Vigilance is essential if growers are to avoid costly yield losses from Russian Wheat Aphid (RWA) in winter cereal crops across southern and central New South Wales this season.
The Grains Research and Development Corporation (GRDC) is urging growers and advisors to undertake regular and thorough monitoring in wheat and barley crops following the detection of RWA in two crops in southern NSW.
A mixed population of corn aphid and RWA. Image courtesy of Melina Miles DAF.
This week’s identification of RWA at Erigolia, more than 300 kilometres north east of the initial infection at Barham, suggests the pest could be more widespread than expected in NSW.
RWA is considered a high priority pest by the grains industry due to its potential to cause significant yield losses in wheat and barley if not well managed.
Queensland Department of Agriculture and Fisheries (DAF) principal entomologist Dr Melina Miles recently visited South Australia and Victoria to inspect infected paddocks and discuss suitable management options for northern conditions.
She said conditions conducive to the usual cereal aphid species were also suitable to RWA and crops were particularly susceptible to yield loss if infestations occurred between stem elongation and flowering (Z30-59).
“There are a lot of aphids in crops this spring and growers shouldn’t assume aphids in cereals are just the usual oat and corn aphid. In the event of an RWA infestation, early detection in spring is critical to prevent yield loss,” Dr Miles said.
“It’s important to be familiar with the symptoms of RWA infection as they’re likely to be the first things you notice in a crop.”
RWA induce striking symptoms in wheat and barley including white streaking on the leaves (some varieties show reddening); rolled leaves with RWA colonies sheltering inside the leaves; and when infestations occur up to head emergence, a rolling of the flag leaf resulting in the head being trapped in the boot. In contrast, the oat, corn and rose-grain aphids produce no obvious symptoms.
“Plant damage is in response to direct aphid feeding so only the infested leaves and/or tillers show symptoms, which usually appear within a week of infestation,” Dr Miles said.
Characteristic streaking in wheat in response to RWA feeding. Image courtesy of Melina Miles DAF.
“Some of these symptoms are similar to those caused by wheat streak mosaic virus (WSMV) and phenoxy damage in cereals so we recommend closely examining symptomatic plants to determine the presence of RWA.”
Dr Miles said it was important that aphids were correctly identified to ensure an appropriate management strategy is implemented.
More information on identifying and sampling for RWA is available on DAF’s insect pest management blog 'The Beatsheet' and the recent GRDC Update paper for the northern region, available via this link.
The GRDC has also updated its popular Crop Aphids Back Pocket Guide to include information on RWA. The guide, which can be downloaded via this link, contains valuable information on aphid monitoring, aphid management (including measures to avoid the risk of insecticide resistance) and biological control.
Detailed information about RWA, including surveillance advice, identification and reporting, is also available on the NSW Department of Primary Industries website, which is accessible here, the Plant Health Australia website, which is accessible here, or the GRDC Paddock Practices article on RWA, available via this link.