GRAIN growers have been urged to monitor their crops for aphids as temperatures rise and the pests become more active.
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The Department of Primary Industries and Regional Development (DPIRD) received significant reports of canola aphids from throughout the grainbelt during winter, while reports of cereal aphids are increasing.
DPIRD officer Dustin Severtson has been recently surveying crops in the Great Southern and found varying densities of green peach and cabbage aphids in canola crops and isolated infestations of cereal aphids.
“Cabbage aphid seems to have been the most prolific aphid in Western Australia this year, especially in crops that have not already been sprayed,” Dr Severtson said.
“To date most cereal aphids reports have been oat aphids, especially in hot spots around the crop edges in the central agricultural region.
“However, our taxonomists recently identified a Sitobian aphid species infesting a wheat crop at Mt Barker.
“Whilst it is known to occur in WA and is less common, this reiterates the importance of proper identification of aphid species in the field in case it is exotic.”
Growers are advised to increase crop surveillance efforts and to report both the absence and presence of aphids to DPIRD via its free MyPestGuide Reporter app.
DPIRD grains biosecurity officer Jeff Russell said the reports would also help to identify any Russian wheat aphids (RWA), which have not been detected in WA.
Mr Russell said there had already been reports of RWA building up in Victoria and South Australia so it was important to remain vigilant and report both the absence and presence of the pest in WA.
“Russian wheat aphids are unlike other aphids, as they inject a toxin that can severely retard growth or, under heavy infestations, kill the plant in susceptible crops like wheat and barley, causing crop losses of up to 80 per cent,” Mr Russell said.
“It is difficult to identify Russian wheat aphids via sight, so it is important to capture any sightings with a photograph, which can be sent to the department via its MyPestGuide Reporter app for entomologists to identify.”
Plants affected by RWA may show whitish, yellow and red leaf markings and rolled or curled leaves.
“Plants with low aphid numbers may not show any symptoms and leaves so leaf sheathes should be directly inspected on tillers,” Mr Russell said.
“We encourage farmers and agronomists to look for discoloured cereal plants and examine them closely with a hand lens.
“Focus on surveying cereal crops and grass weeds for aphid pests, particularly near the base of newly emerged plants.”
Growers are reminded to strictly adhere to chemical registration thresholds and to avoid unnecessary or prophylactic sprays.
Dr Severtson said growers who had already applied a protective spray to prevent aphid virus transmission early in the season, may need to do so again.
“They 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,” Dr Severtson said.
Growers and agronomists can get up-to-date pest and disease information by subscribing to DPIRD’s weekly PestFax electronic newsletter by emailing pestfax@agric.wa.gov.au
