Huanglongbing, or greening disease, has cut Florida orchards, which supply 40 per cent of the world’s grapefruit, by 80,000 hectares or more than a quarter since 2006.

Industry development officer Nathan Hancock said once the disease and its vector, the Asian citrus psyllid, enter growing areas it appears impossible to halt.

“Once the psyllid is present, as it is in California and Florida, costs of controlling it are enormous,” he said.

“The disease starves the citrus tree of carbohydrates by cutting off sap flow to and from the roots and there is no known cure.”

Mr Hancock said it was vital to keep both the psyllid and the disease out of Australia.

“Huanglongbing has troubled Asian countries, Mexico, Brazil and other growing regions for some time. It can lie undetected in orchards for several years, transmitted steadily by the psyllids and leading to death of the trees,” he said.

The US trip was organised by Citrus Australia, following a national risk assessment in 2009 and the recent creation of a national taskforce which is raising the awareness of Huanglongbing and its vector in the industry.

Huanglongbing and the Asian citrus psyllid are endemic to the Indonesian archipelago and East Timor and are also found in Papua New Guinea.

“Strict quarantine combined with constant vigilance to detect the Asian citrus psyllid is essential for Western Australia and Australia generally,” Mr Hancock said.

“Northern Australia is the front line for this pest and northern citrus producing areas including Kununurra could be vulnerable to entry through monsoonal winds.”

Travellers bringing infected citrus budwood, Indian curry leaf plant and ornamentals are another possible entry point.

The Australian Quarantine Inspection Service has listed citrus psyllid as a quarantine pest and intercepts and examines risk material.