Influence of limiting and regulating factors on populations of Asian citrus psyllid and the risk of insect and disease outbreaks

Authors: UDELL, BRADLEY - University Of Florida; MONZO, CESAR - University Of Florida; Paris, Thomson; Allan, Sandra - Sandy; STANSLY, PHILIP - University Of Florida

Submitted to: Annals of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2016
Publication Date: 7/1/2017
Citation: Udell, B.J., Monzo, C., Paris, T.M., Allan, S.A., Stansly, P.A. 2017. Influence of limiting and regulating factors on populations of Asian citrus psyllid and the risk of insect and disease outbreaks. Annals of Applied Biology. 171(1):70-88.
DOI: https://doi.org/10.1111/aab.12349

Interpretive Summary: The Asian citrus psyllid is the insect vector transmitting the devastating citrus disease (Huanglongbing). Huanglongbing has caused billions of dollars in damage to the citrus growers and industry in Florida since its detection in 2005. Critical to prediction of disease spread is a better understanding of the ecological factors that contribute to population increase and dispersal of the insect vector. In this study, conducted by scientists at the USDA, Agricultural Research Service, Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida, seasonal and distribution data of Asian citrus psyllids from two Florida citrus groves were analyzed to develop models describing the role of ecological factors. A major factor in psyllid dispersal, which in turn would impact area-wide transmission of Huanglongbing, was intraspecific competition for resources amongst the psyllids. This study underscores the critical role of effective monitoring and management of Asian citrus psyllid densities to control and reduce dispersal of psyllids and the associated disease, Huanglongbing, to uninfected citrus plantings.

Technical Abstract: Data from long term monitoring programs in two Florida citrus groves were used to assess Asian citrus psyllid demography and population ecology, which is needed to implement more effective management strategies for huanglongbing. We describe and interpret seasonal patterns and correlations between Asian citrus psyllid density estimates and a suite of environmental and community indicators previously shown to influence Asian citrus psyllid demography. Next, we evaluate evidence for spatial clustering and density dependent recruitment of psyllid in an extreme and violent outbreak event using Taylor’s Power law analysis and by fitting a stochastic Beverton-Holt recruitment model, using a hidden Markov approach. We find strong evidence for density dependent recruitment and spatial clustering, which should be taken into account for future modeling work can as it can greatly influence how psyllid populations grow and huanglongbing is transmitted. Additionally, observations of psyllid density in space and time, along with the estimated parameters from the Beverton-Holt model suggest, that intraspecific competition for resources may initiate a widespread dispersal process, thus affecting area wide huanglongbing transmission. Finally, dynamic patterns in the spatial dispersion index of adult psyllid were synthesized with the density dynamics analysis and the ecological literature to infer movement patterns of Asian citrus psyllid during the outbreak event. All results were interpreted in the context of Asian citrus psyllid ecology and management.