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The dreaded citrus greening

Wayne Hobbs
Posted 1/4/17

GREEN COVE SPRINGS – Last week, we discussed the wonderful nature and popularity of the citrus trees of Florida. They are by far one of the most popular landscape plants but also one that I am …

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The dreaded citrus greening


Posted

GREEN COVE SPRINGS – Last week, we discussed the wonderful nature and popularity of the citrus trees of Florida. They are by far one of the most popular landscape plants but also one that I am asked about most frequently and with those questions, one topic seems to loom large in the worries of homeowners and the citrus industry as a whole.

Huanglongbing, commonly known as citrus greening disease, is present in our county and unfortunately is spreading throughout many of the trees throughout the state. The bacterial disease was first found in Florida in 2005 and has moved throughout much of the Southeast United States. Native to Asia, it is spread by the Asian Psyllid, which is a small winged insect that was discovered in Florida in 1998, possibly through illegally imported plant material.

Once infected, the disease will cause discoloration of the leaves, usually on a few branches before moving throughout the tree and roots. This results in a lower yield at first, with misshapen and discolored fruit, followed by the eventual death of the tree. In Central and South Florida, this disease has wiped out a high number of orchards and overall citrus yields continue to decline.

To diagnose greening, a laboratory test is needed, but some signs can be visible. The first and most common sign is the leaf discoloration. Areas of the leaf will be a lighter green or yellow than normal in a splotchy, asymmetrical pattern as seen in the image accompanying this article. Nutrient deficiencies are often mistaken for this disease but with those issues you will see a similar, mirrored pattern on both sides of the leaf rather than the more random patterning associated with greening.

Other signs of the disease can be seen in the fruit. Over time, you will notice a decline in yield and the fruit may become misshapen. When cutting open the fruit, you may see that one side of the fruit is larger than the other. Fruit can stay discolored on the tree as ripening occurs, retaining a green color, but this is different among different varieties and species of trees. The fruit is still safe for human consumption.

If you suspect your plant has greening, you can contact the UF/IFAS Clay County Extension Office by phone at (904) 284-6355 or by email through our website at http://www.clay.ifas.ufl.edu. Pictures of the tree including closeup shots of the leaves’ fruit can be very helpful and we can work to get potentially infected trees tested.

The worst news that comes with the disease is that, as of this moment, there is no treatment or cure other than to remove the affected tree to stop it from being a source of the disease. If another psyllid were to feed on that infected tree and then move to a healthy tree it will likely infect the new host. There is also no effective biological or chemical control at this time.

The best hope for controlling the disease and maintaining the citrus industry in Florida is through the development of resistant plants, which is currently being undertaken by the University of Florida, where advancements have been made and work continues to find a variety of citrus tree or citrus rootstock that can withstand infection.

If you have any more questions about citrus, any other landscape and garden topics, or need plant or pest materials identified, contact the University of Florida/IFAS Extension Office online at http://www.clay.ifas.ufl.edu, follow us on Facebook, or call by phone at (904) 284-6355.