Citrus greening disease is a threat to the citrus industries in parts of Asia, Africa, South America and North America. Over the course of a few years, this systemic bacterial disease stunts the tree's growth resulting in reduced fruit output and quality. Initially thought to be a viral disease, it is now known to be caused by the bacterium, Candidatus Liberibacter asiaticus, and is vectored by the Asian citrus psyllid (ACP). While there is not yet a control for citrus greening, several practices including scouting, pest prevention and quarantining can all limit the incidence and spread of the disease.
- Vein yellowing & "blotchy mottle" - asymmetrical chlorosis that may resemble iron, zinc or manganese deficiencies.
- Poor root development - most evident on young trees or in nurseries.
- Twig dieback - generally indicates the disease has been present for more than a year.
- Lopsided fruit remaining green at the stylar (blossom) end.
- Premature fruit drop with a salty, bitter taste.
- Remove any infected plant material from the growing area.
- The disease can spread without the presence of Asian citrus psyllids.
- If Asian citrus psyllids are spotted, take proactive control measures.
- Traps using pheromone baits are helpful monitoring tools.
- Thyme Guard uses thyme oil extracts to boost the plant's natural defenses & has shown positive results controlling citrus greening (University of Florida Thyme Guard Report).
- Horticultural oils can be used to limit pest populations and kill psyllid eggs.
- Venerate XC has shown promise when used with Grandevo throughout the affected crop.
- Immediately notify your local agricultural extension if you believe citrus greening is present.
No known control for the disease is available; however, it is currently being researched. Focus control efforts on the Asian citrus psyllid and promote plant health with proper growing practices.