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Ongoing project

Integrated pest management of redberry mite, Acalitus essigi, on blackberries (RB17000)

Key research provider: University of Tasmania

What’s it all about?

Beginning in December 2017, this investment is tasked with developing integrated pest management tools and strategies for the rubus industry, with a focus on tackling redberry mite (Acalitus essigi) in blackberries. The mite’s feeding leads to damaged fruit with incomplete, delayed and/or uneven ripening, with affected drupelets being hard and coloured bright red or green.

Survey results

A fruit survey carried out across Australian growing regions (see previous project update) revealed the extent of the redberry mite (RBM) in Australian growing regions, with only two locations where the mite was not found: Corindi in NSW and Stanthorpe in Queensland.

The survey also showed that some cultivars are particularly susceptible to damage from RBM, and growers are managing the pest with chemical applications, which increase costs.  

Integrated pest management

To find out if integrated pest management (IPM) techniques can provide a viable alternative for managing RBM, the team reviewed IPM literature to look for promising techniques to help growers.

Trials have begun using some of these techniques, including removal of wild blackberries on-farm (since these may harbour the mites) and release of a predatory mite Typhlodromus occidentalis.

The mite has been released at four sites that include both Chester and BL454 varieties, some open field, some covered in polytunnels. Where possible, chemical management has been modified to allow predatory mites to flourish.  

Growth, yield and populations of pest and beneficial insect populations will be monitored with results reported as soon as available.

Grower updates

The team has kept growers up to date through the BerryLink e-news, an article in the Australian Berry Grower magazine, and via fact sheets (please see below) sent out to all industry members including those that indicated an interest in being updated throughout the life of the project during the initial industry survey.

Workshops have also been held in the Yarra Valley, Victoria and Launceston, Tasmania in November to provide an overview of the project, its findings so far and knowledge of RBM management techniques used overseas. Participants were given a demonstration of the mite sampling technique developed by the team (see previous project update), to find the mites, which are very small.

ACT NOW

The researchers reported findings from two surveys on redberry mite (RBM) as well as a new method of extracting the mite from fruit.

A survey of redberry mite incidence in blackberry fruit

Samples of blackberry fruit from 11 cultivars were collected from growers in Northern Tasmania and the Yarra Valley, Victoria (including Driscoll’s and open source varieties). Wild blackberries were also collected from both commercial blackberry production sites and roadsides.

The results varied to some extent by location, but the survey suggested that RBM, as well as other mites, prefer certain cultivars over others. This will be tested in future trials.

Another key finding was that wild blackberry bushes, both on and off-farm, harboured medium to high RBM populations, raising the possibility that these blackberries could be a source of the pest.

This will be investigated further in work to come.

A survey of growers

A second study surveyed growers to find out how widespread RBM is in commercial blackberry varieties, as well as how growers are currently managing the pest.

They found that the vast majority of growers correctly recognised the symptoms of RBM indicating good biosecurity awareness. Growers reported damage of up to 60 per cent, depending on the cultivar, management practices, crop age and season.  

A new method to extract mites from fruits

The team has also developed a better way of finding the tiny mites on blackberry fruit. The fruit is soaked in ethanol then the liquid is poured over black filter paper to easily see mites or other pests. This method is faster, and more effective than current practices and, importantly, accessible to growers and agronomists.

Field trial strategies for the 2018/19 production season will include changes to current chemical management practices, increased crop monitoring and predatory mite releases. Over-wintering RBM populations with blackberry buds have commenced in some Tasmanian locations. Ultimately, the team hopes to estimate RBM population sizes during the production season.

The project team are initially reviewing existing mite control measures, surveying growers to better understand the extent of the problem, and undertaking monitoring of mite and beneficial predator populations, looking at resultant damage across growing regions. These findings will then be used to develop a selection of potential integrated pest management (IPM) programs, which will be trialled and refined across growing seasons.

So far the researchers have been building contacts with growers, who have in turn been supplying fruit for the project’s first season of fruit surveillance, which is quantifying both redberry mite and beneficial mite populations in commercial crops across Australia. If you’re interested in taking part in this during the current or coming season, or in any other project activities, be sure to contact project leader Dr Stephen Quarrell at stephen.quarrell@utas.edu.au.

At the time of writing, a phone survey with growers was also being run to determine the current impact of redberry mite in commercial blackberry crops and the IPM strategies currently undertaken to control the pest, while a literature review on the mite and mite-related IPM in berry crops in Australia and overseas was also being completed.

Look for updates as this work progresses. Throughout the project, also look for workshops that will be used to share learnings with, and seek feedback from, growers, plus resources such as fact sheets and guides for implementing IPM approaches.

ACT NOW

Growers are encouraged to get involved in the project. If you’re interested in sharing your redberry mite experience with the researchers, and/or taking part in crop surveys and research trials, contact project leader Dr Stephen Quarrell at stephen.quarrell@utas.edu.au.

You can also read more about the project in this article, circulated in the media.

Related levy funds
Details

This project is a strategic levy investment in the Hort Innovation Raspberry and Blackberry Fund