Russian wheat aphid has now been identified in NSW, as well as South Australia and Victoria.
PHOTO: Albert Gorman
The exotic cereal pest Russian wheat aphid (Diuraphis noxia) may be a new arrival in Australia, but wheat germplasm with some resistance to at least three of the eight known Russian wheat aphid (RWA) biotypes is also already here.
This germplasm is part of pre-emptive breeding research funded by the GRDC and conducted at Murdoch University in Western Australia.
However, it could still be several years before commercial varieties with resistance are available to growers. A key issue is identifying whether the breeding material in WA has resistance to the RWA biotype responsible for the incursion.
GRDC general manager crop protection Dr Ken Young says the GRDC is funding new research to identify which of the eight biotypes has arrived to help determine which germplasm to incorporate into wheat and barley breeding programs.
RWA injects salivary toxins into the leaf of the host plant during feeding, which causes wheat streaking and kills infested leaves. Breeding efforts seek to make the wheat plants more resistant to the aphid’s toxins, and different biotypes have different levels of toxicity to their hosts.
“We’ve already done the initial genetic work,” Dr Young says. “Now we can use differential lines of plant material sensitive to different RWA biotypes to help narrow down which biotype is involved.” He says this could also help trace the most likely source of the incursion.
Dr Young says the GRDC’s investment in previous research has put Australia about four years ahead of where it might otherwise be in efforts to develop RWA-resistant varieties.
Some major Australian wheat and barley varieties will be screened for resistance to RWA, although a previous screening in 2008 showed no resistance in any elite Australian material.
Wheat and barley material from international sources reputed to have resistance, as well as material from Murdoch University that has resistance to three aphid biotypes, will also be screened for resistance to the biotype now in Australia for potential inclusion in new varieties.
The GRDC is also investing in further trials of chemical control options.
Dr Young says efficacy trials conducted by the South Australian Research and Development Institute (SARDI) shortly after RWA was first identified supported the use of either chlorpyrifos or pirimicarb under Australian Pesticides Veterinary Medicines Authority Emergency Use Permit 82792 for emergency control.
The GRDC has now initiated a broader research program, with a wider range of commercially available foliar-application insecticides.
The agricultural research agency Peracto has been coordinating 19 trials in Victoria and SA to compare the relative effectiveness of commonly available insecticides including organophosphate, synthetic pyrethroid, carbamate and sulfoximine chemistries (Groups 1B, 3A, 1A and 4C modes of action).
The trials will also consider the effects of different doses, spray volumes and quality, and adjuvants, to help determine future economic thresholds for chemical control treatments.
Dr Young says while insecticides will be important for control in some instances, information from other countries indicates that natural enemies play a critical role in the long-term management of RWA through a more integrated approach to control.
A GRDC-funded project in partnership with SARDI and the Victorian Department of Economic Development, Jobs, Transport and Resources (DEDJTR) will closely monitor RWA populations at 16 locations across SA and Victoria.
This will help quantify the relationships between crop stage, crop symptoms, RWA numbers, parasitoids and other potential RWA predator populations, and yield impact under Australian conditions.
“The project will help to better understand RWA population development rates and develop flight-predictive capacity under southern Australian cereal crop conditions, including key factors influencing pest development,” Dr Young says.
The GRDC has also funded an extensive international review of information related to the biology and management of RWA, which will underpin the publication ‘Russian Wheat Aphid: Tactics for Future Control in Australian Cropping Systems’.
Dr Ken Young,
02 6166 4500
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