A species of aphid unseen in Australia until this earlier year is encroaching on crops in central Victoria.
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Australia was the only country in the world free from the Russian wheat aphid until May, when south Australian farmers first reported sightings of the bug.
But the aphids, which are carried from field to field by the wind, are on the move.
Landmark Bendigo agronomist Duncan Thomas said he had seen the insects in volunteer plants – crops that grow incidentally from stray seeds – in Dingee, 550 kilometres from the initial point of detection in Tarlee, South Australia. He had also spotted infestations in Mitiamo and Torumbarry.
The pale yellow critters, approximately two millimetres in length, inject toxins into the plant on which it is feeding, stunting the plant’s growth and leaving white, yellow and red markings on its leaves.
The RWA, which feeds on cereals like barley, wheat, oats and rye, is also asexual, meaning it can reproduce without a mate of the opposite sex.
While Mr Thomas said the the bug was currently in small numbers and should be considered “just another aphid” with which farmers must contend, he was uncertain what the pests would do in springtime.
Warmer temperatures from August could be cause for the insect’s gestation cycle to speed up, leading to a dramatic increase in their population. A serious infestation could result in 90 per cent of crops being lost, Mr Thomas said.
The Australian Pesticides and Veterinary Medicines Authority has since issued an emergency permit for growers to use pesticides in an effort to ward off the RWA.
Even though the aphid had natural predators, including the ladybug, it was unable to be eradicated, Mr Thomas said, describing chemical control efforts as a “juggling act”.
“We don't want to go out and spray a heavy amount of insecticides to knock out everything,” he said.
The Victorian agriculture department has warned against using chemicals on aphid-affected crops within two days of heavy rain forecasts.