Real estate is not the only industry in Florida to be suffering from an economic blight. While the Sunshine State ranks as one of the foreclosure capitals of America, its huge citrus fruit industry is fighting a disease that threatens to devastate the orange business within a decade.

The United States is the world's second-biggest orange producer, after Brazil, and Florida is the heart of the industry. Last year, according to the University of Florida, the state produced 15.3 million tonnes of oranges, grapefuits, tangerines and limes, grown on 530,000 acres of farmland, in a business worth $9 billion (£4.9 billion) a year.

Three years ago, the alarm bells began to ring when a farmer in Florida discovered that part of his orange grove had been infected by huanglongbing, a deadly citrus disease that originated in China. Huanglongbing (HLB) means “yellow shoot disease” and is called “greening” in the West.

According to Ron Bransky, a plant pathologist at the University of Florida's citrus research and education centre: “The disease is now widespread across the state. All counties in Florida with commercial citrus growers have got it. Once a tree is infected, it can take two or three years for it to show symptoms. At the moment we are trying to find out through surveys how much it has reduced production. We don't really know.

“Like any plant disease, you have to manage it, but at the moment there is no cure. Part of our strategy is that we recommend growers to dig up the infected trees and get rid of them.”

The pathogen affects productivity. It makes the oranges smaller, green, bitter and lop-sided. While an infected fruit is not harmful if consumed, few fruit companies are prepared to buy such oranges. The tree dies within a few years of being infected.

Dr Bransky said that the disease was damaging for farmers who had invested a lot of money in young orange trees and fertiliser, only to find themselves having to dig them up.

Citrus crops in Florida yield fruit once a year, with smaller fruits such as mandarins and tangerines picked from September and larger fruits harvested the following June. According to the University of Florida, most citrus growers are not diversified, so a reduced crop cannot be offset by other parts of their business. They face potential ruin if HLB spreads to their citrus groves.

The state's citrus farmers, who levy a tax on each other in addition to Florida state and federal taxes, have diverted $20 million of funds from advertising and marketing to launch new research programmes to find a cure for the pathogen.

The US Department of Agriculture regards greening as such a threat to America's farming industry that it defined HLB as among a group of potential bioterror weapons.

Citrus experts have been forced to apply for exemptions so that scientists and statisticians could access data and samples of the guilty bacterium Candidatus Liberibacter asiaticus, which is spread tree-to-tree by an insect, the Asian citrus psyllid. In the past, access had been restricted to FBI-vetted scientists, hindering efforts by the state to understand the infection and find a cure.

Scientists are hoping that gene therapy will hold the key to a cure. Researchers noticed that lemons and some limes in Florida appear to be resistant to greening.

Jude Grosser, also of the University of Florida, conceded that growing genetically modified citrus fruits could trigger a huge public debate, but added: “It will probably come down to the point where people have to decide whether they want orange juice or not.”

Not the only fruit

Biggest citrus producers (global share)

India (20 per cent)
Mediterranean Basin ( 15 per cent)
United States (14 per cent)

Biggest orange producers

Brazil
United States
Mexico
India

Biggest exporters of citrus fruits

Spain (25 per cent)
United States ( 14 per cent)
South Africa (11 per cent)

Sources: United Nations Conference on Trade and Development, UN agency. FAO 2004

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