What is citrus HLB-greening?
Hunglongbing (HLB), also known as citrus greening or yellow dragon disease, has been reported to be one of the most serious diseases of citrus. Once a tree is infected, there is no cure for the disease and all citrus varieties are susceptible; regardless of rootstock. It is a bacterial disease that greatly reduces production, destroys the economic value of the fruit and kills trees. The HLB-bacteria multiplies within the phloem cells of the plant effectively clogging-up the phloem tubes. Phloem vessels carry organic nutrients such as sugars around to all areas of the plant. Without functioning phloem the trees will die. In areas of the world where HLB-greening is endemic citrus trees decline and die within a few years. The disease presents no threats to the health of people or animals.
What are the Symptoms of HLB-greening?
The most characteristic foliage symptoms are blotchy mottling of leaves and leaf yellowing that may appear on a single leaf, shoot, or branch. Symptoms can be easily confused with signs of micronutrient deficiencies. Other symptoms include twig dieback, poor flowering, and stunted growth. Fruit are small and misshapen. Symptoms are normally expressed from 6 months to 2 years after infection and young trees will be expected to die from 3 to 5 years after becoming infected. Older trees can take up to 8 to 12 years to die.
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How is HLB-greening spread?
HLB-greening is spread in Belize by an insect known as the Asian Citrus Psyllid, Diaphorina citri (confirmed to be present in Belize since 2005). The use of infected nursery plants can also be a significant source of the disease in the grove. Also, nursery plants can become infected through the use of infected budwood in plant preparation or through feeding of the psyllid on nursery plants. The psylllid transfers the HLB-greening bacteria from infected trees to healthy trees.