Quantifying Dispersal of Diaphorina citri (Hemiptera: Psyllidae) by Immunomarking and Potential Impact of Unmanaged Groves on Commercial Citrus Management

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is an important pest of citrus. It is an efficient vector of three bacterial pathogens that are the presumptive causal agents of huanglongbing (HLB) or citrus greening disease. The movement patterns and dispersal capabilities of D. citri require study to better understand the spread of HLB and to improve management strategies for D. citri. A recently developed immunomarking technique that uses crude food proteins (chicken egg albumin, bovine casein, and soy protein) was evaluated for marking and tracking movement of D. citri in Florida citrus groves. In general, both egg and milk protein markers exhibited longer residual activity (35 d) than the soy protein marker (20 d) when applied to citrus leaves with a residual activity order of egg > milk > soy protein. However, residues of all three protein markers decreased with a simulated rain; this was more pronounced for soy protein than for egg and milk proteins. Temperature did not significantly affect acquisition of markers by adult D. citri. Egg, milk, and soy protein markers were detected on >90% of adult D. citri for up to 10, 10, and 5 d, respectively, after field application. Addition of tetrasodium ethylenediamine tetraacetic acid (water softener) and/or Silwet L-77 (wetting agent) to marker solutions did not affect longevity of detection. Each of the protein markers was detected on >= 80% of exposed D. citri for up to 30 d after direct application to adults. A field study was conducted to measure movement of D. citri between replicated pairs of 0.4 ha managed and unmanaged citrus plots separated by 60-100 m. Approximately 70% of captured D. citri were found marked 3 d after application of proteins in the field. Using two marker proteins, it was determined that D. citri moved bi-directionally between managed and unmanaged (abandoned) groves within 3 d with a greater number of D. citri adults moving from unmanaged into managed plots than from managed into unmanaged plots (net movement). These data indicate frequent movement by adult D. citri between groves and suggest that unmanaged groves may act as refuge sites for D citri, leading to reinfestation of nearby managed groves.