Diseases of citrus in the Mediterranean and Near East regions
FAO has recently published a book from Dr J.M. Bové, untitled “Virus and virus-like diseases of citrus in the Near East region”. This books gives descriptions of the major virus and virus-like diseases of citrus and then presents the phytosanitary situations observed during several missions made to Near East countries.
In addition, Dr Bové has presented a paper on major citrus diseases at the 10th Congress of the Mediterranean Phytopathological Union in which new information could be found. The EPPO Secretariat has tried to select from these sources the following new data on quarantine pests of citrus.
- Citrus tristeza closterovirus (EPPO A2 quarantine pest) is present in Somalia (new record according to the EPPO Secretariat) and in many Indian states for which we had previously no information: Andra Pradesh, Bihar, Haryana, Himachal Pradesh, Madhya Pradesh, Rajasthan, Sikkim, Uttar Pradesh, West Bengal.
A new detection method has been developed in Florida and Spain: the direct tissue blot immuno-assay (DTBIA) which is faster than ELISA, but with an equivalent sensitivity (Garnsey et al., 1993).
Toxoptera citricida (EPPO A1 quarantine pest, vector of tristeza) is also present in the following Indian states: Orissa and Punjab.
- Citrus greening bacterium (EPPO A1 quarantine pest) is present in Somalia (new record according to the EPPO Secretariat) and in many Indian states for which we had previously no information: Andra Pradesh, Bihar, Delhi, Gujarat, Himachal Pradesh, Jammu, Karnataka, Kerala, Madhya Pradesh, Orissa, Rajasthan, Tamil Nadu, Uttar Pradesh. In India, citrus greening bacterium and its vector Diaphorina citri (EPPO A1 quarantine pest) are present in all citrus-growing areas. Another vector, Trioza erytreae (EPPO A1 quarantine pest) is highly suspected in Somalia and is present in Ethiopia.
- Citrus ringspot (EU Annex II/A1) and citrus psorosis diseases are thought to be induced by different strains of the same virus (EPPO RS 95/203). The morphology of the virus particles observed is complex and suggests that the virus represents a new genus related to tenuivirus. The name spirovirus had first been suggested, but more recently the term ophiovirus has been proposed.
- Spiroplasma citri (EPPO A2 quarantine pest) is present in Somalia, Oman, Sudan and United Arab Emirates (new records according to the EPPO Secretariat). New data are also given for its vectors:
Neoaliturus haematoceps (EU Annex II/A2) is present in Cyprus, Egypt, Iraq and Saudi Arabia.
Neoaliturus tenellus occurs in Iran and Saudi Arabia.
- Hishimonus phycitis, the putative vector of lime witches broom phytoplasma was found in Oman (in 1991) and was constantly associated with lime trees, both healthy and diseased. It was also found in 1993 in United Arab Emirates (where lime witches broom phytoplasma is also present). Hishimonus phycitis is a well known insect species in India and Pakistan (where lime witches broom has not been reported).
- The presence of mal secco (Deuterophoma tracheiphila – EU Annexe II/A2) seems to be confirmed in the Italian and French riviera.
- As reported in EPPO RS 95/228, Xanthomonas axonopodis pv. citri (EPPO A1 quarantine pest) has been found again in Florida (US). In addition to this finding, American scientists have observed an interaction between citrus canker and Phyllocnistis citrella (Gottwald ; Graham, 1997). The citrus leaf miner can carry the bacterium on its body, and as it mines the leaves, numerous bacterial lesions develop along these mines.
Sources
Bové, J.M. (1995) Virus and virus-like diseases of citrus in the Near East region. FAO, Rome, 518 pp.
Bové, J.M.; Garnier, M. (1997) Major diseases and pathogens of citrus in the Mediterranean and Western Asia: today and tomorrow.
Proceedings of the 10th Congress of the Mediterranean Phytopathological Union, 1997-06-01/05, Montpellier (FR), 1-10.
Garnsey, S.M.; Permar, T.A.; Cambra, M.; Henderson, C.T. (1993) Direct tissue blot immunoassay (DTBIA) for detection of citrus tristeza virus (CTV). p 39-50.
In: Moreno, P.; de Graça, J.V.; Timmer, L.W. (Eds) Proceedings of the 12th Conference of the International Organization of Citrus Virology.
Gottwald, T.R.; Graham, J.H. (1997) An epidemiological analysis of the spread of citrus canker in Urban Miami, Florida, and synergistic interaction with the Asian citrus leaf miner.
In: Abstracts of the 5th International Congress of Citrus Nurserymen, Montpellier (FR), 1997-03-05-08.