Russian wheat aphid
PHOTO: M.A. Nash
Grain growers across the GRDC’s southern region are being urged to make themselves aware of all their options in controlling Russian wheat aphid (RWA) following the declaration that it is not technically feasible to eradicate the pest.
The National Management Group (NMG), comprising all Australian governments, Grain Producers Australia and Plant Health Australia, met on 8 June and declared the pest endemic.
This decision now triggers the GRDC’s involvement in developing a plan around the research, development and extension activities required to inform the on-farm management of RWA.
As the industry moves from the eradication of RWA to a management approach, Primary Industries and Regions South Australia (PIRSA) and the GRDC are calling on growers to adopt a threshold-based management strategy that considers the impact on beneficial insects.
South Australian Research and Development Institute (SARDI) entomology science leader, Greg Baker, says growers should first consider the economic thresholds of when to spray for RWA. International advice supports an economic threshold of 20 per cent of seedlings infested up to the start of tillering and 10 per cent of seedlings infested thereafter.
In the majority of cases identified to date, population densities of the pest have been well below this threshold.
There are several natural enemies that attack RWA including parasitic wasps, ladybird beetles, lacewings, damsel bugs, hoverflies and entomopathogenic fungi.
Entomologists have already observed mummified and fungus-diseased RWA.
Mr Baker says growers should consider lowering the rate of chlorpyrifos to 600 millilitres per hectare or applying pirimicarb at 250ml/ha under an Australian Pesticides and Veterinary Medicines Authority emergency-use permit. Pirimicarb has less of an effect on beneficial insects and natural enemies of RWA compared with chlorpyrifos.
Victorian growers may also consider the application of omethoate or dimethoate at registered use rates in cereal crops.
Current information suggests that synthetic pyrethroids may not be as effective as organophosphates.
Growers are reminded to always refer to the product label and adhere to local and state legislation relating to pesticide use.
The first case of RWA was identified in a wheat crop at Tarlee in SA’s mid-north on 13 May, with infestations now stretching into Victoria. RWA populations are strongly regulated by weather conditions. Rainfall and drying winds can kill RWA outside the shelter of leaf rolls, with heavy rain events able to cause 50 per cent mortality.
Growers and advisers are advised to look in early-sown cereal crops and volunteer cereals on roadsides and in paddocks, and encouraged to report suspected sightings of RWA to the Exotic Plant Pest Hotline (1800 084 881).
Exotic Plant Pest Hotline
1800 084 881;
Biosecurity SA plant health enquiries
08 8207 7820;
Plant Health Australia;
Russian wheat aphid Ute Guide
Highlighting the true cost of in-crop weeds
The GRDC is every grower’s R&D department