During the Fourth Annual Agriculture Research Conference jointly hosted by the National Agricultural Research and Extension Institute (NAREI) and the Ministry of Agriculture professionals in agriculture were told that Guyana’s citrus industry is not affected by the deadly citrus greening disease.

NAREI’s Research Scientist, Reynard Ward during his presentation highlighted the devastating impact of this disease on a country’s citrus industry. The disease which has no cure is spread by a vector and plants parts.

Citrus greening, also called huanglongbing or the yellow dragon disease, is a plant disease that destroys the production, economic value, and taste of fruits mainly from the citrus family. “The US which has a large citrus industry has seen a decline in billions of US dollars per year owing to this disease,” Ward said.

To date, it has spread to numerous countries in the Greater Caribbean region including:
Brazil, Venezuela, Jamaica, Cuba, Bahamas, Cayman Islands, Puerto Rico, St. Thomas and Belize. It is also distributed in the USA, Asia and the Middle East.

The causative agent is a bacterium called, Candidatus Liberacter. This organism can be
transmitted by the following means: (a) Through propagation of infected seeds and grafted cuttings; (b) By way of a vector, the Asian citrus psyllid (Diaphorina citri). This is a tiny insect (3 mm in length) that is mottled brown in colour. The adult feeds with its head down, almost touching the leaf, and the rest of its body elevated from the surface at an almost 45-degree angle with its tail end in the air.

Symptoms:

• Early symptoms include yellowing of only one limb or sector of the tree canopy,
• Followed by vein yellowing or a blotchy mottling of all or part of the leaf blade;
• Chronically infected trees display extensive twig and limb dieback, drop fruits prematurely and are sparsely foliated with small leaves that point upward;
• Fruits are frequently small, underdeveloped, and misshapen, with curved columella and aborted seeds;
• Fruits also tend to remain green at least in part, and colouring starts at the peduncle end;
• The juice is low in soluble solids, high in acid, and abnormally bitter, rendering the fruit inedible.

Control
Biological control using arthropods such as:
(a) Coccinellid predatory beetles;
(b) Hymenopterous parasites

Chemical treatment of nursery stock and new planting materials using systemic insecticides; if the rate of uptake and reactivity is slow, a broad-spectrum insecticide can be applied in conjunction for more immediate control.

Farm Sanitation
(a) Removing and destroying all known infected plant, even if they do not
show any symptoms;
(b) Collecting and testing suspected plants, in case it was grafted from the same source of infected materials;

Regulatory actions including prohibiting or restricting the import of citrus from diseased areas.