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

Abstract

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 > or =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.

Dispersal of adult Asian citrus psyllid, Diaphorina citri Kuwayama (Homoptera: Psyllidae), the vector of citrus greening disease, in artificial release experiments

“…We consider that D. citri not found in the experimental field were killed by natural enemies. Otherwise, in light of a report by Boina et al (2009) that adult D. citri may move 60-100 m within 3 days, it was possible that the adults had flown out of the experiment field; however, there was insufficient evidence to support this hypothesis.…”

“…Boina et al (2009) reported that a portion of D. citri moved bidirectionally between separated unmanaged and managed groves. We used field data in an attempt to perform a more quantitative evaluation of the relationship between the dispersal distance from the release point and arrival frequency.…”

Can early loss of affiliates explain the coextinction paradox? An example from Acacia-inhabiting psyllids (Hemiptera: Psylloidea)

“…Even if we assume that insects assess plant species abundance at a scale relative to the maximum distances they are capable of travelling, and that plant species use is also a function of the tendency for multiple generations to remain on the one host plant, these variables are not known for psyllids either. Psyllids in novel environments are capable of dispersing up to 100 m in 3 days (Boina et al 2009) or 10 km in 1 year (Center et al 2006) but comparable information is lacking for psyllids in more stable environments.…”

Asymptomatic spread of huanglongbing and implications for disease control

“…Hall and Hentz (23) used sticky traps to capture psyllid movement in and out of groves during arbitrary times in the year, with a peak time being in the spring. Boina et al (24) documented movement in both directions between managed and unmanaged groves. We assume that ∼30% of the initial psyllid population is infected.…”