Citrus greening huanglongbing (African) - Candidatus Liberibacter africanus
EEffective: August 18, 2010 - December 31, 2011
Resources:
Pest Tracker
Screening Aids:
| Huanglongbing - Citrus Greening - (HLB) Disease Symptoms |
Taxonomic Position:
Rhizobiales : Rhizobiaceae
Pest Type:
Bacteria
Pest Code (NAPIS):
FGCOLQC
| No manual – See Host Matrix |
These Approved Methods are appropriate for:
Pest is vectored by:
African citrus psyllid (Trioza erytreae), Asian citrus psyllid (Diaphorina citri)
Asian citrus psyllid is present in the United States. The Asian citrus psyllid has been detected in Alabama, Arizona, California, Florida, Georgia, Guam, Hawaii, Louisiana, Mississippi, Puerto Rico, South Carolina, Texas, U.S. Virgin Islands, and Mexico.
Survey
Approved Method(s):
| Method | Instructions | NAPIS Survey Method |
|---|
Signs:
No specific signs are present.
Symptoms:
Blotchy mottle on fully hardened off leaves located in the interior of the canopy, behind new growth; yellow shoots, mottling of leaves, small misshapen fruit that are sour to bitter in taste.
Key Diagnostics
ID/Diagnostic: Molecular
Molecular: All medium-high suspect level leaf and stem samples (based on symptoms) should be sent for molecular confirmation (PCR).
PPQ certified analysts in accredited labs should conduct either the validated conventional or real-time PCR assays (Li et al., 2006, Li et al., 2007).
Work instructions for these assays are available.
PPQ certified analysts in accredited labs should conduct either the validated conventional or real-time PCR assays (Li et al., 2006, Li et al., 2007).
Work instructions for these assays are available.
Mistaken Identities:
Citrus stubborn disease (Spiroplasma citri), citrus tristeza closterovirus (CTV), Phytophthora infection, citrus blight, and certain nutrient deficiencies (zinc).
In Progress / Literature-based Diagnostics:
Grafting: Susceptible seedling graft inoculation has been used but is extremely time-intensive due to the lengthy period necessary to observe symptoms (not recommended for CAPS).
Sechler et al. (2009) describe a culture medium that can culture Ca. L. asiaticus, Ca. L. africanus, and Ca. L. americanus.
Sechler et al. (2009) describe a culture medium that can culture Ca. L. asiaticus, Ca. L. africanus, and Ca. L. americanus.
Notes:
Iodine staining of suspect tissue has shown some promise for preliminary screening in the field.
Due to the rate of false negatives, this method should not be used in areas where HLB is not known to occur, but may have use in areas where HLB is prevalent to identify infected trees (this method has not been validated by PPQ).
Contact Renee DeVries ((301) 504-7100 x225 - renee.devries@aphis.usda.gov) for the most up-to-date work instructions.
Due to the rate of false negatives, this method should not be used in areas where HLB is not known to occur, but may have use in areas where HLB is prevalent to identify infected trees (this method has not been validated by PPQ).
Contact Renee DeVries ((301) 504-7100 x225 - renee.devries@aphis.usda.gov) for the most up-to-date work instructions.
References
- Floyd, J. and Krass, C. 2006. New Pest Response Guidelines: Citrus Greening Disease. USDA-APHIS-PPQ-Emergency and Domestic Programs, Riverdale, Maryland.
- Li, W., Hartung, J. S., and Levy, L. 2006. Quantitative real-time PCR for detection and identification of Candidatus Liberibacter species associated with citrus huanglongbing. Journal of Microbiological Methods 66: 104-115.
- Li, W., Hartung, J. S., and Levy, L. 2007. Evaluation of DNA amplification methods for improved detection of Candidatus Liberibacter species associated with citrus huanglongbing. Plant Dis. 91: 51-58.
- Sechler, A., Schuenzel, E.L., Cooke, P., Donnua, S., Thaveechai, N., Postnikova, E., Stone, A.L., Schneider, W.L., Damsteegt, V.D., and Schaad, N.W. 2009. Cultivation of Candidatus Liberibacter asiaticus, Ca. L. africanus, and Ca. L. americanus associated with huanglongbing. Phytopathology 99: 480-486.