Citrus Greening: Biodiversity Crisis Plays Out In Your Own Backyard

Characteristic signs of Citrus Greening;  Yellowing leaves and fruit.

Across Central Florida, in most any backyard, you don't have to look hard to find diseased citrus trees that were once bountiful with fruit and ubiquitous around this region.  Citrus Greening (Candidatus Liberibacter asiaticus)  is one of the most serious citrus plant diseases in the world.  It is also known as Huanglongbing (HLB) or yellow dragon disease.  And, as most Floridians have learned, once a tree is infected, there is no cure.

 Follow Phillip

@majikphil

History of Citrus Greening in Florida

Citrus Greening was first confirmed in Miami, Florida in 2005 and the disease spread rapidly, creeping up the Florida peninsula. By June 2006, twelve counties in Florida were confirmed to be afflicted with the disease. Today, a reported 80% of orange trees in Florida are now affected and it is estimated by the end of the growing season, nearly every orange growing region in the U.S. will be impacted by the disease.

A Blue Ash Tree in Kentucky.
As Blue Ash trees grow old the central truck often dies and growth transfers to secondary limbs.

Similarly, wander into the woods in other places in the eastern United States and you’re likely to come across a towering trunk with sandy-colored, diamond-shaped ridges rising to bare forking branches and little holes peppering the bark, signaling where small, green beetles have crawled out and flown away after doing their dirty work. This decaying monument is — or rather, was — an ash tree. Its kind will not be back in your lifetime, perhaps ever.

If you live in the other half of the country, just wait a few years. The emerald ash borer is coming for your trees, too.

UN Report:  Nature's Dangerous Decline 'Unprecedented'; Species Extinction Rates 'Accelerating'

A damaged tree will continue to try and grow and make fruit, with little success.

Leaves from damaged Florida citrus trees

Humans are setting in motion a mass extinction of life, only the sixth in Earth’s 4.5 billion-year history. A recent United Nations report put this in stark numerical terms: As many as 1 million plant and animal species are at risk of annihilation. Such an astronomical figure, while intended to impress, can actually make the threat hard to relate to. Too often we view the global biodiversity crisis as remote or abstract, involving the disappearance of exotic, charismatic megafauna such as tigers and elephants, or obscure species most of us don’t recognize to begin with.

Citrus Greening came to Florida likely on an airliner or container ship bringing goods and people from Asia. Citrus greening is spread by a disease-infected insect, the Asian citrus psyllid (Diaphorina citri Kuwayama or ACP), and has put the future of America's citrus at risk. Infected trees produce fruits that are green, misshapen and bitter, unsuitable for sale as fresh fruit or for juice. Most infected trees die within a few years.

The citrus greening bacterium and the Asian citrus psyllid spread on infected citrus plants and citrus plant material. Plants and material can spread the infection even if no psyllids are visible. Commercial citrus fruit, which is typically graded, washed, brushed and cleaned, is not known to spread the disease.

Tangerine seem to be more immune to the effects of citrus greening but produce very small fruit with thicker rinds after infection.

The crisis isn’t remote, or abstract. Florida's orange trees and Ash trees across North America demonstrate that real, visible and consequential ecological catastrophes are playing out all around us.

Burning Florida Orange Trees is one way to control the spread of Citrus Greening.

But in 2017, in an announcement that received virtually no coverage in the United States, the International Union for the Conservation of Nature, which keeps track of threatened species, declared five American ash tree species — white ash, green ash, blue ash, black ash and pumpkin ash — critically endangered, the last step before total extinction. The rarer Carolina ash also was designated endangered.

Ash Borer holes in a tree in Kentucky.

Six species are in mortal peril, and 10 others are infested, because of one tiny beetle that arrived in the United States about 20 years ago, probably on shipping pallets. The ash’s 40-million-year run on our continent may have been doomed by this most mundane of events in the era of global trade, noticed by no one.

History of Citrus Greening Globally

Florida's dying citrus trees, realistically they never belonged in Florida anyway. Christopher Columbus brought the first citrus to the New World in 1493. The early Spanish explorers, probably Ponce de Leon, planted the first orange trees around St. Augustine, Florida, sometime between 1513 and 1565. The heritage left behind in citrus was destined to grow into industries worth billions of dollars.  So if it dies out it would be devastating financially for a few, but perhaps it was meant to be.  Maybe Citrus Greening was just nature's way of putting things back the way they were.  

The thick rind of Citrus Greening-damaged fruit.

One of our few remaining trees orange trees in Volusia County continues to bloom and try to make new growth, but it is obviously suffering.

But Citrus Greening doesn't only affect your backyard citrus trees.  Also threatened are a long list of other cousins including Chinese box-orange, Curry leaf, Finger lime, Grapefruit, Key lime, Kumquat, Lemon, Lime, Limeberry, Mandarine orange, Mock orange, Orange, Orange jasmine, Pomelo, Sour orange, Sweet orange, Tangerine,  and Trifoliate orange, to name a few.

And the Blue Ash of Kentucky may not be the only trees threatened.  What happens when the next invader, perhaps a bug that kills oak trees, wanders off a container ship near you?  It is a crisis unfolding in real time in your own backyard.

Sky Rojo's Miguel Ángel Silvestre

Sky Rojo Renewed for 2nd Season

Sky Rojo, the blockbuster recently renewed for a 2nd season on Netflix (coming July 23, 2021) by Álex Pina and Esther Martínez Lobato , creators of La casa de papel , tells the story of three prostitutes who escape from their pimp. The ones who cannot escape are Pina and Lobato, who turn each slap, each humiliation and each threat into a spectacle. "I'm going to cut off your arms and legs and leave only the holes," they say at one point.