Huanglongbing and the future of citrus in São Paulo state, Brazil

Abstract

Diaphorina citri, the Asian citrus psyllid and insectvector of huanglongbing (HLB) disease of citrus, has been reported in São Paulo State (SPS) in 1942. HLB and the associated bacteria (Candidatus Liberibacter asiaticus and Ca. L. americanus) were detected in 2004 and, immediately, Fundecitrus recommended HLB management by the classic three-pronged system (TPS): (i) insecticide control of the psyllid population, (ii) reduction of liberibacter inoculum by removal of symptomatic trees and (iii) use of healthy trees for resets. In 2012, eight years later, large farms in which a rigorous TPS has been practiced have an HLB incidence of less than 1% symptomatic trees a year and they account for a total area of ca. 200,000 ha. This surface can probably be doubled in the years to come. The successful HLB management by the TPS must be continued in SPS not only during the next 5 to 10 years, if not 10 to 15 years, required to develop HLB-resistant, genetically modified citrus (GMC) trees, but also afterwards, when GMC trees will hopefully be available. The low-HLB farms, with a high percentage of healthy trees, represent the "hard-core-orchards" on which the future of the SPS citrus industry will be constructed. They offer appropriate conditions for hosting not only the GMC trees (option 1), but also for the uninterrupted production of regular, non-GMC trees in spite of HLB (option 2).