One of the world's most common banana varieties - Cavendish - is facing possible extinction, stoking concerns of a worldwide shortage.

A fungal disease called the Panama Disease TR4 is spreading to plantations across the world.

It is a big threat to the Cavendish banana, which about half of the world's population imports and eats.

Northland banana grower and Tropical Fruit Growers of New Zealand chair Hugh Rose told Morning Report anyone who was growing Cavendish bananas as a monopoly would be "doomed eventually, if they get that virus into their plantations".

"I don't think it's the last word for bananas."

He said banana varieties were spread across the world and they "mutate quite successfully in different soils and different conditions".

"Cavendish was developed - and I don't really know the history - in England as a banana. It's a laboratory-grown banana and each one is a clone and a direct replica of the other one.

"So when you plant out 100,000 trees, they're all identical and along comes the disease and wipes out the plantation. But no, never fear ... those experts in the science community will produce another variety."

Rose said "99.9 percent" of the banana produce in New Zealand was Cavendish.

He said he was a small collector. "I think about 40 odd different varieties. I'm always keen to get some more that's of edible bananas."

Cavendish varieties came from "various research stations and notably Israeli Cavendish, Honduran Cavendish, and of course the British".

However, the bananas grown in New Zealand were tastier, he said.

"Cavendish is grown mainly through a thick skin so it transports easily and [has] uniformity of appearance and size. Whereas the typical Auckland backyard banana is usually a variety known as Misi Luki ... and that has a much creamier texture to the flesh, much sweeter."

In Australia, the government has put out an alert on its website: "Panama TR4 is a serious banana disease that has been found on farms in Far North Queensland. It is caused by a fungus that lives in the soil. The fungus is not eradicable and can survive in the soil for decades without host plants.

"In some countries, it has had a devastating impact on industries and livelihoods. If not managed it has the potential to do the same in North Queensland."

This story was first published by RNZ