Hillsborough Extension Garden Blog

Solutions you can use for your gardening problems.

Identifying Citrus Greening December 31, 2013

Filed under: Uncategorized — Hillsborough County Residential Horticulture @ 4:16 pm

A Hillsborough County resident contacts the Extension office, asking how to tell if her citrus trees are infected with citrus greening. She mentions over the past few years, her trees have declined and some of the leaves look similar to pictures she has seen online.

Citrus greening, also known as Huanglongbing (HLB) disease, is one of the more recent diseases affecting citrus trees. Confirmed in Florida in 2005, the disease has spread to all citrus producing counties in the state.

All citrus are susceptible to greening, and the disease is caused by the bacterium Candidatus Liberibacter spp. and the bacterium is spread by a tiny insect vector called the Asian citrus psyllid. When the Asian citrus psyllid feeds on infected citrus trees, it can pick up the disease-causing bacterium and move the disease from tree to tree.

This bacterial disease affects the vascular tissue of the plant (the phloem) and inhibits nutrient transport. When phloem transport is disrupted, signs such as twig dieback occur. Citrus greening causes smaller fruit, inferior fruit quality and taste, less fruit production, increased fruit drop and twig dieback.

To determine if citrus greening disease may be causing your tree to decline, please consider the following symptoms:

  • The early symptoms of citrus greening on leaves are vein yellowing and an asymmetrical “blotchy mottle.”
  • Trees may show twig dieback, causing productivity to decline within a few years.
  • Fruit are often few in number, small, may be lopsided with a curved central core and fail to color properly. You can often cut the fruit in half and notice the lopsided, central core.
  • Fruit drops prematurely from afflicted trees.
  • The fruit may contain aborted seeds and have a salty, bitter taste.
Asymmetrical fruit with lopsided central core and aborted seeds. Photo credit: JoAnn Hoffman

Asymmetrical fruit with lopsided central core and aborted seeds. Photo credit: JoAnn Hoffman

Leaf showing blotchy mottle. Photo credit: Mongi Zekri

Leaf showing blotchy mottle. Photo credit: Mongi Zekri

If your citrus trees are healthy, take care of them by following a routine fertilizer and irrigation schedule. Avoid planting and neglecting citrus trees in the landscape. If trees no longer produce fruit, homeowners must decide to remove them and whether or not to invest in replanting.

Florida oranges supply about 90% of the United States’ orange juice. Citrus greening impacts our lives because it reduces juice quality, decreases revenue and employment opportunities and affects Florida’s culture, as citrus trees and fruit are a sentimental, inherent part of Florida’s landscape and history. There is a lot we don’t know about this disease, but coordinated research efforts focused on psyllid control, tree nutrition, mapping genomes, biological control and disease-resistant trees may provide insight into this disease.

The UF/IFAS Extension Hillsborough County provides information about citrus greening and can assist you with symptom identification. Contact our office if you have questions about citrus greening or sample submission.

Nicole Pinson
Extension Agent – Urban Horticulture
Master Gardener Coordinator
UF/IFAS Extension Hillsborough County
5339 County Road 579
Seffner, FL 33584-3334
p: (813) 744-5519 X 54145



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