Biosecurity officers and detector dogs stopped the two packages - one containing live, bacteria-contaminated asparagales shrub plants with heavy fungal growth and the other fig cuttings - at the Sydney Mail Centre.

Both species are known hosts of Xylella fastidiosa, which kills plants by damaging their water conducting system, which appears as leaf scorching.

It's one of the world's most devastating plant pests and has no cure.

An incursion could be ruinous for 10 Australian industries, including cherries, citrus, tree nuts, production nurseries, summerfruit and viticulture, Agriculture Minister David Littleproud says.

It can also impact significantly on a wide range of native plants.

"According to ABARES (Australian Bureau of Agricultural and Resource Economics), a Xylella fastidiosa incursion could cost our wine grape and wine-making industries up to $7.9 billion over 50 years," Mr Littleproud said in a statement.

"It has destroyed priceless olive tree groves in Italy that are centuries old and is known to infect more than 350 plant species in 89 plant families."

Australia is Xylella free, and keeping it that way is the country's top priority when it comes to plant pests.

Key to that is stopping the import of live plants to our shores, Mr Littleproud says.

"If you are considering purchasing live plant material from overseas, think again."

"Most live plants must not be imported to Australia unless the importer has a valid import permit."

Australian Associated Press