Russian wheat aphid building a profile across Australia

Russian wheat aphid building a profile across Australia

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Researchers have investigated the behaviour of Russian wheat aphids across the country since it was first detected in 2016 and have been able to understand how to help growers manage it effectively.

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Researchers have investigated the behaviour of Russian wheat aphids across the country since it was first detected in 2016 and have been able to understand how to help growers manage it effectively.

Researchers have gained greater confidence that the pest does not pose a major threat to winter cereal crops if growers and advisers take the necessary steps to limit its impact.

Scientists have been studying RWA under southern Australian conditions and within local farming systems since it was first detected in 2016.

Through research investments by the GRDC, a biological and ecological profile of the pest is being built to provide Australian grain growers with scientifically robust management tactics for the future.

RWA is now present in many grain cropping areas of SA, Victoria, Tasmania and NSW.

Despite the ongoing dry conditions in northern NSW, surveys as recent as November 2019 have detected RWA as far east as Tamworth.

The aphid has not been detected in Western Australia, the Northern Territory or Queensland.

A collaborative investment is being led by SARDI and PIRSA in partnership with sustainable agriculture research organisation Cesar.

The regional thresholds aspect of this research has involved capture of data from a series of trials across south eastern Australia, which are operated by a number of farming systems groups.

SARDI entomologist Maarten van Helden said the data on infestation levels, symptoms and associated yield would help to determine the regional production risk posed by RWA and the economic thresholds that will guide growers in effective management of RWA, taking into account infestation date, crop type and regional climatic conditions.

"Currently, Australian intervention threshold recommendations are based on overseas research which recommends a spray application when more than 20pc of all seedlings are infested up to growth stage 30 and more than 10pc of tillers are infested from growth stage 30," Dr van Helden said.

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The Australian trials so far have shown that a considerable amount of RWA population pressure is required before yield loss is incurred.

In one of the untreated trial plots at Loxton in SA, almost 30pc of tillers were infested with aphids, enabling yield loss data to be recorded.

According to Dr van Helden, the impact of that infestation was surprising.

"Despite this heavy aphid attack, the plants were still able to grow and produce normally," he said.

"Overall, yield loss in our trials has not been as high as expected when aphid numbers have largely been above the overseas threshold.

"Plants under drought stress are more vulnerable to aphid infestation and we have recorded yield loss in such situations."

Dr van Helden said he was confident that in many situations there was minimal risk of Russian wheat aphid building up to damaging populations under Australian climatic conditions.

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