Mike Irey is with Southern Gardens Citrus out of Florida and he has seen firsthand how devastating huanglongbing (HLB) can be to the citrus industry. Irey says there are a lot of products bombarding citrus growers that claim to help fight against the disease and figuring out which ones to use can be a difficult task.
Identification of HLB Disease
From the UC Integrated Pest Management website: In March 2012, huanglongbing was found in a citrus tree in Southern California, and this tree was destroyed to prevent the spread of this disease. Everyone’s assistance is needed to watch for additional infected trees. The disease may have already spread from this initial infection in Los Angeles in the bodies of psyllids to other citrus trees, or it may come into the state in an infected citrus tree or other host plant, illegally imported or smuggled into the state.
It could also arrive in the body of an infected psyllid that flies or rides on a plant into California from places such as Mexico where HLB and psyllids are found together. The tree that was found with HLB in Los Angeles is believed to have been infected through grafting a bud (taking plant tissue from one tree and inserting it into another to form a new branch) from another infected tree.
An early symptom of HLB in citrus is the yellowing of leaves on an individual limb or in one sector of a tree’s canopy. Leaves that turn yellow from HLB will show an asymmetrical pattern of blotchy yellowing or mottling of the leaf, with patches of green on one side of the leaf and yellow on the other side. Citrus leaves can yellow for many other reasons and often discolor from deficiencies of zinc or other nutrients. The pattern of yellowing caused by nutrient deficiencies typically occurs symmetrically between or along leaf veins.
As the disease progresses, the fruit size becomes smaller, and the juice turns bitter. The fruit might remain partially green, which is why the disease is also called citrus greening. The fruit becomes lopsided, has dark aborted seeds, and tends to drop prematurely.
Chronically infected trees are sparsely foliated with small leaves that point upward, and the trees have extensive twig and limb dieback. Eventually, the tree stops bearing fruit and dies. Fruit and tree health symptoms might not begin to appear until two to three years after the bacteria infect a tree.