Native buffer zones support predatory bugs

Native plant buffer zones support predatory bugs

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BENEFITS: The Melbourne University's Dr Linda Thomson was able to quantify the benefits of predator insects to orchardists and fruit and vegetable crop growers at a recent workshop.

BENEFITS: The Melbourne University's Dr Linda Thomson was able to quantify the benefits of predator insects to orchardists and fruit and vegetable crop growers at a recent workshop.

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Planting native trees near an orchard or paddock could help the "good guy" insects.

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ATTRACTING pollinating insects to orchards and berry and vegetable farms was the focus of a recent field day at Woori Yallock, in Victoria.

Planting a native plant insectary attracted a range of orchardists and crop growers to the demonstration sites – an orchard and a strawberry farm.

The field day was organised by the Port Philip and Westernport Catchment Management Authority (PPWCMA) and Agribusiness Yarra Valley.

One of the biggest outcomes of planting native buffer zones around crops to encourage insects, was the notable increase in predatory bugs that eat aphids, according to the presenters.

“Planting a native plant insectary enhances beneficial insect diversity, which can only benefit horticulture,” said presenter Dr Linda Thomson, of Melbourne University.

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Sticky traps and infield observations were used to identify and count insects.

Different species increased their population levels between four and eight-fold, and that increase was observed within only a few weeks, according to Karen Thomas, of the PPWCMA.

Among the predator insects, ladybirds, lacewings, spiders and parasitoid wasps,

Dr Thomson quantified the commercial value of the increased population of ladybird beetles at the trial sites.

“We valued the cryptoleamus at 64 cents each, spotted ladybird beetles at 66 cents each and chilocorus at 64 cents each. In season two, the 1400 ladybirds captured on site at Woori Yallock represented $900 value,” Dr Thomson said.

ON TASK: A bee pollinating blossom at Raynor's Orchard, benefiting from the native plant insectary surrounding the farm.

ON TASK: A bee pollinating blossom at Raynor's Orchard, benefiting from the native plant insectary surrounding the farm.

She also quantified the value of native vegetation, with a cost benefit analysis of $550/year increase in value after planting shelter belts around grapevines.

“We saw populations of hoverflies and other predatory flies increase seven-fold,” Dr Thomson said.

“Adult hoverflies feed on nectar and are pollinators. Their larvae are predatory. So attracting abundant numbers of hoverflies requires nectar-producing plants with flowers in Spring and Summer, ideally just before the warmer weather leads to aphid incursions.”

The presence of native flora also provided an increased population of pollinating insects and – at ground level – habitat for frogs, lizards, birds and small mammals.

Identifying and planting the appropriate native vegetation was important, according to Karen Thomas.

“It’s important to select the right plant species to ensure they are habitat for the beneficials you are trying to attract,” she said.

“Native plants have a long flowering season, which is beneficial for insects.

“Brown lacewings lay their eggs in native grasses, so it’s important to mow alternate mid-rows to protect insect habitat and control broadleaf weeds.

“The maggots of voriella flies are only about 1mm in size but they live on the outside of and kill LBAM caterpillars which like to hide among broadleaf weeds.”

VISIBLE: The Port Philip and Westernport Catchment Management Authority's Karen Thomas says it only takes a few weeks to see beneficial insects among flowering plants in a native vegetation insectary. This was a benefit in integrated pest management systems on farms.

VISIBLE: The Port Philip and Westernport Catchment Management Authority's Karen Thomas says it only takes a few weeks to see beneficial insects among flowering plants in a native vegetation insectary. This was a benefit in integrated pest management systems on farms.

Some predator insects were more likely to be found in the native shelterbelt than in-crop, according to Dr Thomson.

At Strawberry Springs, one of the trial sites, beneficial insects were found along the fenceline planted with native vegetation.

The results were measured in an established shelter belt and enabled owners Heather and Luciano Corallo to extend the native vegetation around their strawberry crops.

“The more research we do in integrated pest management, the more knowledge we have and can utilise on farm,” Mr Corallo said.

“Monitoring the insectary over time has increased our understanding of insect life cycles, predators and the use of IPM on our farm.

“It’s also about being aware of our product and what the customers want from us in growing our strawberries.”

ON SITE: Heather and Luciano Corallo saw at firsthand the benefits to their commercial strawberry crops of a native plant insectary.

ON SITE: Heather and Luciano Corallo saw at firsthand the benefits to their commercial strawberry crops of a native plant insectary.

However, an insectary was one of a range of management tools available to farmers, according to Karen Thomas.

“Farmers need to have the option to spray, because of the risk of new pest insects coming in. But if you have an insectary, you build resilience in your system,” she said.

“You also need to have a look at what effect that spray will have on your beneficial insects.”

She also recommended buying in some predatory insects to build up populations in the early stages of an insectary.

About 140 insect traps are being monitored by a grower group and Agribusiness Yarra Valley for the project.

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