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The highly damaging Russian wheat aphid, never before seen in Australia, was detected three weeks ago on a wheat farm near Tarlee, north of Adelaide, and then on other properties.

The pest can cause production losses of 75 per cent and yield damage in wheat, barley and oats crops, as well as make crops more vulnerable to other virus, bacterial and rust infections. With heavy Russian aphid infestations, crops are killed.

The insect has been found to have spread to farms more than 400km apart, from Clare in the northern wheat belt, Milang on the edge of the Fleurieu Peninsula, Naracoorte in the state’s southeast and Bordertown, close to the Victorian border, and the major wheat-growing areas of the Wimmera and Mallee.

South Australian Biosecurity chief Will Zacharin believes the 2mm-long, pale green aphid may have been blown on trade winds from infected South African wheat crops. “Given how widespread it is, we don’t believe it is possible now to contain or eradicate it; but that doesn’t mean we can’t manage it to minimise damage with the right insecticides,” he said.

The aphid, which is carried on the wind, clothes and farm ¬machinery, injects toxins into susceptible wheat, oat, barley and rice crops, curling and withering their leaves and weakening the plants. It also affects native grasses and irrigated pastures used by dairy and beef farmers.

Under threat is Australia’s $8 billion wheat industry and the fortunes of the nation’s grain-growers, who now will have to use additional, expensive insecticide sprays several times a -season to control the pest.

Grain growers in NSW and Victoria, where new barley and wheat crops are just emerging and the season was looking bright, are now on alert.

Grain Producers Australia chairman and Victorian wheat grower Andrew Weidemann fears the pest has spread so far so quickly that it is now endemic in the eastern grain states, even though it has yet to be detected in NSW or Victoria. He said a priority was to stop the pest spreading to Western Australia — so far apparently unaffected — where half of Australia’s 36 million tonne grain crop is grown in a good season.

Eventually it may be possible to breed resistance to the Russian aphid into new wheat and barley varieties but this probably would take four or five years.

South Australian Agriculture Minister Leon Bignell said it was a serious threat to the state’s $1.6bn grain industry, and the government was putting all possible resources into its detection.

Victoria’s plant health chief officer Gabrielle Vivian-Smith urged grain growers and agronomists to be watchful to ensure early detection and to avoid spreading the pest.