Photo 1. The "blotchy mottle" symptom of huanglongbing, yellow patches that are not the same size and position on both sides of the leaf.
Photo 2. Patches of yellow on a leaf showing the "blotchy mottle" symptom of huanglongbing; note that the patches are uneven, there are more on one side of the leaf than the other.
Photo 3. Symptoms of zinc deficiency for comparison with photos 1 and 2. Note that the yellowing is even throughout the leaf, not in patches which differ from left and right sides.
Photo 4. Late stage symptoms of huanglongbing: yellowing of most of the leaves, loss of leaves in the canopy and the start of dieback. Note that some of the fruit have green patches, hence the name of the disease "greening".
Citrus greening, citrus huanglongbing (greening) disease.
Candidatus Liberibacter asiaticus (Asian form), Candidatus Liberibacter africanus (African form), and Candidatus Liberibacter americanus (South American form). The three pathogens can only be distinguished by molecular tests. The abbreviation is HLB. The name 'huanglongbing' means 'yellow shoot disease'.
AUTHOR Grahame Jackson
Information from Briansky RH, Dewdney MM, Rogers ME (2014) Florida citrus pest management guide: huanglongbing (citrus greening). U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida. (http://edis.ifas.ufl.edu/cg086); CABI (2014) Crop Protection Compendium Citrus huanglongbing (greening) disease (http://www.cabi.org.cpc/); and information (and Photos 1&3) from Citrus diseases huanglongbing (HLB) (2013). USAD, UF. (http://idtools.org/id/citrus/diseases/factsheet.php?name=Huanglongbing+(HLB); and information (and Photo 2) Susan E Halbert In: Asian Citrus Psyllid and Huanglongbing Disease (2013) UCIPM Online. (http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74155.html). Photo 4 HD Catling, Bugwood.org. Photo 5 Jeffrey W Lotz, Florida Department of Agriculrture and Consumer Services, Bugwood.org.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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