Many unreported crop pests and pathogens are probably already present

Invasive species threaten global biodiversity, food security and ecosystem function. Such incursions present challenges to agriculture where invasive species cause significant crop damage and require major economic investment to control production losses. Pest risk analysis (PRA) is key to prioritize agricultural biosecurity efforts, but is hampered by incomplete knowledge of current crop pest and pathogen distributions. Here, we develop predictive models of current pest distributions and test these models using new observations at subnational resolution. We apply generalized linear models (GLM) to estimate presence probabilities for 1,739 crop pests in the CABI pest distribution database. We test model predictions for 100 unobserved pest occurrences in the People's Republic of China (PRC), against observations of these pests abstracted from the Chinese literature. This resource has hitherto been omitted from databases on global pest distributions. Finally, we predict occurrences of all unobserved pests globally. Presence probability increases with host presence, presence in neighbouring regions, per capita GDP and global prevalence. Presence probability decreases with mean distance from coast and known host number per pest. The models are good predictors of pest presence in provinces of the PRC, with area under the ROC curve (AUC) values of 0.75–0.76. Large numbers of currently unobserved, but probably present pests (defined here as unreported pests with a predicted presence probability >0.75), are predicted in China, India, southern Brazil and some countries of the former USSR. We show that GLMs can predict presences of pseudoabsent pests at subnational resolution. The Chinese literature has been largely inaccessible to Western academia but contains important information that can support PRA. Prior studies have often assumed that unreported pests in a global distribution database represent a true absence. Our analysis provides a method for quantifying pseudoabsences to enable improved PRA and species distribution modelling.     

Downscaling Pest Risk Analyses: Identifying Current and Future Potentially Suitable Habitats for Parthenium hysterophorus with Particular Reference to Europe and North Africa

Pest Risk Assessments (PRAs) routinely employ climatic niche models to identify endangered areas. Typically, these models consider only climatic factors, ignoring the ‘Swiss Cheese’ nature of species ranges due to the interplay of climatic and habitat factors. As part of a PRA conducted for the European and Mediterranean Plant Protection Organization, we developed a climatic niche model for Parthenium hysterophorus, explicitly including the effects of irrigation where it was known to be practiced. We then downscaled the climatic risk model using two different methods to identify the suitable habitat types: expert opinion (following the EPPO PRA guidelines) and inferred from the global spatial distribution. The PRA revealed a substantial risk to the EPPO region and Central and Western Africa, highlighting the desirability of avoiding an invasion by P. hysterophorus. We also consider the effects of climate change on the modelled risks. The climate change scenario indicated the risk of substantial further spread of P. hysterophorus in temperate northern hemisphere regions (North America, Europe and the northern Middle East), and also high elevation equatorial regions (Western Brazil, Central Africa, and South East Asia) if minimum temperatures increase substantially. Downscaling the climate model using habitat factors resulted in substantial (approximately 22–53%) reductions in the areas estimated to be endangered. Applying expert assessments as to suitable habitat classes resulted in the greatest reduction in the estimated endangered area, whereas inferring suitable habitats factors from distribution data identified more land use classes and a larger endangered area. Despite some scaling issues with using a globally conformal Land Use Systems dataset, the inferential downscaling method shows promise as a routine addition to the PRA toolkit, as either a direct model component, or simply as a means of better informing an expert assessment of the suitable habitat types.     

A Qualitative Analysis of the Pathway Pest Risks Associated with Export of Pineapple,Ananas comosus from the Southwest Nigeria to the USA.

This study investigated the diversity and risk status of the pests associated with pineapple fruit trade from Nigeria to the U.S.A. in a commodity-initiated Qualitative Pest Risk Assessment as required under the Sanitary and Phytosanitary agreement of member nations of the World Trade Organization. The study validated in the field as necessary, all fruit pests of pineapple, Ananas comosus in the southwest Nigeria that have potential to follow the risk pathway from the farm to the port of exit. Twenty four pests, comprising 18 species of insects, 5 fungi and 1 bacterium were identified. Among these, one insect — Zonocerus variegatus was identified as a quarantine pest of pineapple with potential to follow the pathway to the pest risk areas in the U.S.A. The likelihood of introduction based on climatic conditions matching the pest etiology and host biotics is medium. The climatic requirement of the pest is compared with those of the pest risk areas in the USA such as Georgia, Texas, Florida, California, and Alabama. The pest lays its eggs usually in soil but could be hidden in the leaf bract or scale on the pineapple fruit surface. The egg undergoes 6-9 months of diapause, depending on the environment. The infestive nymphs and adults are relatively large sized. The overall consequence of introduction is high but the risk of this pest following the pathway is rated medium. The mitigation in place in Nigeria such as pre-shipment inspection, cleaning and fumigation at the port of exit appears adequate but could still be improved to completely remove the likelihood of introduction. Gamma-irradiation which is likely to become available in Nigeria has the potential to remove totally the risk of introduction of this pest to the USA.     

