Seasonal Patterns in the Frequency of Candidatus Liberibacter Asiaticus in Populations of Diaphorina citri (Hemiptera: Psyllidae) in Florida

Abstract

Candidatus Liberibacter asiaticus (CLas) is one of the putative causal agents of huanglongbing, which is a serious disease in citrus production. The pathogen is transmitted by Diaphorina citri Kuwayama (Hemiptera: Psyllidae). As an observational study, six groves in central Florida and one grove at the southern tip of Florida were sampled monthly from January 2008 through February 2012 (50 months). The collected psyllids were sorted by sex and abdominal color. Disease prevalence in adults peaked in November, with a minor peak in February. Gray/brown females had the highest prevalence, and blue/green individuals of either sex had the lowest prevalence. CLas prevalence in blue/green females was highly correlated with the prevalence in other sexes and colors. Thus, the underlying causes for seasonal fluctuations in prevalence operated in a similar fashion for all psyllids. The pattern was caused by larger nymphs displacing smaller ones from the optimal feeding sites and immunological robustness in different sex–color morphotypes. Alternative hypotheses were also considered. Improving our understanding of biological interactions and how to sample them will improve management decisions. We agree with other authors that psyllid management is critical year-round.

Grove-level analysis of titer and prevalence of “CandidatusLiberibacter asiaticus” andWolbachiainDiaphorina citri,vector of citrus Huanglongbing

“…Finally, a recent paper, published in 2023 by Ebert et al, surveyed multiple commercial sites in Florida. However, their samples were collected between 2008 and 2012, (Ebert et al 2023) making our study the latest published record of commercial psyllid vector capacity variability in Florida and perhaps the last one before the wide-spread adoption of injectable oxytetracycline (OTC) for HLB management in Florida. Now that direct injection of the OTC is becoming a wide-spread HLB management tactic in Florida, understanding the impact of OTC on CLas titer in psyllids will be important to understand if the use of OTC will indirectly lower vector competency in psyllid populations.…”