RUSSIAN wheat aphid (RWA) feeding damage in a wheat crop at Grass Patch was last week discovered by Clarke and Stokes agronomist Lucy Burrows.
The wheat plants were at first node (GS31) and the crop was sown with an insecticidal seed dressing, with no RWA colonies found on the symptomatic plants.
As a result, growers have been urged to monitor wheat and barley crops for this pest.
RWA adults are only about two millimetres long, pale yellowish green with a fine waxy coating.
Their antennae are short, as are the cone shaped siphunculi (sometimes called cornicles).
A hand lens or smartphone macro lens may be useful to see them.
Department of Primary Industries and Regional Development entomologist Svetlana Micic said growers should start monitoring wheat and barley crops for RWA from GS30.
"Inspect the edges of crops, as this is where aphids often colonise first, or where plants are under stress, and look for streaking damage near the base of newly emerged leaves," Ms Micic said.
READ MORE:
"Unlike other aphids, RWA inject a toxin into the plant which causes a noticeable loss of green colouration across the crop and, on closer inspection, white, yellow, purple or red streaking, leaf curling, stunted plant growth and loss of vigour in the affected plant."
A few RWA can cause symptoms to appear on plants as early as seven days after infestation and plant damage symptoms will persist on plants, even if RWA colonies have not survived.
"RWA colonies are frequently found on the newest emerged leaves at the base," Ms Micic said.
"Growers should be mindful that RWA damage can look similar to herbicide damage, mite feeding damage or resemble wheat streak mosaic virus symptoms."
Luckily, this aphid is readily managed and growers should consider applying sprays only when threshold levels are reached.
