FOR the first time, Russian wheat aphid (RWA) activity has been reported in Geraldton.
The aphids were found in wheat at the Department of Primary Industry and Regional Development's (DPIRD) Geraldton research support unit.
Colonies of RWA and oat aphids were found on the same plants.
DPIRD research Scientist Saleh Adnan said RWA had become widespread across the grainbelt since being discovered in the Esperance region in August 2020, but this was the most northerly point for RWA occurrence reported so far.
"RWA has also been found at below threshold levels in wheat and barley crops in Cunderdin, Woodanilling and Grass Patch areas," Dr Adnan said.
"RWA can occur on a wide host range of more than 140 species of cultivated and wild grasses within the family Gramineae, with wheat and barley being the most susceptible.
"Oats are not considered to be susceptible to damage from Russian wheat aphids."
RWA are small, green and elongated, with very short antennae and an apparent lack of cornicles.
In addition to RWA, corn aphids and oat aphids are another two abundant species of cereal aphids in WA and they all have a slightly different appearance.
Corn aphids are light green to dark green in colour and are usually detected by the two darker patches at the base of each cornicle.
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Oat aphids are olive-green to greenish-black in colour and are mostly identified by a dark rust-red patch on the tip of the abdomen.
Dr Adnan said when monitoring for RWA, growers should look for streaking damage near the base of newly emerged leaves.
"Aphids prefer to feed on the base and sheath of younger leaves of plants and are often found on the last two leaves unfurled," he said.
"Damage symptoms include longitudinal rolling of leaves, forming a hollow tube inside which aphids conceal; whitish, yellowish to pink-purple chlorotic streaks along the length of leaves.
"Damage symptoms may appear a week after infestation."
While scouting for RWA, growers should keep an eye on the edges of wheat and barley crops, or on the stressed plants.
Symptoms of RWA damage can be confused with nutrient deficiency, herbicide damage, mite feeding damage or wheat streak mosaic virus damage symptoms.
RWA is manageable with the application of registered insecticides, however growers are always advised to apply sprays only if threshold levels are reached.
Researchers from Cesar Australia and the South Australian Research and Development Institute have developed a calculator to help consultants and growers decide if spraying for RWA is economically justified.
