Q&A: Huanglongbing and the Asian Citrus Psyllid


HLB was recently found on a citrus tree in the City of Riverside. If you are a Riverside County resident with citrus trees, visit the Riverside County Agriculture Commissioner’s Office website (http://www.rivcoawm.org/) to see the latest news on HLB in Riverside and information for homeowners and growers. You can also see if you live in the quarantine area, which prohibits the sale of all host nursery stock and the movement of all host plants and fruits within the quarantine area, and applies to residents and commercial operations alike.

What is Huanglongbing (HLB) and why is it important?

Huanglongbing (HLB), also known as citrus greening disease or yellow shoot disease, is a very destructive bacterial disease of citrus and closely related plants. It is spread by psyllids and through grafting with infected budwood. Symptoms include yellow shoots, blotchy leaf mottle, small lopsided fruit and juice with bitter flavor. Diseased trees stop producing fruit and must be removed and destroyed to prevent further spread of the disease. HLB is a serious threat to all citrus in California. (Source: UC Riverside on the Riverside County Agriculture Commissioners website.) 

What does Huanglongbing and the Asian Citrus Psyllid look like?

HLB causes assymetrical blotchy mottling of leaves (in contrast to Zinc deficiency that causes symmetrical blotching).  Fruit from HLB-infected trees are small, lopsided, poorly colored, and contain aborted seeds. The juice from affected fruit is low in soluble solids, high in acids and abnormally bitter.  The fruit retains its green color at the navel end when mature, which is the reason for the name “citrus greening disease.”  The fruit is of no value because of poor size and quality. (Source: The UCR Center for Invasive Species Research)

See the flier produced by UC Riverside on the Riverside County Agriculture Commissioners website for images of HLB-infected trees and the Asian Citrus Psyllid.

Also see Californiacitrusthreat.org for more images and video.

What are my options as a homeowner for controlling HLB and ACP on my citrus trees?

The University of California Division of Agriculture and Natural Resources (UCANR) provides information on biological and insecticidal methods of control, and other resources on its website (Source: UCANR: http://ucanr.edu/sites/ACP/Homeowner_Options/)

What pesticides can I use to treat Asian Citrus Psyllid?

UCANR provides a listing of recommended pesticides at: http://ucanr.edu/sites/ACP/Homeowner_Options/Homeowner_Management/Insecticide_Treatments/

I have citrus trees on my property, what should I do?

 Inspect trees for the Asian Citrus Psyllid and Huanglongbing monthly, and whenever watering, spraying, pruning or tending trees. If you spot the pest or disease, call the California Department of Food and Agriculture (CDFA), at 800-491-1899. View the slideshow provided by the CDFA, at: http://californiacitrusthreat.org/pest-disease/ (Source: http://californiacitrusthreat.org/)

More tips:

  • When planting new citrus trees, only purchase the trees from reputable nurseries. Do not accept tree cuttings or budwood from friends or relatives.
  • After pruning or cutting down a citrus tree, dry out the green waste or double bag it to make sure that live psyllids won't ride into another region on the foliage.
  • Control ants in and near citrus trees with bait stations. Scientists have released natural enemies of ACP in Southern California to help keep the pest in check. However, ants will protect ACP from the natural enemies. Ants favor the presence of ACP because the psyllid produces honeydew, a food source for ants.
  • Learn more about the Asian citrus psyllid and huanglongbing disease by reading the detailed pest note on UC ANR's Statewide Integrated Pest Management website.
  • Assist in the control of ACP by supporting CDFA insecticide treatments of your citrus or treating the citrus yourself when psyllids are present.
  • Support the removal of HLB-infected trees. 

(Source: University of California Division of Agriculture and Natural Resources)

What is UC Riverside doing to combat HLB?

Building on many years of research efforts, experts in the University of California, Riverside’s College of Natural and Agricultural Sciences (CNAS) have been working with government and industry officials to address the disease and keep it from spreading.

Ongoing research efforts include breeding plants for resistance, developing molecular tools to combat this disease, new treatment programs using insecticides and bactericides, and early disease detection techniques. In the short term, UCR is developing techniques to increase citrus production and overall health to give the industry a boost. See more on research and experts at UCR Today. 

For more information, visit our helpful links page for HLB and ACP: http://cnas.ucr.edu/hlblinks.html








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