Survey on citrus variegated chlorosis and citrus blight in Brazil
Citrus variegated chlorosis, a disease caused by Xylella fastidiosa (EPPO A1 quarantine pest) was first observed in Brazil in 1987. The disease was then spread by propagation material and sharpshooter vectors, and is now widely distributed in the citrus-growing areas of Brazil (see also EPPO RS 96/196). It is felt that citrus variegated chlorosis is potentially more devastating than citrus blight disease (EPPO A1 quarantine pest). It is observed that in Brazil, citrus blight (also called ‘declinio’) affects approximately 10 million trees a year. In Florida (US), it is estimated that 1 million trees are lost each year because of citrus blight. There have been controversial reports suggesting that citrus blight in Florida could be due to the Pierce’s disease strain of X. fastidiosa (it must be noted that Pierce’s disease has never been observed on grapevine in Brazil).
A survey was carried out in Brazil by using PCR techniques, on strains of X. fastidiosa present in citrus trees affected by citrus variegated chlorosis and citrus blight disease. Result showed that the X. fastidiosa strain identified as being the cause of citrus variegated chlorosis was consistently found with symptomatic citrus trees. In some cases, trees without symptoms were found infected with this strain. It can be noted that no other strain of X. fastidiosa was found on citrus. Finally during this survey, X. fastidiosa was never found associated with trees showing citrus blight symptoms.
Sources
Beretta, M.J.G.; Barthe, G.A.; Ceccardi, T.L.; Lee, R.F.; Derrick, K.S (1997) A survey for strains of Xylella fastidiosa in citrus affected by citrus variegated chlorosis and citrus blight in Brazil.
Plant Disease, 81(10), 1196-1198.