Optimal Strategies for Interception, Detection, and Eradication in Plant Biosecurity

Diagnostic and Historical Surveys of Sweet Cherry (Prunus avium) Virus and Virus-Like Diseases in Oregon

There are over 35 known virus and virus-like diseases of sweet cherry (Prunus avium), some with potential to cause severe economic impact by reducing vegetative growth, vigor, or fruit quality. Oregon is the second-ranked state for sweet cherry production in the United States. Statewide surveys were conducted in Oregon sweet cherry orchards for virus and virus-like diversity and distribution. Orchards in key production regions with suspected virus disease symptoms were sampled. Virus-specific enzyme-linked immunosorbent assay, isothermal amplification, or quantitative real-time PCR were used to test for the presence of common or economically important sweet cherry pathogens, including cherry leaf roll virus (CLRV), little cherry virus 2 (LChV2), prune dwarf virus (PDV), prunus necrotic ringspot virus (PNRSV), tomato ringspot virus (ToRSV), and 'Candidatus Phytoplasma pruni'. CLRV, a new virus of sweet cherry in Oregon, was found associated with enation and dieback symptoms in The Dalles. Some viruses were found in new regions, which included Hood River (PDV, PNRSV, and ToRSV) and the Umpqua Valley (PDV and PNRSV). A subsequent survey was conducted in the Mid-Columbia production region for the presence of little cherry symptoms associated with little cherry and X-Diseases. All symptomatic samples from The Dalles and Mosier, OR, or Dallesport, WA, tested positive for 'Ca. P. pruni' but not LChV2. These findings provide a foundation for the current understanding and management of virus and virus-like diseases of sweet cherry in Oregon and context for further studies into these pathogens and their vectors.

Competition: A Missing Component of Fruit Fly (Diptera: Tephritidae) Risk Assessment and Planning

Tephritid fruit flies are internationally significant pests of horticulture. Because they are also highly invasive and of major quarantine concern, significant effort is placed in developing full or partial pest risk assessments (PRAs) for fruit flies, while large investments can be made for their control. Competition between fruit fly species, driven by the need to access and utilise fruit for larval development, has long been recognised by researchers as a fundamental component of fruit fly biology, but is entirely absent from the fruit fly PRA literature and appears not be considered in major initiative planning. First presenting a summary of the research data which documents fruit fly competition, this paper then identifies four major effects of fruit fly competition that could impact a PRA or large-scale initiative: (i) numerical reduction of an existing fruit fly pest species following competitive displacement by an invasive fruit fly; (ii) displacement of a less competitive fruit fly pest species in space, time or host; (iii) ecological resistance to fruit fly invasion in regions already with competitively dominant fruit fly species; and (iv) lesser-pest fruit fly resurgence following control of a competitively superior species. From these four major topics, six more detailed issues are identified, with each of these illustrated by hypothetical, but realistic biosecurity scenarios from Australia/New Zealand and Europe. The scenarios identify that the effects of fruit fly competition might both positively or negatively affect the predicted impacts of an invasive fruit fly or targeted fruit fly control initiative. Competition as a modifier of fruit fly risk needs to be recognised by policy makers and incorporated into fruit fly PRAs and major investment initiatives.

Host Species-Dependent Transmission of Tomato Leaf Curl New Delhi Virus-ES by Bemisia tabaci

The tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite, single-stranded begomovirus that was first identified in India in 1995 affecting solanaceous crops. A different strain, named ToLCNDV-ES, was introduced in Spain in 2012 and causes severe symptoms in zucchini crops. Virus transmission experiments with the whitefly Bemisia tabaci, were used to compare the transmission parameters in zucchini and tomato plants. The minimum acquisition access period and inoculation access period of ToLCNDV-ES transmission was similar in zucchini and tomato. However, the transmission efficiency was significantly higher in zucchini (96%) compared to tomato (2%). The maximum retention of the virus in the vector was 16 days. B. tabaci feeding on, or recently emerged from infected zucchini plants, accumulated more virus than those from infected tomato, as determined by real-time PCR. A total of 20% of B. tabaci that were recently emerged from infected zucchini, and none from infected tomato, were able to transmit the virus to virus-free zucchini. The results may explain the different incidences of ToLCNDV-ES in zucchini and tomato crops in Spain. But they are also relevant for ToLCNDV-ES management of crops and the role of the trade and transport of infected plant material, when small-sized immature stages of B. tabaci could be a source of infection.

Non-linear physiological responses to climate change: the case of Ceratitis capitata distribution and abundance in Europe

Understanding how climate change might influence the distribution and abundance of crop pests is fundamental for the development and the implementation of pest management strategies. Here we present and apply a modelling framework assessing the non-linear physiological responses of the life-history strategies of the Mediterranean fruit fly (Ceratitis capitata, Wiedemann) to temperature. The model is used to explore how climate change might influence the distribution and abundance of this pest in Europe. We estimated the change in the distribution, abundance and activity of this species under current (year 2020) and future (years 2030 and 2050) climatic scenarios. The effects of climate change on the distribution, abundance and activity of C. capitata are heterogeneous both in time and in space. A northward expansion of the species, an increase in the altitudinal limit marking the presence of the species, and an overall increase in population abundance is expected in areas that might become more suitable under a changing climate. On the contrary, stable or reduced population abundances can be expected in areas where climate change leads to equally suitable or less suitable conditions. This heterogeneity reflects the contribution of both spatial variability in the predicted climatic patterns and non-linearity in the responses of the species’ life-history strategies to temperature.

Risk Analysis: Celebrating the Accomplishments and Embracing Ongoing Challenges

As part of the celebration of the 40th anniversary of the Society for Risk Analysis and Risk Analysis: An International Journal, this essay reviews the 10 most important accomplishments of risk analysis from 1980 to 2010, outlines major accomplishments in three major categories from 2011 to 2019, discusses how editors circulate authors' accomplishments, and proposes 10 major risk-related challenges for 2020-2030. Authors conclude that the next decade will severely test the field of risk analysis.

A temperature-dependent physiologically based model for the invasive apple snail Pomacea canaliculata

In order to set priorities in management of costly and ecosystem-damaging species, policymakers and managers need accurate predictions not only about where a specific invader may establish but also about its potential abundance at different geographical scales. This is because density or biomass per unit area of an invasive species is a key predictor of the magnitude of environmental and economic impact in the invaded habitat. Here, we present a physiologically based demographic model describing and explaining the population dynamics of a widespread freshwater invader, the golden apple snail Pomacea canaliculata, which is causing severe environmental and economic impacts in invaded wetlands and rice fields in Southeastern Asia and has also been introduced to North America and Europe. The model is based on bio-demographic functions for mortality, development and fecundity rates that are driven by water temperature for the aquatic stages (juveniles and adults) and by air temperature for the aerial egg masses. Our model has been validated against data on the current distribution in South America and Japan, and produced consistent and realistic patterns of reproduction, growth, maturation and mortality under different scenarios in accordance to what is known from real P. canaliculata populations in different regions and climates. The model further shows that P. canaliculata will use two different reproductive strategies (semelparity and iteroparity) within the potential area of establishment, a plasticity that may explain the high invasiveness of this species across a wide range of habitats with different climates. Our results also suggest that densities, and thus the magnitude of environmental and agricultural damage, will be largely different in locations with distinct climatic regimes within the potential area of establishment. We suggest that physiologically based demographic modelling of invasive species will become a valuable tool for invasive species managers.