Assessment of Citrus Greening Disease (Candidatus Liberibacter asiaticus) Risk in Benue State Citrus Orchards, North Central Nigeria

Citrus greening disease, caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus and transmitted by the Asian citrus psyllid Diaphorina citri, represents the most destructive citrus disease globally and a significant emerging phytosanitary risk for Nigeria's citrus industry. Benue State is among Nigeria's leading citrus-producing states, making assessment of greening disease risk a professional priority. This study conducted a structured phytosanitary risk assessment for citrus greening in Benue State orchards, combining psyllid population surveys, serological screening of symptomatic trees, and review of historical pathogen introduction pathways. Surveys across 48 citrus orchards in three local government areas identified D. citri populations in 58 percent of orchards sampled, establishing confirmed vector presence in the state. Polymerase chain reaction testing of 120 symptomatic citrus samples identified Candidatus Liberibacter-positive results in 11 percent of samples, representing the first confirmed report of the pathogen in Benue State orchards. Symptomatic trees exhibited characteristic blotchy mottle, lopsided fruit, and premature fruit drop. Risk factor analysis identified unregulated nursery-stock movement as the primary introduction pathway. The study recommends immediate quarantine measures restricting movement of citrus planting material into and within Benue State, establishment of a psyllid monitoring network, and investigation of biological control options for D. citri population management. Keywords: citrus greening, Candidatus Liberibacter, Diaphorina citri, Benue State, risk assessment.