EFFECTIVE management of the “green bridge” over the coming months is said to place grain growers on the front foot in their efforts to control Russian wheat aphid (RWA) during the year.
Eliminating the green bridge – volunteer cereals and weeds – well ahead of sowing this year’s winter crops will reduce RWA host plants and thereby minimise the risk of crop infestation.
Crop pest experts, supported by the Grains Research and Development Corporation (GRDC), said RWA established most successfully where there is a continual green bridge of host plants over the summer/autumn period.
These host plants allow RWA populations to persist from one growing season to the next.
Green bridge control is therefore a key element of an overall RWA integrated management strategy that growers are encouraged to implement this year.
Entomologist Maarten van Helden, from the South Australian Research and Development Institute (SARDI), a division of Primary Industries and Regions SA (PIRSA), said it is important that growers remove all volunteer cereals and weeds at least four weeks before sowing this year’s winter crops.
Contributing to development of the GRDC’s new GrowNotes RWA Tips and Tactics publication, Dr Van Helden said green bridge control at least a month before sowing will drive down over-summering populations of RWA well in advance of crop emergence.
“Paddocks kept bare – either by spraying, cultivating or heavy grazing – for at least a month before sowing will protect crops from early infestation of RWA, enabling better establishment,” he said.
Now present in areas of South Australia, Tasmania and southern New South Wales, RWA has been the focus of several GRDC research investment undertakings which are providing the Australian grains industry with greater understanding of the pest and its potential impact, to inform management strategies, including the ‘FITE’ strategy which has been developed to provide growers and advisers with a simple guide to management.
Last year, Dr Van Helden and other scientists confirmed the RWA now established in parts of the nation’s south-eastern cropping regions is a single biotype.
This new knowledge, achieved through research investment by the GRDC, will underpin ongoing and future research efforts aimed at combating the cereal crop pest.
In addition to experiments to determine aphid biotype, the GRDC has invested in research to confirm susceptibility of commercial wheat and barley cultivars to RWA, assessing potential sources of plant resistance, RWA biology, ecology and economic thresholds under Australian conditions, an investigation into alternate hosts for RWA, trials looking at insecticide efficacy and development of practical resources for growers and advisers.
While plant resistance has been deployed as a management strategy in areas of the world where RWA is a serious risk, the aphid has responded through the evolution of new biotypes attacking these resistant plants.
The GRDC is therefore emphasising genetic plant resistance will not be “the solution” to RWA control, but will form part of an integrated pest management strategy that includes green bridge management, agronomic practices, strategic use of insecticides, and exploitation of natural enemies of the pest.
In addition to the new tips and tactics publication, RWA management options for growers are also outlined in the comprehensive Russian Wheat Aphid: Tactics for Future Control manual, which has been published by the GRDC and is available online.
Suspected new infestations of RWA should be reported to the Exotic Plant Pest Hotline on 1800 084 881.
