MELBOURNE, Australia – The worst locust plague in more than two decades is threatening to strike Australia, the world’s fourth-largest wheat exporter, after rainfall boosted egg-laying by the insects in major crop growing regions.

“There are hundreds of millions of dollars worth of crops and pastures that are potentially at risk,” Chris Adriaansen, director at the Canberra-based Australian Plague Locust Commission said in an interview by phone. “Tens of millions of dollars” will be spent during the southern hemisphere spring to reduce the effects of the infestation, he said.

The forecast plague could cost Victoria’s agriculture sector $1.7 billion if left untreated, the state government said Friday. Widespread egg-laying across south-eastern Australia has set the scene for the biggest hatching in at least 25 years, according to the commission, which describes locusts as the nation’s most serious pest species.

“The advice of leading scientists indicates the scale of the coming spring’s outbreak could be as bad as we experienced in 1973 and 1974 when locusts swarmed through much of Victoria,” state Premier John Brumby said Friday in a statement. “Prior to that, the last outbreak of this scale was in 1934, so we could be facing a once-in-a-lifetime locust plague with locusts swarming right across the state.”

Locusts are expected to hatch from August to October in Victoria, New South Wales and South Australia states, according to the commission. The first-generation spring hatching alone could occur over a total area of 4.4 million acres, the commission’s Adriaansen said.

“Egg-laying has happened, so it is a case of being prepared to try and knock down their numbers come September,” Victorian Farmers Federation President Andrew Broad said by phone from Bridgewater. The VFF, NSW Farmers Association and South Australian Farmers Federation have asked the federal government for additional funding to help farmers fight the insects.

The Victorian government said it will spend $36.6 million to fight the locusts, which belong to the same order of insects as grasshoppers. Rabobank Groep NV in April raised its wheat-output forecast for Australia to 21.8 million metric tons, little changed from last harvest, after the rains.

Australian farmers have mostly completed planting of winter crops including wheat and canola, with final output depending on favorable weather through the remainder of the year. Aerial pesticide spraying and ground-level controls by agencies and growers is planned to curb the spread of the locusts, according to the commission