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Sunday 24 September 2023 Dublin: 19°C
# a bitter pill
The world's citrus is being destroyed - here's what scientists are doing about it
Citrus fruits in Florida are facing a bombardment from a pest called a “Asian citrus psyllid”.

Citrus Greening Emergency AP / Press Association Images Citrus greening is causing worry for Florida growers. The condition is causing bacteria to grow on the leaf and fruit, eventually killing the tree. AP / Press Association Images / Press Association Images

ANYONE WHO DELIGHTS in freshly squeezed orange juice or eats grapefruit for breakfast should take a moment to stop and savor the taste of those citrus fruits. Many of them are at risk of being destroyed by a disease spread by an invasive pest that’s been sweeping across the citrus-producing regions of the world.

“It’s horrible — it’s a disaster,” says Fred Gmitter, a professor of horticulture science at the University of Florida Citrus Research and Education Center.

It might be time to kiss your OJ goodbye, unless science steps in to save the day.

At least 70% of Florida’s citrus trees are already infected by the disease, known as citrus greening, huanglongbing, or occasionally just with an ominous “it,” as in “It’s here.”

Florida’s citrus crop this year is the lowest it’s been in 30 years, and agricultural authorities have continued to lower their production estimates. Orange-juice prices are up nearly 20% this year alone and will continue to rise. The disease was a major factor in the lime shortage that made the price of a box of Persian limes jump from $18 to $85 last December. Prices could jump higher for oranges. Researchers and growers say that if a cure isn’t found, the entire $9 billion Florida citrus industry could be destroyed.

A Big Hit To Breakfast

Citrus Disease Detected AP / Press Association Images A trap designed to catch the Asian citrus psyllids that carry the disease to citrus trees AP / Press Association Images / Press Association Images

The disease first appeared in Florida in 2005. It is caused by bacteria spread by a 4-millimeter-long bug called the Asian citrus psyllid, which looks a little like an aphid but is much more active. The bacteria turns fruit sour and changes its color. These unripe fruit fall from the trees and eventually die.

Researchers, citrus growers, and agriculture officials are doing everything they can to stop its spread. The desperate nature of the effort elucidates the severity of the problem.

The U.S. Department of Agriculture recently allocated $31.5 million to fight the disease in Florida, a number that seems like a lot until you consider that Florida’s citrus industry is worth $9 billion and employs 76,000 people. Initiatives have been launched to stop the spread of the disease in Texas, Georgia, and Louisiana.

Researchers and growers all over Florida are breeding trees and trying to find hardy ones that can survive long enough to get the pests under control. Part of the USDA’s money is going toward approving new varieties of citrus.

In California — which produces 80% of the whole-fruit citrus eaten in the U.S., an industry worth $2 billion — the USDA recently promised $1.5 million to help release a million parasitic Pakistani wasps each year. The wasps hunt the psyllid bugs, which have spread to the state, though no one is certain how far they’ve spread the greening bacteria yet.

Around the world, in Asia, Africa, and South America, similar efforts are underway. In Brazil, the only place that produces more orange juice than Florida, diseased orange groves are cut down entirely and healthy trees are planted in new groves, hopefully far enough away that the bugs won’t find and infect them.

But alone these measures haven’t been sufficient. The wasps can, at best, slash the psyllid population by a third. Eliminating diseased trees hasn’t stopped the disease from spreading from country to country and even continent to continent. Short-term strategies are like putting a Band-Aid on a gunshot wound, though they may help farmers who are “hanging on by a string” stay in business a little longer, Gmitter says.

Without being able to cure the disease, greening will continue to leave millions of acres of trees devastated and put global citrus production in peril.

Citrus Greening Emergency AP / Press Association Images A dead orange tree in a grove in Florida AP / Press Association Images / Press Association Images

Science To The Rescue

The psyllids are hard to kill because they spread so rapidly, though massive insecticide sprayings have occasionally helped large commercial growers stave off disaster for a year. But the next big issue is that the bugs are becoming resistant to pesticides; they survive these chemicals meant to kill them. The price of citrus is rising rapidly and will continue to do so as the fruit becomes scarcer.

Some researchers think this blight attacking our beloved oranges will be the thing that persuades Americans to accept genetically modified organisms. There’s hope that GMO citrus with a string of viral DNA would be resistant to the disease. In an article on citrus greening in The New York Times last summer, Ricke Kress, the president of a company in charge of 2.5 million trees and one that squeezes juice for Tropicana and Florida’s Natural, was quoted telling his boss “the consumer will support us if it’s the only way.”

Gmitter thinks that if GMO citrus tree used a gene from another citrus fruit, it might be easier to get people to accept it. But genetically modified citrus trees will still take time to create and can be expensive.

healthy orange tree rafael-castillo / flickr A blight-free orange tree rafael-castillo / flickr / flickr

Recently, another potential cure for the disease may have been uncovered. A study from the University of Florida showed that a chemical called benzbromarone that’s occasionally used to treat gout in humans (though not approved in the U.S. for concerns about effects on the liver) was able to stop the bacteria in about 80% of trees that were tested.

Still, approving a new treatment chemical would probably take five to seven years at least, according to the University of Florida Institute of Food and Agricultural Sciences researchers who discovered the chemical’s potential. Even then, there’s no guarantee that the treatment will work in the field or that the bacteria wouldn’t develop a resistance to it.

It’s time to think long and hard about what our orange juice, tangerines, and grapefruit are worth. They may not be around for much longer.

- Kevin Loria

READ: The ‘Fruit Whispering’ mystery has been solved… and here’s the campaign behind it

READ: Ireland has 68 types of apple – and now there’s a book about them

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