Russian wheat aphids being found in cereal crops
- Grass Patch
- Condingup
Rachel Minett and Hayley Hill (South Coastal Agencies) have found high numbers of Russian wheat aphid (RWA) and associated feeding damage in early-mid tillering Scepter wheat and mid tillering Illabo wheat at Condingup. These crops did not have insecticide seed dressings applied. Rachel reported that one crop had RWA at threshold and was sprayed with a synthetic pyrethroid. After the spray, RWA numbers decreased to below threshold levels.
Henry Marsh (Nutrien) has also reported RWA causing feeding damage to tillering barley at Grass Patch. He noted that they were only noticeable in crops where the seed had not been treated with insecticide.
Growers are urged to monitor wheat and barley crops for RWA or signs of feeding damage, especially those that have not had an insecticide seed dressing and have been late sown. Oats are not considered to be susceptible.
If RWA are at threshold and warrant spraying then growers and consultants can refer to DPIRD’s 2024 winter spring insecticide guide.
In WA, RWA was first reported in the Esperance region in 2020 following Australia’s first ever detection north of Adelaide in 2016. Since 2020, they have been detected in all grain growing regions as far north as the Geraldton port zone.
How to diagnose Russian wheat aphid
RWA is a small pale green aphid, about 2 mm long, with short antennae and short cone shaped siphunculi (sometimes called cornicles). A hand lens or smartphone macro lens may be useful to see them. RWA are frequently found on the newest emerged leaves at the base of wheat or barley plants. For more information, refer to DPIRDs Diagnosing Russian wheat aphid page.
The other main cereal aphids in WA are corn aphids and oat aphids which have more visible protrusions at the base of their bodies. For more information on diagnosing these aphids, refer to DPIRDs Diagnosing cereal aphids page.
Unlike other aphids, RWA inject a toxin into the plant that causes:
- a noticeable loss of green colouration across the crop
- white, yellow, purple or red streaking
- leaf curling
- stunted plant growth, and
- loss of vigour in the affected plant.
Monitoring and management
Start monitoring wheat and barley crops for RWA from GS30, by inspecting the edges where aphids often colonise first, or where plants are under stress. Look for streaking damage near the base of newly emerged leaves, while keeping in mind that RWA damage can look similar to herbicide damage, mite feeding damage or can resemble wheat streak mosaic virus symptoms.
Very low numbers of RWA can cause symptoms to appear on plants as early as seven days after infestation. Plant damage symptoms will persist on plants, even if RWA colonies have not survived. It is important to get an accurate assessment of percentage of tillers with RWA, and not use damage symptoms as a measure of RWA presence. RWA is more likely to be detected on tillers and threshold feeding damage met if seed treatments have not been applied.
A guide to RWA management including a threshold calculator is available on the Grain Research and Development Corporation (GRDC) Russian wheat aphid page.
Further information on Russian wheat aphid thresholds in WA is available on GRDC’s 2023 Grains Research Update page.
For a list of insecticides with their toxicity to beneficial insects, refer to Cesar Australia’s Beneficials Chemical Toxicity Table.
Growers should consider insecticide options that are soft on predator insects if spraying.
For more information on beneficials refer to DPIRD’s Know what beneficials look like in your crop page.
Further information
For more RWA information refer to:
- DPIRD's Russian wheat aphid: production pest page
- Cesar Australia's Russian wheat aphid identification PestBites video
- GRDC's Russian wheat aphid page
- GRDC's Just how many Russian wheat aphids is too many podcast.
For more information on RWA, or other aphids, contact DPIRD Research Scientist Svetlana Micic in Albany on +61 (0)8 9892 8591.
Article author: Bec Severtson (DPIRD Northam).