More mites might be the key to help berries

Tasmanian Institute of Agriculture researchers think more mites could help growers get more blackberries to market


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Mites: TIA researchers think more mites could help growers get more blackberries to market. Picture: Supplied

Mites: TIA researchers think more mites could help growers get more blackberries to market. Picture: Supplied

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The mites are naturally found in the cooler southern half of Australia.

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REDBERRY mites cause blackberries to ripen unevenly, typically creating a berry that is half-black and half-red.

This damage can drastically reduce the number of first grade blackberries growers produce. 

So how do you stop these micro monsters in their tracks? 

Researchers think that increasing the number of predatory mites might be the answer. 

The Tasmanian Institute of Agriculture (TIA) is working with commercial blackberry growers across Victoria and Tasmania this season to measure the effectiveness of two different predatory mites, Typhlodromus occidentalis and Typhlodromalus lailae.

TIA researcher, Dr Stephen Quarrell, said T. occidentalis — affectionately called "Occi"—is a seasoned veteran when it comes to protecting crops.

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“Occi has been around for quite some time and is regarded as an efficient predator.  It’s more tolerant of a broader range of environments than some other predatory mites and fairly hardy when it comes to pesticide tolerance,” Dr Quarrell said.  

In contrast, T. laliae is the untested rookie with something to prove. Dr Paul Horne, a researcher from IPM Technologies, notes that T. laliae is a good bet for tackling redberry mite.

“This mite is naturally found in the cooler southern half of Australia, making it more likely to survive in these climates. It is known to feed on broad mite, which comes from the same family as redberry mite,” Dr Horne said.

Predatory mites were identified as a potential pest management solution after TIA surveyed crops last year in the early stages of the project.

Though some predatory mites were found, the populations were unbalanced.

“We found that predator numbers in commercial blackberry crops were extremely low relative to the number of redberry mites," Dr Quarrell said. 

Fungicides can often catch growers out as they don’t necessarily see these as being harmful to mites and predators. - Dr Stephen Quarrell

"This means we may need to tip the balance in favour of predators by supplementing the natural population with some commercially reared predators."

So how many mites is the magical number?

“For every 10 broad mites you need one predatory mite to effectively manage the pest. This is a good guide as to the ratio we are likely to need to manage redberry mite,” Dr Quarrell said.

Growers may be unknowingly giving redberry mites the edge over their hungry cousins, however.

While pesticides are often necessary in intensive berry production and can be a useful tool in pest management, it’s important to minimise unwanted impact on potentially helpful predators. 

“Fungicides can often catch growers out as they don’t necessarily see these as being harmful to mites and predators," Dr Quarrell said.

“Switching to registered fungicides that have low toxicity to predatory mites can help tip the balance in favour of predators.” 

TIA will closely monitor the fate of both the predatory and redberry mites in blackberry crops through both winter and the cropping season.

Rather than blanket treatment of harmful pests, it’s hoped that caring for predators may be a boon for the future sustainability of intensive blackberry production.

Additional information on TIA’s ongoing redberry mite project is available at http://bit.ly/redberrymite

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