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Russian wheat aphid in early tillering crops

What are the current recommendations for managing Russian wheat aphid in wheat and barley?

 

Russian wheat aphid (Diuraphis noxia, RWA) continues to be reported from wheat and barley crops in the Victorian Mallee and Northern Country, and the NSW Riverina. While early season reports revealed volunteer plants with RWA and associated damage symptoms, more recent surveillance indicates that RWA are active in some early tillering cereal crops, especially those grown from non-insecticide treated seed. A little surprisingly, there have been no confirmed reports of RWA detections in the northern part of NSW and relatively little range expansion in Victoria and southern NSW since late 2016. Experts expect RWA to spread further north with time.

Where RWA is found, it is not uncommon to find them co-habiting with oat aphid (Rhopalosiphum padi) and corn aphid (Rhopalosiphum maidis). These cereal aphids are much easier to spot than RWA, and are usually present in higher numbers. It is usually the symptomatic purple-white chlorotic streaking, stunting or rolled leaves that is noticed before the RWA itself. 

The Russian wheat aphid is elongated (left) compared to the globular body of the oat aphid (top right), and lacks the siphuncles or ‘exhaust pipe’ structure shown on the corn aphid (bottom right) (source: cesar)

 

RWA can cause damage (and impact crop yield) from the seedling to soft dough stage. Last year the climatic conditions, particularly in late winter-spring, worked in our favour and assisted with RWA control. While we can expect to see the growth of RWA slow with the onset of winter, some paddocks may require chemical control. If wheat and barley crops are currently harbouring RWA, adhere to the best available economic thresholds (ETs). ETs are yet to be established under Australian conditions but guidelines are available from overseas. Guidelines from the United States vary somewhat between regions, but for early season growth, an ET of 20% seedlings infested up to the start of tillering, and 10% plants infested thereafter, is recommended. If spraying is warranted, use softer chemistries (e.g. pirimicarb) to maintain beneficial populations.

 

Field reports

Bruce Adriaans – Landmark (Mallee, VIC)

Connor Byrne – Elders (Riverina, NSW)

Ellen Grinter –  Advanced Ag (Northern Country, VIC)

Craig Muir – AGRIvision (Mallee, VIC)

Angus Skinner – Landmark (Mallee, VIC)

Duncan Thomas – Landmark (Northern Country, VIC)

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