Estimation of the probability of insect pest introduction through imported commodities

A quantitative risk assessment is needed for each quarantine pest insect to ensure quarantine security without sacrificing the transparency of international trade. The probability of introduction, which is defined as the probability that one or more reproductive individuals of a pest insect species pass the port, is one of the basic components determining the risk of pest invasion. The probability depends on two biological characteristics of pests: mode of reproduction and spatial distribution of insects per host plant. In this article, the probability of introduction was calculated for each of the following four categories: (1) bisexual, gregarious pests; (2) bisexual, solitary pests; (3) parthenogenetic, gregarious pests; and (4) parthenogenetic, solitary pests. Then, equations were derived to predict the effects of two prevention practices conducted before export: disinfestation treatment and the subsequent export sampling inspection of consignments. These equations also enable estimation of the probability of introduction under natural mortality, which thus can be used in place of the criterion of Maximum Pest Limit (MPL). The method was applied to the Mexican fruit fly Anastrepha ludens (Loew), as an example. The contour graph of the probability of introduction indicated the optimal combination of the intensity of two prevention practices that ensures a given security level. Existence of an antagonistic interaction was also indicated between the disinfestation treatment and the subsequent sampling inspection. Received: January 22, 1999 / Accepted: September 6, 1999     

广东省中山市2种红树林有害生物风险分析及防控策略

【目的】了解红树林有害生物风险及其防控,维护红树林健康生长,发挥红树林的生态功能。【方法】2018—2019年,连续2年对广东省中山市红树林有害生物种类进行系统调查监测,并对薇甘菊和星天牛2种有害生物在中山市的分布状况、定殖和扩散的可能性、潜在危害性、受害对象的重要性、防控难度等进行分析,结合红树林的生态效益,参照国际有害生物风险性分析方法对两者在中山市红树林的危害风险性进行综合分析评估。【结果】调查发现,中山市红树林主要有害生物有23种,其中薇甘菊、星天牛最为严重,评估风险性R值分别为1.63和1.61,属中度危险的林业有害生物。【结论】薇甘菊和星天牛目前仅在中山市红树林局部地区发生危害,但具有明显扩散蔓延趋势,应该建立以应急除治、生物防治、生态修复等多种技术相结合的生态控制技术体系。     

地中海实蝇与植物检疫

地中海实蝇Ceratitis capitata (Wiedemann)是国际上十分重要的检疫性害虫,也是我国植物检疫工作中重要防御的检疫性害虫之一,近年来,从我国口岸检疫中共截获地中海实蝇12次。这充分表明了其潜在的危险性。为此,我国采取了一系列严格的检疫措施,有效地防止地中海实蝇传入。同时,为适应改革开放和国际贸易的发展,对检疫政策进行了调整,积极开展对水果、蔬菜的有害生物风险分析(PRA)研究工作,根据国际标准,划定非疫区范围,使植物检疫对贸易的不利影响降到最低限度,以促进水果、蔬菜进出口贸易的发展。     

近10年外来入侵昆虫风险分析的研究现状及主要进展

随着经济全球化的加速发展,外来入侵昆虫对世界各国农林业、生态环境、社会经济和人类健康造成的影响日趋严重。近10年来,关于外来入侵昆虫风险分析的相关研究备受重视,发展迅速;在研究对象类别中,鞘翅目昆虫居多,占所有入侵昆虫的32.21%,其次为双翅目和膜翅目,最小的为缨翅目,仅占1.44%。风险分析主要包括入侵途径、适生范围及风险等级、传播扩散、经济和生态影响等层面;其中以适生性风险分析研究最多,占43.41%。深入开展入侵昆虫的风险分析,对防范和阻截其传入、扩散和蔓延具有重要的理论意义和应用价值。     

