It is a single celled bacterium, carried by a diminutive insect that lives on one family of plants.
This combination may eliminate a breakfast favorite. Orange juice. And more.
In China, it’s known as Huanglongbing (literally, Yellow Dragon Disease.) In the Philippines, leaf mottle yellows. In Taiwan, it’s libukin and in India it’s citrus dieback. But overall, it has the technical term of Citrus Vein Phloem Degeneration, or Citrus Greening disease. It is the worst disease of cultivated citrus known.
It is caused by the bacteria Candidatus Liberibacter. Insects called psyllids carry it. It can also be transmitted via grafting, which is ubiquitous in citrus cultivation. First described in 1929, it was first reported in China in 1943, then South Africa in 1947, then Taiwan in 1951. It is now endemic in every citrus growing region in Asia except Japan. And now, it’s leaped to Brazil, where growers are simply abandoning their citrus groves for other non-infected (for now) regions, Florida and California. It’s now in Texas. The bacteria is so damaging to citrus the United States has it classified as a bioterror tool.
The disease does what it says on the tin. It yellows the veins of the plant. It kills the leaves. Then the roots. Then eventually the entire plant. The fruit turns greenish and never ripens. It turns misshapen, lumpy and gross. It tastes bitter.
There is no cure. Absolutely none.
The NY Times and the New Yorker a few months prior both have written excellent pieces on the threat to the orange.
Citrus itself is pretty fascinating. The orange came to be when pomelos and mandarins were crossed thousands of years ago. The orange, like the vast majority of what we eat organic or not, has been modified. Most species are hybrids, even some found in the wild as citrus loves to hybridize. In Florida, only two varieties are blended to make the great Florida orange juice many of us love.
Now, growers are faced with some choices a good many of you are not going to like. They can wait for evolution to catch up with perhaps some handy human directed selection (and the orange could vanish from Florida before that even happens), or they can find a pest that preys on the psyllids (tough, because psyllids produce hundreds of offspring in their short lifespans and only one insect can infect a plant). They can douse the fruit with pesticides, something they already do. Some growers douse their trees in extra nutrients, hoping it gives the plants the strength to survive the infection. They can douse the fruit with antibiotics (which would be tough because the bacteria in question has never been cultured in the lab) or they can insert genes from other organisms into citrus so that it is resistant to the bacteria.
The National Academy of Sciences describes citrus greening as the greatest threat to the industry. I’ve seen estimates citrus could be gone from Florida within a decade or less.
But will people drink transgenic orange juice? The NY Times (and I highly recommend you read this article):
If various polls were to be believed, a third to half of Americans would refuse to eat any transgenic crop. One study’s respondents would accept only certain types: two-thirds said they would eat a fruit modified with another plant gene, but few would accept one with DNA from an animal. Fewer still would knowingly eat produce that contained a gene from a virus.
(the last sentence is interesting considering viruses insert their genes into us and our food all the time, all by themselves, completely naturally but I digress. There is a general lack of biological knowledge in the United States and that is a related issue but ultimately separate, for now.)
There is a great deal of fear about genetic engineering, and rightly so considering the business practices of Monsanto. Now, Monsanto isn’t the only corporation that does GMO research, marketing, and work, but they are the biggest.
One grower in Florida is already going ahead with GMO. Some of their tests appear promising, but it’s early yet. One group has created a bacteriophage that attacks C. Liberibacter. Another group inserted a gene from spinach that produces a protein that attacks invading bacteria (and no, the juice won’t taste like spinach.) This one appears to be the most promising, and trees bearing the spinach gene have already been planted in a test field far from other plants. They won’t bear fruit for a number of years yet. A third used a pig bacteria-fighting gene that appeared to be successful in adult trees. Another method simulated using a synthetic gene. And there’s an onion gene that’s being tested on tomatoes at Cornell University (psyllids prey on them, too.)
Whatever’s decided by the growers, it’ll have to be done soon. Floridian production of orange juice and other citrus products is already dropping, precipitously. Those predictions? They're not just hype. Shall we say goodbye to orange juice? Whither the orange?