Russian wheat aphid discovered in WA
Russian Wheat Aphid (RWA) is a common pest with a growing presence across Australia’s key cropping regions.
After detection in South Australia’s mid-north in 2016, swiftly followed by emergence in Victoria and New South Wales, the pest has recently appeared in Western Australia. Without monitoring and proactive treatment, RWA can reproduce at a rapid pace and cause significant crop damage and yield loss.
Russian wheat aphid (Diuraphis noxia) is a high priority pest of cereal grains and can reproduce rapidly under the right conditions in wheat, barley triticale and oat crops. The primary mode of dispersal is through winged pests carried on prevailing winds or live plant material. RWA do not appear to be carriers of cereal viruses such as Barley yellow dwarf virus (BYDV).
RWA is relatively easy to identify by both its appearance and the damage it causes to crops.
Aphids present as:
- pale green colour
- approximately 2mm long
- short antennae
- elongated spindle like body
- two tiny tails at the rear end
- lack of excretion tubes/exhaust pipes.
The aphids secrete a toxin that causes leaf rolling and white (in warm weather) or purple to red (in cool weather) streaking on the leaves.
Damage appears first as patches of stunted or discoloured plants which resemble drought-stressed areas.
Heavily infested plants are often stunted and may appear flattened, with tillers lying almost parallel to the ground. From a distance the damage may appear as a general loss of colouration across the affected crop area. Later in the crop cycle, wheat awns can become trapped by rolled leaves, resulting in hook-shaped head growth, bleaching and reduced yield.
Life cycle/ seasonal patterns
Russian Wheat Aphid can reproduce across a large temperature range from 2°C to 25°C with the life cycle being sexual, asexual or a combination of both.
As with other aphid species RWA can increase their numbers greater than tenfold in less than ten days under idea (18°C to 21°C) conditions.
1. Green bridge – the host range for RWA includes 140 species of grasses, so removing volunteer cereals and grass weeds during summer as well as around production areas in crop can prevent infestation.
2. Plant timings and locations – early planting favours RWA infestation meaning that a good seed treatment is critical.
3. Predators – there are several species of beneficial insects such as wasps, ladybirds and lacewings etc that will be present in spring and contribute towards control of RWA. Spraying early when there is a low burden of RWA may only lead to easy colonisation by the pest later in the year with no natural predators.
4. On farm biosecurity – with Russian Wheat Aphid being also easily being spread through the movement of machinery and equipment limiting the movement near any crops suspected of infection may be beneficial.
Currently the established economic thresholds for spraying are if 20% of plants are infected up to tillering and 10% from tillering until head emergence. For a more customised approach use the GRDC/CESAR Action Threshold Calculator.
|Seed treatment options||Post emergent options|
|Gaucho (600g/L Imadicloprid) – 1.2 – 2.4L per ton||Lorsban (500g/L Chlorpyrifos) – 600ml per hectare|
|Cruiser 350FS (350g/L Thiamethoxam) – 1 – 2L per ton||Transform (240g/L Sulfoxaflor) – 50g or 100ml per hectare|
|Cruiser Opti 1.65 – 3.3L per ton||Aphidex (800g/kg) – 190g per hectare|
|Karate Zeon (250ml/L Lambda Cyhalothrin) – 40ml per hectare|
*High water rates of 100L+ are necessary to maximise coverage and penetrate the canopy down to the leaf curl where Russian Wheat Aphid prefer to position themselves.
**When using chemical options please be aware of the registered withholding periods on label as to grazing, cutting for hay and harvest as this could lead to maximum residue limits being exceeded.
If you detect Russian wheat aphid in your crop please report it via the MyPestGuide app.
Elders offers a range of crop protection products. View the range.
Article written by James Bidstrup, agronomist Elders Esperance.
For information and advice specific to your needs contact your local Elders agronomist.