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Fruit affected by Huanglongbing

Fruit affected by Huanglongbing (USDA)


Huanglongbing (HLB), also known as Citrus greening, has been confirmed in Trinidad for the first time. The disease, which was detected on leaves from a lime tree in the north of the island, can cause devastating yield loss for Citrus growers and is regarded as one of the most important threats to global commercial and sustainable citrus production. 
Huanglongbing, which means ‘yellow dragon disease’ starts with a yellow shoot on the Citrus tree. Then, as the disease progresses, the rest of the canopy gradually turns yellow and mottled. Severely infected trees have fewer leaves, extensive dieback and small misshapen fruits. The disease detected in Trinidad was caused by bacteria, Candidatus Liberibacter asiaticus, which can infect any species and variety of Citrus. These bacteria are carried by a vector, usually the Asian psyllid (Diaphorina citri), which carry the bacteria to other plants as they feed. Long distance spread of the disease can also be caused by movement of infected psyllids and plant material.
Adult Citrus Psyllid

Adult Citrus Psyllid (Public domain CCO)


There is no known cue for HLB so management of the disease usually focuses on preventing its spread by removing infected trees and controlling the vector. This can be done by increasing the number of natural enemies (e.g. spiders, lacewings, predatory mites and ladybirds), introducing parasitic wasps (e.g. Tamarixia radiata) or, in severe cases, spraying with a registered insecticide, such as imidacloprid.
Leaf samples from the infected lime tree in Trinidad were tested by the University of Florida, Plant Diagnostic Center (UF/IFAS) and confirmation of the disease has been published in an IPPC pest report, available here: https://www.ippc.int/en/countries/trinidad-and-tobago/pestreports/2017/06/detection-of-huanglongbing-or-citrus-greening-candidatus-liberibacter-asiaticus-in-trinidad/

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