Understanding the effects of multiple sources of seasonality on the risk of pathogen spread to vineyards: vector pressure, natural infectivity, and host recovery

Abstract

Seasonality plays an important role in the dynamics of infectious disease. For vector-borne pathogens, the effects of seasonality may be manifested in the variability in vector abundance, vector infectiousness, and host-infection dynamics over the year. The relative importance of multiple sources of seasonality on the spread of a plant pathogen, Xylella fastidiosa, into vineyards was explored. Observed seasonal population densities of the primary leafhopper vector, Graphocephala atropunctata, from 8 years of surveys in northern California were incorporated into a model of primary spread to estimate the risk of pathogen infection under different scenarios regarding seasonality in vector natural infectivity (i.e. constant or increasing over the season) and grapevine recovery from infection (i.e. none or seasonal recovery). The extent to which local climatic conditions affect risk estimates via differences in vector abundance was investigated. Seasonal natural infectivity, seasonal recovery, and especially the combination, reduced (up to 8-fold on average) within-season and cumulative yearly estimates of pathogen spread. Estimated risk of infection also differed greatly among years due to large differences in vector abundance, with wet and moderate winter and spring conditions favouring higher G. atropunctata abundance. Seasonal variation of the pathogen-vector interaction may play an important role in the dynamics of disease in vineyards, reducing the potential prevalence from what it could be in their absence. Moreover, climate, by affecting sharpshooter leafhopper abundance or activity, may influence Pierce's disease dynamics.

Seasonal Patterns of Aster Leafhopper (Hemiptera: Cicadellidae) Abundance and Aster Yellows Phytoplasma Infectivity in Wisconsin Carrot Fields

“…However, the probability of inßux events occurring in May is lower than the probability of inßuxes occurring in mid to late-June. A similar phenology has been observed for Circulifer tenellus (Baker) (beet leafhopper), Psammotettix alienus (Dahib) (European grass-feeding leafhopper), and Graphocephala atropunctata (Signoret) (blue-green sharpshooter), all of which achieve peak abundance in June followed by population declines in late July and August (Lindblad and Areno 2002, Munyaneza et al 2010, Gruber and Daugherty 2012. It may be that these leafhoppers all overwinter, or diapause, in the same life stage (i.e., eggs) and have to develop through a similar number of instar stadia (i.e., four to Þve instars), leading to a reasonably synchronous emergence as adults among species.…”

Xylella fastidiosa: Insights into an Emerging Plant Pathogen

“…community composition, agricultural practices, and climate. Some, but not all, of these factors have been explicitly tested in X. fastidiosa diseases (e.g., 39,61,78).…”

Biology and ecology of the Flavescence dorée vector Scaphoideus titanus: a review

“…Like in other vector-borne diseases, the estimated risk of plant infection differs greatly depending on the vector population size between years and also as a function of local environmental conditions (Gruber and Daugherty 2013). Models to improve the understanding of the spatiotemporal population and pattern of infective vector dynamics were developed.…”