Measures for reducing primary infections in the integrated management of Huanglongbing in São Paulo citrus belt: technical and economic feasibility

Abstract

Huanglongbing (HLB), a disease mainly associated with the bacterium Candidatus Liberibacter asiaticus, transmitted by the Asian citrus psyllid Diaphorina citri, is present in all citrus production areas of Sao Paulo State. The disease causes severe sweet orange yield losses and fruit quality damages and endangers the sustainability and competitiveness of this important agribusiness generator of income and jobs in the State. Since there is no curative methods, the prevention of new infections is essential for controlling this disease. Effective control of secondary infections, arisen from the acquisition of bacteria in diseased trees and its transmission to healthy trees inside the orchard, has been achieved with constant removal of HLB-symptomatic trees and systematic vector control within the orchard. Frequent insecticide sprays break the psyllid life cycle (from egg to adult) and prevent the bacteria acquisition by adult psyllids on non-eliminated diseased trees, and, prevent the bacteria latency period within the psyllid to be completed in the case of bacteria acquisition by adult psyllid. However, primary infections, arisen from infectious psyllids those acquired the bacteria in external sources of inoculum and often disperse from these sources to the orchard searching for new shoots to feed and reproduce, are not completely avoided by these practices. Therefore, this project aims to evaluate the technical and economic feasibility of available measures to the growers, which could be integrated in order to reduce these primary infections. Outside the orchard, measures applied directly to control the primary inoculum source will be evaluated. In the orchard edge, up to 200 m from the orchard boundary, the region with the highest concentration of bacteria carrier migrant psyllids from neighboring areas, other measures will be evaluated to bar the primary dispersion into the orchard; prevent the primary inoculation of bacteria by psyllid, and preventing the vector access to the plant or its feeding on the plant. (AU)