The Grains Research and Development Corporation (GRDC) has advised Queensland growers and their advisors to ‘be alert, not alarmed’ by the pest, in a statement released late last month.

RWA is Australia’s latest broadacre crop pest, having first been detected in 2016.

It is now present in South Australia, Victoria, Tasmania and souther NSW cropping areas.

Research entomologist Maarten van Helden from the South Australian Research and Development Institute (SARDI) said it was inevitable the pest would soon be found in Queensland

“Last year, RWA was confirmed on the Liverpool Plains in northern NSW and we believe it will continue to spread into the cereal growing regions of Queensland,” he said.

“While RWA is a high priority pest, it is manageable and the best thing growers and advisers can do is regularly monitor crops for signs of the pest.

“There are very distinct plant symptoms associated with RWA and early detection will give growers time to make informed, timely, cost-effective decisions about the appropriate management strategy for their situation.”

Dr van Helden said it was critical suspected insect samples should be sent to the Queensland Department of Agriculture and Fisheries (DAF) in Toowoomba for formal identification. Confirmation of the presence of RWA would then enable state-based chemical permits to be enacted.

The southern-based researcher was in Toowoomba on a surveillance survey stretching through northern NSW and into southern Queensland. The survey is part of a broader project encompassing Tasmania, Victoria, SA and southern NSW.

The survey represents a major investment by the GRDC into understanding RWA. It is part of a collaborative investment, ‘Russian wheat aphid risk assessment and economic threshold’, led by SARDI in partnership with sustainable agriculture research organisation cesar.

This two-year-research project will investigate the role the green bridge plays in supporting RWA populations over the summer, and work to determine the regional production risks posed by RWA and the economic thresholds that will guide growers in effective management of RWA, taking into account growing regions, crop varieties and climatic conditions.

Despite collecting more than 120 samples from roadsides and farms in Queensland and northern NSW as part of the current survey, Dr van Helden said RWA had yet to be found.

“This survey included the key cereal growing regions in the northern region, so the Liverpool Plains, Tamworth, Narrabri, Moree, North Star, Garah, Boomi, Goondiwindi, Brookstead, Bongeen, Toowoomba and Dalby,” he said.

“We collected samples in Queensland from 10 sites and failed to detect any RWA.

“But growers and advisers need to remain vigilant and monitor paddocks regularly, because we are positive these pests will arrive in Queensland and early detection will give growers time to determine the appropriate action for specific crops.”

Dr van Helden recommends growers and advisers follow the FITE (find, identify, threshold approach and enact) strategy which has been developed as a simple guide to RWA management. It involves:

Weeds and volunteer cereals harbouring aphids may not necessarily show symptoms of infestation, so growers are advised to closely inspect grasses by unfurling leaves and checking inside partially emerged heads, paying particular attention to annual weedy barley grass.

Dr van Helden said neonicotinoid seed treatments may provide effective early season control of RWA. Preliminary evidence indicated the length of protection was expected to be equivalent to that observed for other cereal aphid species.

However, prophylactic use of neonicotinoid seed treatments is discouraged and should be targeted at those situations deemed to be of higher risk (early sowing, especially early sown barley crops; or areas where volunteer cereals and/or live aphids are identified prior to sowing).

Dr van Helden said crops should be monitored regularly throughout the season.

Crops can be infested under warmer conditions in autumn, during the early stages of establishment, from wingless aphids walking off nearby senescing hosts.

Intensive monitoring of early-sown crops, including cereals sown as pasture, should occur for the first four to eight weeks after sowing.

Populations frequently start to increase as temperatures warm in spring or typically from tillering onwards.

Stressed areas of the paddock are often the first to be infested and hence monitoring may specifically target these areas first.

“Growers are advised to adopt a threshold-based management strategy. Chemical control is warranted if infestations exceed thresholds of 20 per cent of seedlings infested up to the start of tillering and 10 per cent of tillers infested thereafter,” Dr van Helden said.

“Yield loss may be minimised through protection of the top three (major yield contributing) leaves. Current research investments by the GRDC will allow us to be develop more regionally specific thresholds as our understanding of potential RWA impact on regional production improves.”

He said growers should be reassured that the summer growing cereals were not under threat from the pest.

Growers and advisers should consider the following measures:

GRDC also has an online RWA resource with key information for growers and advisors.

Growers and advisers are encouraged to report occurrences of RWA to the Exotic Plant Pest Hotline on 1800 084 881. These reports will aid in improving understanding of RWA range and rate of spread.

For formal identification of RWA, Queensland growers and advisers can send samples to Melina Miles, DAF, PO Box 2282, Toowoomba, Queensland. For more details about sample collection contact Melina.Miles@daf.qld.gov.au.

In northern NSW samples can be sent to entomologist Zorica Duric, NSW DPI, Tamworth Agricultural Institute, 4 Marsden Park Road, Calala, New South Wales 2340.  For more details about sample collection contact Zorica.Duric@dpi.nsw.gov.au.