Uncurable disease poses major threat to citrus crops

An orange tree showing early signs of infection with huanglongbing, AKA citrus greening. Photo by Division of Plant Industry, Florida Department of Agriculture and Consumer Services

Lizette Alvarez recently reported how a disease afflicting citrus trees around the world is threatening the Florida orange juice industry. She describes in The New York Times that

Although the disease, citrus greening, was first spotted in Florida in 2005, this year’s losses from it are by far the most extensive. While the bacteria, which causes fruit to turn bitter and drop from the trees when still unripe, affects all citrus fruits, it has been most devastating to oranges, the largest crop. So many have been affected that the United States Department of Agriculture has downgraded its crop estimates five months in a row, an extraordinary move, analysts said….

The disease, which can lie dormant for two to five years, is spread by an insect no larger than the head of a pin, the Asian citrus psyllid. It snacks on citrus trees, depositing bacteria that gradually starves trees of nutrients. Psyllids fly from tree to tree, leaving a trail of infection.

Concerted efforts by growers and millions of dollars spent on research to fight the disease have so far failed, growers and scientists said. The situation was worsened this season by an unusual weather pattern, including a dry winter, growers said.

Find the entirety of Alvarez’s informative piece here. For more, see the USDA’s Save Our Citrus website along with TexasCitrusGreening.org. Also, check out this Naples News column from University of Florida extension agent Doug Caldwell. He writes,

Since 2006, citrus greening has cost Florida’s economy an estimated $3.63 billion in lost revenues and 6,611 jobs by reducing orange juice production, according to a new study from the University of Florida’s Institute of Food and Agricultural Sciences.

It affects fruit ripening, lowers fruit production and ruins the taste of the affected fruit on any given tree.

Professor Phil Stansly, UF/IFAS, Immokalee Research Center, said that most affected fruits drop, and what is left looks and tastes normal. The symptoms are difficult to distinguish from several other diseases and nutrient deficiencies.

Growers, governments, and companies in the orange juice business (like Coca-Cola, which owns the Simply and Minute Maid brands) across the country are desperately searching for a solution. In the meantime, Caldwell writes that “The citrus grove management strategy for citrus greening disease is a two-pronged attack: First, control the vector and second, reduce stress factors, such as poor nutrition and drought.” Alvarez notes that “Baby citrus trees must now be raised in greenhouses before they can be transplanted. And most growers douse their groves with a more powerful cocktail of nutrients and spray insecticide more frequently, which has helped slow the disease’s progress.”

Caldwell has some treatment suggestions for the homeowner with citrus trees in the yard, but concludes with these thoughts:

Because I won’t make the nutrient and insect control [i.e., pesticide] applications, to achieve my dream of fresh honeybell orange juice from the backyard, I may need to look at my citrus trees as short-timers, maybe only lasting seven to eight years. I might replant a new citrus tree every five to 10 years to replace the declining trees.

We should plant other fruit that will grow in our unique subtropical climate, whether it is low-chill peaches or plums or papayas for that breakfast smoothie. See more about alternative fruit choices at trec.ifas.ufl.edu/fruitscapes.

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