Act now to reduce Russian wheat aphid risk in 2018
Author: Sharon Watt | Date: 09 Jan 2018
Effective management of the “green bridge” over the coming months will place grain growers on the front foot in their efforts to control Russian wheat aphid (RWA) in 2018.
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), say RWA establishes 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), says it is important that growers remove all volunteer cereals and weeds at least four weeks before sowing this year’s winter crops.
Dr van Helden, who has contributed to development of the GRDC’s new GrowNotes™ RWA Tips and Tactics publication (now available at https://grdc.com.au/TT-RWA), says 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 prior to sowing will protect crops from early infestation of RWA, enabling better establishment,” Dr van Helden says.
Dr van Helden, who has been involved in GRDC research investments since RWA was first discovered in Australia in 2016, warns that RWA infestation is more likely in early-sown crops and that this should be factored into consideration by those growers who are increasingly electing to sow early for agronomic reasons.
He also recommends avoiding sowing crops into paddocks near areas where alternate RWA host plants are growing but cannot be eliminated.
The GrowNotes™ RWA Tips and Tactics publication states that use of neonicotinoid seed treatments for early-season control of RWA should be targeted only at those situations deemed to be of higher risk, such as early sowing (especially early-sown barley crops) or areas where volunteer cereals and/or live aphids are identified prior to sowing. Prophylactic use of neonicotinoid seed treatments is discouraged.
Now present in areas of SA, Victoria, 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.
Outlined in the new Tips and Tactics publication, the FITE (find, identify, threshold approach and enact) strategy involves:
- Find – Look for aphids and the characteristic plant symptoms of infection including leaf streaking or leaf rolling on cereal crops and grasses;
- Identify – Positively identify RWA by consulting with an industry specialist;
- Threshold approach – Before deciding on your plan of attack consider thresholds for control, the presence of natural aphid enemies in the crop, crop growth stage and potential yield losses;
- Enact – Take appropriate action: Manage your next steps including encouraging beneficial insects and protecting honeybees before implementing control options.
Last year, Dr van Helden and other scientists confirmed that the RWA now established throughout parts of the nation’s south-eastern cropping regions is a single biotype (having the same genetic make-up).
This new knowledge, achieved through research investments 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 been investing 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 that genetic plant resistance will not be “the solution” to RWA control, but it 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 via https://grdc.com.au/rwa-tacticsfuturecontrol.
Suspected new infestations of RWA should be reported to the Exotic Plant Pest Hotline on 1800 084 881.
Maarten van Helden
08 8303 9537