Incidence of Huanglongbing and Citrus Rehabilitation in North Bali, Indonesia

Abstract

For many years, Tejakula mandarin, a popular local variety well adapted to the coastal region, was grown in the coastal plains of North Bali. Although Huanglongbing (HLB) was known to be present in Bali, it was thought to have been eradicated during programs in the early 1980s. From 1991 to 1993, up to 1 million Tejakula mandarin trees were planted in this region. Two citrus surveys for HLB were conducted in April 1996 and 1997. Based on symptomatology and the detection of the HLB liberibacter by PCR in leaf samples from over 200 trees, HLB was determined to be present throughout the coastal zones surveyed. Almost 100% of the Tejakula mandarin trees were affected and showed severe stunting. The causal agent was found to be “ Candidatus Liberibacter asiaticus”. Abundant populations of Diaphorina citri , the psyllid vector of HLB, were present and in certain orchards up to 15% of insects were HLB positive as shown by DNA hybridization of D. citri crush-blots. One of the major findings of our survey relates to the occurrence of HLB as a function of altitude. HLB was commonly present below an altitude of 650 m, however, HLB was rarely seen above 1,000 m. This distribution of HLB probably reflects that of D. citri.