The triple threat of drought, bushfires and coronavirus has slashed international tourism, with bookings diving more than 30 per cent in the past 11 weeks.

The head of Tourism Australia has told a conference in Melbourne bookings have decreased 35 per cent since December.

Tourism Australia managing director Phillipa Harrison.

Bookings from China have dropped 11 per cent, with the federal government's coronavirus travel ban, which came into effect on February 27, a key contributing factor.

Phillipa Harrison, managing director of Tourism Australia, told the 2020 Visitor Economy Forum on Tuesday the Australian industry had been booming before 2020 and was on track to double visitor numbers in 10 years.