GROWERS and agronomists being able to identify Russian wheat aphid (RWA) will be critical for control of the pest, according to Department of Primary Industries and Regional Development (DPIRD) entomologist Svetlana Micic.
Speaking at the DPIRD Grains Industry Day, held at Optus Stadium last month, Ms Micic said within Western Australia to date, the aphid had only been found in Esperance.
"Our South Australian agronomy colleagues have noted this aphid has a preference for barley and it can cause up to 80 per cent yield loss," Ms Micic said.
"Unlike other aphids, RWA injects a toxin into the plant that causes streaking along the plant's veins that is white and purple in colour.
"Plant symptoms also include flag leaf curling, immaturity of grain head and a prostate appearance."
RWA appears quite different to other cereal aphids - it is generally light green in colour, has an elongated body shape, with distinctive black eyes which is very different to the rusty patches of the oat aphid.
It also doesn't have siphuncles, which both oat aphids and corn aphids have and it can be identified by its double tail (bifurcate cauda), however that can't be seen without a hand lens or a macro lens.
So far, Russian wheat aphid has only been found in the Esperance area, predominantly in cereal crops that did not have an insecticide seed dressing.
So far there has been no yield loss as numbers were well below the threshold.
While other parts of WA were monitored for the pest, no other sightings were made, but growers and agronomists need to be on the lookout.
"The easiest control measure of this aphid is the addition of an insecticide seed dressing," Ms Micic said.
"Registered foliar insecticides have efficacy on the Russian wheat aphid, but the issue is the aphids cause curling of leaves which can be difficult for the chemical to penetrate."
Ms Micic said that the GRDC website had an interactive threshold which depended on predicted crop yield and cost of sprays.
"The threshold can be as little as 5pc of the crop infected because for every tiller that is infested, that tiller has a yield loss of 0.28pc," she said.
"While this doesn't seem much, if you have Russian wheat aphid over quite a large paddock it can be a risk."
Research by the South Australian Research and Development Institute (SARDI) has shown barley is especially vulnerable to damage from RWA from early booting to the soft dough stage (growth stage 30 to 50).
As a rule of thumb, control is warranted if more than 10pc of tillers are infected.
Russian wheat aphid uses grasses, barley grass in particular, as its non-host plant and prefers temperature ranges of nine to 21 degrees Celsius.
While it won't reproduce below 4oC, it can double in number every 35 days.
"It has the potential to increase and while I anticipate it to mainly be a southern coast issue, we can expect that whenever there is barley grass, we may see this species," Ms Micic said.
