A disease sweeping through South African beehives and infecting hundreds of thousands of bees, is posing a threat to fruit and vegetable farming in the country, warned an expert.

The only way to rid bee populations of American Foul Brood disease is by burning the infected hives.

South Africa has no quarantine regulations for insects, since it was the only country to avoid the disease for the past 150 years.

'It is extremely serious because it is a very contagious disease ... not only for honey but for agriculture. We need to use bees for pollinating fruit trees and vegetable crops,' said John Moodie, chairman of the Bee Industry Organisation.

The exceptionally contagious spore-forming bacterium, never before seen in sub-Saharan Africa, has broken out in the southern tip of the Western Cape province.

Some 200 hives are known to be infected already, with about 60,000 bees per hive, and the industry is awaiting assistance from the agricultural department to start burning hives.

The Western Cape's key fruit export industry relies on between 30,000 and 40,000 beehives to pollinate their fruit trees.

It is suspected the disease entered the country through infected honey, which by law has to be irradiated to destroy spores when it enters the country.

The disease poses no risks to humans.