台州口岸进境近海小型国际航行船舶携带有害生物疫情调查

【目的】国际航行船舶可携带多种植物疫情,造成有害生物入侵。分析进境近海小型国际航行船舶携带有害生物疫情,能够为对该类船舶开展针对性检疫查验提供依据。【方法】对台州口岸进境小型国际航行船舶的概况、食品舱卫生状况和携带有害生物种类、来源进行调查和数据分析。【结果】2015—2016年调查了3193艘次船舶,共截获有害生物686种次,其中87.5%是昆虫类,截获比例最高时期为6—8月,55.9%的有害生物在干货类食品中截获,食品舱卫生差的船舶中有害生物检出比率为36.1%。【结论】进境近海小型国际航行携带有害生物情况严重,有害生物的发生具明显的季节性,食品舱卫生状况与有害生物携带风险密切相关,应采取有效的检疫措施。     

Interspecies interference and monitoring duration affect detection rates in chew cards

Pest monitoring methods should provide unbiased accurate estimates of pest densities and locations, while also minimizing time‐in‐field and costs. Recent pest mammal monitoring studies have found that chew cards are more effective than conventional mammal monitoring methods, but little experimental work has been done to determine optimal experimental duration or quantify the risks of saturation by one species biasing detections of other species. Here, we used chew cards in three sites within Awarua wetland (Southland, New Zealand) to investigate the optimal amount of time required to detect targeted pest species (rats, possums and mice), and to examine the potential of rats and possums to bias detection rates of other species. We found depressed detections of possums and rats where a contraspecific had been detected on a card, which is consistent with previous studies of a similar duration on interspecies interference. This experiment is the first to analyse the rates at which species detections accrue over the course of a survey, and we found rat detections lagged behind possums for the first four nights. We modelled the effect of survey duration and relative rat abundance on the likelihood of further possum detections. Duration and rat abundance interacted, meaning there are trade‐offs to be considered with regard to duration: shorter durations may avoid the risk of saturation in areas of high pest density, but risk not sampling sparse or neophobic populations. Our data suggest that chew cards remain one of the most sensitive pest monitoring tools for rats and possums, compared to conventional methods such as tracking tunnels and wax tags. In areas of moderate pest densities, we suggest that a duration of five nights is optimal for detecting pests. However, in areas of high pest density the sensitivity of chew cards may render them unsuitable because of saturation and interspecies interference effects.     

FinnPRIO: a model for ranking invasive plant pests based on risk

The number of plant pests that may be transported to new areas with international trade is too great for subjecting all of them to a full scale pest risk assessment. There is therefore a need for a quick risk assessment procedure that also ranks the pests according to their risk. The FinnPRIO model can be used to assess the risk of alien plant pests for Finland. It follows the basic structure of a full scale pest risk assessment, i.e. it can be used to separately estimate the probabilities of entry, establishment (including spread), and the likely impacts. The model also includes a section for assessing preventability and controllability of a pest invasion. The model consists of multiple-choice questions with answer options yielding a different number of points. For each question the most likely answer option and the plausible minimum and maximum options are chosen. The total risk score is simulated using a PERT distribution, providing a scale of potential risk for each pest and indicating the level of uncertainty associated with the assessment. The model is accompanied by a guide for the interpretation of the questions and answer options. The model’s functionality has been tested through simulations, and it has been validated by comparing pest rankings produced using the model to those obtained in expert workshops. To date, 95 pests have been assessed with the model. The results indicate that the model is well capable of differentiating pests based on their estimated risk.     

Assessing the Risk of Invasion by Tephritid Fruit Flies: Intraspecific Divergence Matters

Widely distributed species often show strong phylogeographic structure, with lineages potentially adapted to different biotic and abiotic conditions. The success of an invasion process may thus depend on the intraspecific identity of the introduced propagules. However, pest risk analyses are usually performed without accounting for intraspecific diversity. In this study, we developed bioclimatic models using MaxEnt and boosted regression trees approaches, to predict the potential distribution in Europe of six economically important Tephritid pests (Ceratitis fasciventris (Bezzi), Bactrocera oleae (Rossi), Anastrepha obliqua (Macquart), Anastrepha fraterculus (Wiedemann), Rhagoletis pomonella (Walsh) and Bactrocera cucurbitae (Coquillet)). We considered intraspecific diversity in our risk analyses by independently modeling the distributions of conspecific lineages. The six species displayed different potential distributions in Europe. A strong signal of intraspecific climate envelope divergence was observed in most species. In some cases, conspecific lineages differed strongly in potential distributions suggesting that taxonomic resolution should be accounted for in pest risk analyses. No models (lineage- and species-based approaches) predicted high climatic suitability in the entire invaded range of B. oleae—the only species whose intraspecific identity of invading populations has been elucidated—in California. Host availability appears to play the most important role in shaping the geographic range of this specialist pest. However, climatic suitability values predicted by species-based models are correlated with population densities of B. oleae globally reported in California. Our study highlights how classical taxonomic boundaries may lead to under- or overestimation of the potential pest distributions and encourages accounting for intraspecific diversity when assessing the risk of biological invasion.     

