Survey of Citrus Huanglongbing （greening disease） on the Amami Islands. 3. Transition of diseased tree distribution after the second survey

Abstract

Citrus greening disease （CG） caused by 'Candidatus Liberibacter asiaticus' （Las） was investigated on Amamioshima, Tokunoshima, Okinoerabu and Yoron islands of Kagoshima in Southern Japan. Based on the distribution of infected trees in the second investigation from April 2006 to March 2009, citrus trees on four islands were categorized. A total of 143,782 citrus trees were investigated at 22,866 areas on four islands during the third investigation from April 2009 to March 2012. A total of 8,694 symptomatic trees at 6,569 areas were examined for Las infections by polymerase chain reaction （PCR）. As a result, 258 trees at 120 areas were confirmed to be infected. Infected trees and newly confirmed areas with infected trees in this survey were fewer than those in the second one on Tokunoshima and Yoron islands. The frequencies of uninfected/infected trees during this survey were calculated and compared with those during the second one. Odds ratios indicate that infected trees and newly confirmed areas with infected trees in this survey were fewer than those in the second one on Tokunoshima and Yoron islands. In order to detect latent infected trees, monitoring of CG is discussed.