Skip to main content
ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Plant Pathology Research » Research » Publications at this Location » Publication #309719
Title: Early-detection surveillance for an emerging plant pathogen: a rule of thumb to predict prevalence at first discovery

Author
item PARNELL, S - Rothamsted Research
item Gottwald, Timothy
item CUNNIFFE, N - University Of Cambridge
item CHAVES, V - University Of Cambridge
item VAN DEN BOSCH, F - Rothamsted Research

Submitted to: Proceedings of the Royal Society B
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2015
Publication Date: 9/3/2015
Citation: Parnell, S., Gottwald, T.R., Cunniffe, N.J., Chaves, V.A., Van Den Bosch, F. 2015. Early-detection surveillance for an emerging plant pathogen: a rule of thumb to predict prevalence at first discovery. Proceedings of the Royal Society B. 282:20151478.

Interpretive Summary: Emerging plant pathogens as well as other pests are an increasingly significant problem not only for agricultural commodities but also in conservation, forestry and relative to food security. Most often there is a reliance on human surveys to detect the pest/pathogen before it gets out of control. Unfortunately, in practice many epidemics are not discovered by such surveys until they are already at a high incidence (proportion of plants infected) and potentially beyond control. In this paper we demonstrate how we have derived and test a simple rule-of-thumb that allows us to estimate the incidence the disease will reach before it will be detected under normal circumstances. We demonstrate that this rule of thumb is a very good predictor and takes into account many of the complex variable associated with a broad collection of plant epidemics. Our work supports the view that, for the purposes of early warning surveillance, simple models can provide useful insights in apparently complex systems. The insight gained can inform decisions on surveillance resource allocation in plant health and has potential applicability to a broad array of invasive species in general.

Technical Abstract: Emerging plant pathogens are a significant problem in conservation, forestry and food security. Surveillance is often instigated in an attempt to detect an invading epidemic before it gets out of control. Yet in practice many epidemics are not discovered until already at a high incidence. This is partly due to a lack of quantitative understanding of how surveillance effort and the dynamics of an invading epidemic relate. In this paper we derive and test a simple rule-of-thumb approximation to determine, for any given surveillance program, the expected incidence an epidemic will have reached when first discovered, E(q*). We show that E(q*)=r/(N/') i.e. simply the rate of epidemic growth divided by the rate of sampling; where r is the epidemic growth rate, N is the sample size and ' is the time between sampling rounds. We demonstrate that this rule of thumb is robust to complex spatio-temporal epidemic models as well as data from real epidemics. Our work supports the view that, for the purposes of early warning surveillance, simple models can provide useful insights in apparently complex systems. The insight gained can inform decisions on surveillance resource allocation in plant health and has potential applicability to invasive species generally.