Australian researchers are growing in confidence that an understanding of managing Russian wheat aphid, RWA, will eliminate the pest’s threats to winter cereal crops.

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

Grains Research and Development Corporation research investments are building  a biological and ecological profile of the pest to provide Australian grain growers with scientifically robust management tactics.

RWA is now present in many grain cropping areas of Victoria, South Australia, Tasmania and New South Wales. Despite the ongoing dry conditions in northern NSW, surveys as recent as last month have detected RWA as far east as Tamworth.

The aphid has remained undetected in Western Australia, the Northern Territory and Queensland. 

GRDC investment, ‘Russian wheat aphid risk assessment and regional thresholds’, investigate regional risk and management options for RWA.

South Australian Research and Development Institute, SARDI, the research division of Primary Industries and Regions SA, is leading the project with research organisation cesar.

Regional thresholds of the research has involved capture of data from a series of trials across south-eastern Australia, operated by a number of farming systems groups.

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

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

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

In an untreated trial plot at Loxton in SA, almost 30 percent of tillers were infested with aphids, enabling recording of yield-loss data.

Dr van Helden said 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.  It seems the overseas thresholds are, at this stage, acceptable for affected Australian grain-growing regions.

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

“However, with the results we are getting from these trials, we can now be quite confident in saying that in many situations there is minimal risk of Russian wheat aphid building up to damaging populations under Australian climatic conditions.”

The GRDC investment is also investigating how RWA survives during summer. 

This research is considered pivotal in determining the risk of infestation for winter-sown cereals and potential damage ahead of each new cropping season, as well as aiding RWA management planning and development of cultural controls.

The entire December 18, 2019 edition of The Weekly Advertiser is available online. READ IT HERE!

The entire December 18,, 2019 edition of AgLife is available online. READ IT HERE!