The Russian wheat aphid.
Photo: courtesy of Michael Nash, South Australian Research and Development Institute (SARDI), a division of Primary Industries and Regions SA (PIRSA).
Growers urged to adopt a threshold-based management strategy in controlling Russian wheat aphid following the declaration that it is not technically feasible to eradicate RWA.
The National Management Group (NMG), comprising all Australian governments, Grain Producers Australia and Plant Health Australia, met on Wednesday (June 8, 2016) and reached a decision to move to a management approach. This decision now triggers 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 SA (PIRSA) and the GRDC are calling on growers to adopt a threshold-based management strategy that considers impacts on beneficial insects.
SA Research and Development Institute (SARDI*) science leader – entomology, Greg Baker, says growers should first consider the economic thresholds of when to spray for RWA. International advice supports an economic threshold of 20% of seedlings infested up to the start of tillering and 10% 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 a number of natural enemies which 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 600ml/ha or applying pirimicarb at 250ml/ha under an APVMA emergency use permit. Pirimicarb has less of an effect on beneficial insects and natural enemies of RWA compared to 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 (OPs). 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 South Australia’s Mid North on May 13, 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 percent mortality in the aphid.
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).
SARDI entomologists will be presenting on RWA and its management at GRDC-supported meetings next week at Karoonda (June 14) in the SA Mallee, Roseworthy (June 15) in the Lower North and Keith (June 16) in the South East. Consultants and growers are invited to attend.
PIRSA – Russian wheat aphid information (including fact sheets)
PestFacts newsletter – Russian wheat aphid in South Australia.
PestFacts newsletter – Russian wheat aphid in Victoria.
Plant Health Australia
GRDC ute guide – Russian wheat aphid
Biosecurity SA plant health enquiries
(08) 8207 7820
Exotic Plant Pest Hotline
(1800 084 881)
*SARDI is a division of Primary Industries and Regions SA (PIRSA).
Sharon Watt, Porter Novelli
Phone 0409 675100
National, North, Overseas, South, West