative option to chemicals or the use of softer chemicals, we may find a greater benefit for our programs,” Mr Haro said.

TIA Entomologist and Project Lead, Dr Steve Quarrell, emphasised that managing a pest such as redberry mite required a whole of system approach.

“There’s quite a lot of detective work involved. It’s critical to understand not just the pest but also how other farm management practices could affect the mite’s predators, both the native species that are already there and the ones we deliberately introduce,” he said.

Research trials conducted in Tasmania and Victoria over the last two seasons involved the introduction of three different predator mites and implementation of a reduced pesticide program.  The most promising candidate from these trials is the mite Typhlodromus doreenae commonly known as Doreen.

Dr Quarrell said the results looked very encouraging for a combination of Doreen and a softer summer pesticide program.

“We were really stoked to see reduced redberry mite numbers in our Doreen test rows and even more so that this was matched with the reduced pesticide program,” he said.

Sally Kershaw, Driscoll’s Southern Field Representative, recommended a staged approach to introducing the new pest management program.

“We are really excited by the results so far but would encourage growers to trial the softer program with a few tunnels or a block before extending it to their entire farm. It’s about taking a level of risk that you are comfortable with so that you can hone your monitoring and management techniques on a smaller scale first,” she said.

Dr Quarrell said the next step would be to confirm that Doreen is happy to persist in the blackberry crop over winter or whether reintroduction is necessary each season. He said winter was also the best time to see what levels of redberry mite were lurking in dormant blackberry buds to help growers plan their management strategy for the next production season.

A recent workshop, hosted by major blackberry supplier Driscolls, brought growers together to learn some simple techniques for monitoring redberry mite in their dormant blackberry crops.

At this workshop, Dr Quarrell demonstrated a grower-friendly technique for extracting mites from buds developed by former University of Tasmania Agricultural Science student Hui Law.

“We see real benefits in monitoring as it gives growers a greater appreciation of both the pest levels in their crop and the beneficial insects and mites that need to be encouraged,” he said.

This project has been funded by Hort Innovation using the Raspberry and Blackberry Research and Development Levy and funds from the Australian Government. TIA is a joint venture of the University of Tasmania and the Tasmanian Government.

This article also appeared in Tasmanian Country on 4 September 2020.