CANBERRA, Feb 5 (Reuters) - Torrential rain and flooding in northeast Australia may have destroyed as much as a million tons of sugarcane but has also swept away an infestation of rats, the chairman of a cane farm industry group said on Wednesday.

More than a metre of rain has fallen in some areas in recent days in a deluge that has killed two people and left swathes of land under water. Forecasters expect more downpours this week.

Flooding in Australia's largest cane growing regions around Burdekin and the Herbert River in hot and humid north Queensland is expected to decimate recently planted cane, the CANEGROWERS industry body said.

"It'll knock probably half a million tons to a million tons of cane off what would otherwise have been there," said CANEGROWERS chairman Owen Menkens.

That would cost growers around A$50 million ($31 million), he said.

A million tons less cane would reduce Australia's annual refined sugar output by about 130,000 tons, or 3%. Most Australian sugar is exported. Global production of refined sugar is about 200 million tons a year.

Floodwater has encroached on one sugar mill run by Australia's biggest sugar producer, Wilmar Sugar and Renewables, cut off another and damaged the rail tracks that take harvested cane to mills, said the company's operations manager Mike McLeod.

"It's too early to know the extent of damage to our cane rail network, but we have had reports of ballast washout and erosion," he said.

Australian sugar production is currently suspended for the wet season and will resume around May.

There is a silver lining to the deluge, however - rats that have infested cane fields will have been drowned and swept away, Menkens said.

"One thing's for sure, there's no rats left."

($1 = 1.5974 Australian dollars)

(Reporting by Peter Hobson; Editing by Kate Mayberry)

((peter.hobson@thomsonreuters.com;))