椰子织蛾传入中国及其海南省的风险性分析

【背景】椰子织蛾原产于印度和斯里兰卡,现主要分布于南亚和东南亚,是椰子、中东海枣、蒲葵等多种棕榈科植物的重要害虫。我国目前尚无椰子织蛾发生为害的报道;但从适生性的角度看,该虫的地理分布区与我国南方棕榈植物分布区具有相似的生物气候,理论上我国热带、亚热带的广大区域是椰子织蛾的潜在地理分布区。鉴于其危害严重性,一旦入侵,其危险程度将超过已在我国发生的重要入侵害虫椰心叶甲。【方法】根据国际植物检疫措施标准（ISPM）规定的有害生物风险性分析（PRA）程序,利用相关风险性分析模型,从国内外分布状况、潜在的危害性、受害寄主的经济重要性、传播扩散的可能性及危险性管理难度5个方面,对椰子织蛾在中国及其海南省的风险性进行定性、定量分析。【结果】椰子织蛾在中国及其海南省的风险值（R）分别为2．20和2．30,在我国属于高度危险性有害生物。【结论与意义】本研究可为制定椰子织蛾的检疫管理对策提供依据。     

Predicting spread of invasive macrophytes in New Zealand lakes using indirect measures of human accessibility

1. Models predicting invasive macrophyte spread between lakes provide an important tool for focusing proactive management efforts to lakes deemed susceptible to invasion. However, challenges to forecasting macrophyte spread include wide physiological tolerances of invasive macrophytes and a lack of information on the relative importance of the various human vectors (e.g. boating traffic). In New Zealand, three invasive species that reproduce vegetatively, Ceratophyllum demersum, Lagarosiphon major, Egeria densa, and a single species that reproduces sexually, Utricularia gibba, are currently spreading across the lake landscape at a great cost to the local ecology and economy. 2. In this study, we first examined whether variables that indirectly describe weed spread via human access and use, as well as a lake’s position in the landscape, could describe the distribution of these four species using a boosted regression trees (BRT) modelling approach. Then, as these invasive species have not reached their full invasion potential, we examined how giving more influence to infected lakes at the edge of the invasion front, and including all lakes across New Zealand as background samples, simulating ‘absences beyond the invasion front’, influenced our ability to forecast the potential for new lakes to be invaded. 3. The BRT models identified that variables characterising human access and use, as well as lake position, were associated with the occurrence of the three vegetatively reproducing macrophytes. Weed occurrence was more likely when there was a highway in the vicinity, human population density was high and if the lake was large (c. 55 km²). But in the single case of U. gibba, temperature was the variable that best explained occurrence. This is consistent with the suggestion that U. gibba is predominantly dispersed by waterbirds, rather than human activity. 4. But for all four species, the BRT models based on the recorded observations alone predicted observed invasions with low prediction probabilities and did not forecast further spread. By contrast, when observations at the edge of the invasion front were upweighted, and additional background lakes implemented into the model, recorded observations were predicted and additional lakes were forecast to be at risk, suggesting that these models better captured the current and potential distribution of these macrophyte species. 5. The use of variables that characterise weed spread could provide similar insights into other systems where survey information on the nature, strength and direction of invasion vectors is lacking. Furthermore, when weighting the data, many lakes across New Zealand were forecasted to be at risk of invasion. The advantage of weighing the presence data was that insights into the potential for a species to spread were obtained. The probabilistic estimates of risk, as derived from the models, together with other information for prioritising lakes, can be used to focus surveillance and protection efforts.     

Invasion theory and biological control

Recent advances in the mathematical theory of invasion dynamics have much to offer to biological control. Here we synthesize several results concerning the spatiotemporal dynamics that occur when a biocontrol agent spreads into a population of an invading pest species. We outline conditions under which specialist and generalist predators can influence the density and rate of spatial spread of the pest, including the rather stringent conditions under which a specialist predator can successfully reverse a pest invasion. We next discuss the connections between long distance dispersal and invasive spread, emphasizing the different consequences of fast spreading pests and predators. Recent theory has considered the effects of population stage-structure on invasion dynamics, and we discuss how population demography affects the biological control of invading pests. Because low population densities generally characterize early stages of an invasion, we discuss the lessons invasion theory teaches concerning the detectability of invasions. Stochasticity and density-dependent dynamics are common features of many real invasions, influencing both the spatial character (e.g. patchiness) of pest invasions and the success of biocontrol agents. We conclude by outlining theoretical results delineating how stochastic effects and complex dynamics generated by density dependence can facilitate or impede biological pest control.     

