CROP monitoring will be imperative for grain growers this spring, with heightened activity forecast for aphids throughout the agricultural region.
The Department of Agriculture and Food (DAFWA) has received reports of cereal and canola aphids from the northern, central and southern regions, with more expected as the weather warms up.
Development officer Dusty Severtson urged people surveying for cereal aphids to send regular reports to the department to aid the industry's Russian wheat aphid surveillance program.
While Russian wheat aphid has not been detected in WA, Mr Severtson said crop monitoring provided an ideal opportunity to make reports using DAFWA's PestFax or MyPestGuide apps.
Mr Severtson said while aphid feeding damage generally resulted in yield losses of up to 10 per cent, Russian wheat aphid was potentially a more severe pest, having caused yield losses overseas of more than 80pc.
"Unlike other aphids, Russian wheat aphids inject a toxin into susceptible crops, such as wheat and barley, which can severely retard growth or under heavy infestations, kill the plant," he said.
"But we do not know how it will affect cereal crops in Australian conditions.
"The department is working with industry to protect the State's cereal crops and surveillance is important, so we encourage people to report both the absence and presence of the pest."
Mr Severtson said aphid populations would start to build up as the weather warmed up in coming weeks.
"Aphids are most likely to colonise the edges of crops first, so growers should monitor the 20 metre edge of paddocks for signs of aphids or crop damage," he said.
"When inspecting cereal crops it is best to get a close look by getting on hands and knees and inspecting the leaves down to the crown of the plant, where aphids may be hiding."
Grain growers can use the free MyPestGuide Crops app, an identification tool based on crop type, pest size and damage symptoms.
Mr Severtson urged growers to spray crops according to aphid thresholds to avoid unnecessary or prophylactic sprays.
"For barley crops the threshold for treatment is 50pc of tillers infested with more than 15 aphids with an expected crop yield of more than three tonnes a hectare," he said.
"This high threshold demonstrates that high populations of corn or oat aphids are required to actually reduce cereal grain yield and quality.
"Advanced canola crops are most sensitive to cabbage and turnip aphids, for which the threshold for feeding damage is when 20pc of plants are infested with aphids on the flowering spike."
Growers who have already applied a protective spray to prevent aphid virus transmission early in the season may need to do so again.
Growers should also consider the merit of beneficial predators when selecting a spray treatment and consider using a spray option that is soft on predators, such as pirimicarb.