Influence of HLB management on Diaphorina citri dispersal and disease spread to neighboring citrus areas

Abstract

Huanglongbing (HLB, Greening) is one of the most important citrus diseases worldwide. No curative methods are available for HLB and only preventive control strategies can reduce its damages and losses (HLB management). Those strategies have to be applied simultaneously and are: I) planting of pathogen-free nursery plants; II) frequent elimination of symptomatic trees (roguing), and III) vector control (Diaphorina citri). Their adoption is time and financially consuming and, by consequence, difficult to be applied by citrus growers. In addition, non-commercial citrus areas can be reservoirs of both pathogen and vector. Despite the eradication policy determined by state and federal Governments in Brazil, commercial and non-commercial citrus areas presenting HLB affected trees are very common. Those areas are sources of inoculum for HLB spread and put under risk areas where the HLB management is adopted. This is a current situation in citrus regions in the Americas (São Paulo and Paraná states, Brazil, and Florida State, USA). Our objective in the present study is to determine the influence of areas with no, or partial HLB management, on citrus orchards well managed. HLB-affected trees and D. citri populations will be estimated in neighboring citrus areas, with and without HLB management. For the well-managed orchards will be determined: I) the spatial and temporal dynamics of HLB affected trees, and II) the vector's population and distribution. Statistical analysis will be performed to establish sampling patterns for D. citri. In addition, the distance of influence between citrus areas with different HLB management will be estimated. An experimental area is under evaluation in Anhembi municipality in São Paulo. Four neighboring citrus areas with different HLB managements are in evaluation about the temporal and spatial HLB-affected trees and it´s a vector. Yellow sticky traps were located in twelve citrus plots inside those four areas to detect D. citri adults. Sampling procedures are been taken in citrus flushes to identify eggs and nymphs of D. citri. Adults and nymphs are evaluated by PCR to determine the presence of Ca. Liberibacter spp. Results will be used to compare local and regional HLB control strategies to maintain low incidences of HLB-affected trees. (AU)