Predatory insects are shaping up as the best weapon against the invasive Russian wheat aphid, strengthening the case for using insecticides as a last resort.
The Russian aphid was first confirmed in Australia two months ago in South Australia and quickly spread to Victoria.
Loading...IPM Technologies scientist Paul Horne said in the short time the aphid had been present, it had become clear there was more benefit in protecting other beneficial insects, than in automatically spraying the aphid.
"We find there's a whole range of predatory insects that eat aphids and they are not too fussy whether they are exotic or not," he said.
"Things like brown lacewings, hoverflies and ladybirds, they all eat aphids.
"So, the naturally occurring biological control is actually very powerful and very effective in most cases."
Dr Horne said the selection of an insecticide was important if those beneficial insects were to keep doing their job.
"If you choose the wrong one and kill the predatory species, then unless the chemical works absolutely totally on its own, you can make the problem worse," Dr Horne said.
He said the only cases where spraying insecticides would be the better option would be where there was an imbalance, with vast numbers of aphids and not enough predators to control them.
Dr Horne will be speaking about controlling Russian wheat aphid at farmer forums in Horsham and Lake Bolac in Victoria on Tuesday.