A generic risk‐based surveying method for invading plant pathogens

Abstract

Abstract. Invasive plant pathogens are increasing with international trade and travel, with damaging environmental and economic consequences. Recent examples include tree diseases such as sudden oak death in the Western United States and ash dieback in Europe. To control an invading pathogen it is crucial that newly infected sites are quickly detected so that measures can be implemented to control the epidemic. However, since sampling resources are often limited, not all locations can be inspected and locations must be prioritized for surveying. Existing approaches to achieve this are often species specific and rely on detailed data collection and parameterization, which is difficult, especially when new arrivals are unanticipated. Consequently regulatory sampling responses are often ad hoc and developed without due consideration of epidemiology, leading to the suboptimal deployment of expensive sampling resources. We introduce a flexible risk-based sampling method that is pathogen generic and enables available information to be utilized to develop epidemiologically informed sampling programs for virtually any biologically relevant plant pathogen. By targeting risk we aim to inform sampling schemes that identify high-impact locations that can be subsequently treated in order to reduce inoculum in the landscape. This ''damage limitation'' is often the initial management objective following the first discovery of a new invader. Risk at each location is determined by the product of the basic reproductive number (R 0 ), as a measure of local epidemic size, and the probability of infection. We illustrate how the risk estimates can be used to prioritize a survey by weighting a random sample so that the highest-risk locations have the highest probability of selection. We demonstrate and test the method using a high-quality spatially and temporally resolved data set on Huanglongbing disease (HLB) in Florida, USA. We show that even when available epidemiological information is relatively minimal, the method has strong predictive value and can result in highly effective targeted surveying plans.

Modeling when, where, and how to manage a forest epidemic, motivated by sudden oak death in California

“…Finding and mapping newly infected sites are expensive for an epidemic spreading through a heterogeneous host landscape in which access is limited by terrain, private ownership, and resources (8). Previous work has shown how to optimize the balance between detection and treatment to maximize the cost-effectiveness when there is a shared budget for detection and treatment, but has focused exclusively on simple theoretical models (37,38).…”

“…Routine detection and control of emerging pathogens of woodland trees, however, are prone to significant logistical and epidemiological constraints. Detection and reporting can be delayed by incomplete and infrequent sampling of large areas of susceptible hosts (8), with broad pathogen host ranges often increasing the area that must be surveyed. Infected sites may be inaccessible or under multiple ownership (9).…”

Modelling the spread and control of Xylella fastidiosa in the early stages of invasion in Apulia, Italy

“…For example, new techniques have been developed to guide surveillance strategies for emerging plant diseases (Parnell et al 2014) or in predicting their spread (see Chapman et al (2015) for a review). These techniques often rely on known parameter values, such as growth rates (Parnell et al 2015), to make future predictions.…”

Population dynamics of Pseudomonas savastanoi pv. phaseolicola in bean, throughout the epiphytic and pathogenic phases

“…Candidatus Liberibacter solanacearum, for example, an emerging disease in the United States, is being studied in depth, and integrated management strategies are being proposed (Lin & Gudmestad, 2013). Furthermore, new methods are being developed to facilitate the elaboration of surveys for newly reported pests (Parnell et al, 2014), and analyses on the possibility of outbreaks have been conducted to warn the authorities of the main risks from emerging threats (Janse, 2012). Lately, attention also has been paid to diseases categorized as reemerging.…”