进境台湾果蔬主要病虫风险评估与早期监测预警

[目的] 定量评估进境台湾果蔬主要病虫在大陆的入侵风险,为早期监测预警提供依据。[方法] 首先,基于外来物种传入、定殖、扩散和危害的一般过程,构建了包括4个层次26个指标的进境台湾果蔬有害生物入侵综合风险评估指标体系,规范了风险指数的计算方法,评估了14种病虫随台湾果蔬入侵的综合风险;其次,利用气候生态位模型预测了它们在我国的适生区;最后,融合进境台湾果蔬到达港口、物流中转站、集散地和主要病虫的适生区的空间分布,通过空间叠加分析划定了它们在我国传入并定殖的风险区及其空间异质性。[结果] 14种被评估病虫在我国的综合风险值均大于0.7,属高风险等级。14种病虫在我国都存在广阔的适生区,但不同物种适生区的面积和空间分布存在差异。福建、广东、海南等东部和南部沿海地区是它们适生区的高度重叠区,超过95%的台湾果蔬到达港口、物流中转和集散地的集中分布区,潜在的入侵风险极高。[结论] 进境台湾果蔬贸易能够促进或加剧外来有害生物的入侵。研究进一步证实了台湾已经并将继续成为大陆外来有害生物入侵的踏板。建议进一步加强海关检疫、开展和完善监测预警等措施预防和控制有害生物入侵,为农业生物安全提供保障。     

Ecological niche models of invasive seaweeds

Ecological niche models (ENMs) are commonly used to calculate habitat suitability from species’ occurrence and macroecological data. In invasive species biology, ENMs can be applied to anticipate whether invasive species are likely to establish in an area, to identify critical routes and arrival points, to build risk maps and to predict the extent of potential spread following an introduction. Most studies using ENMs focus on terrestrial organisms and applications in the marine realm are still relatively rare. Here, we review some common methods to build ENMs and their application in seaweed invasion biology. We summarize methods and concepts involved in the development of niche models, show examples of how they have been applied in studies on algae and discuss the application of ENMs in invasive algae research and to predict effects of climate change on seaweed distributions.     

The influence of management practice on the spatial distribution of Lepidopteran pests in <Emphasis Type="Italic">Brassica</Emphasis> crops in the Democratic People’s Republic of Korea: implications for sequential sampling plans

Plutella xylostella and Pieris rapae are the key components of a pest complex that attacks Brassica crops in the Democratic People’s Republic of Korea (DPRK). We examined the spatial distributions of these insects within crops both as individual species and when combined as a standard insect that was derived from their relative feeding rates. The influence of standard co-operative management practice and an integrated pest management (IPM) strategy on the dispersion of the standard insect was tested. Iwao’s m* − m relation was then used to describe the distribution of standard insects by management categories and of Pieris rapae using all data. Pest management practices only affected the distribution of the species when they were combined into standard insects. Enumerative sampling plans were therefore designed for standard insects based on population data derived from IPM-managed fields and for Pieris rapae from population data from all experimental fields. The presented plans have the potential to make a significant contribution to managing lepidopteran pests in the DPRK. The approach will be useful in the design of sequential sampling plans for other geographical regions where these pests co-occur and can also contribute to the development of sequential sampling plans for other pest complexes for which standard insects can be derived.     

外来有害生物风险评估方法研究进展

外来有害生物给生态环境、农业生产、人类健康带来的影响和造成的经济损失越来越受到人们的关注。与此同时,对外来有害生物风险评估方法的研究及其应用也在逐步深入。通过对多指标综合评估法、农业气候相似距法、地理信息系统、生态气候模型评价、模糊综合评判等方法的分析,概述了外来有害生物风险评估方法的含义和利弊,探讨了不同外来物种在不同环境条件下的适生性,综述了国内外评估方法应用的研究进展,对该研究领域的发展趋势进行了展望。     

Interactive effects of pests increase seed yield

Loss in seed yield and therefore decrease in plant fitness due to simultaneous attacks by multiple herbivores is not necessarily additive, as demonstrated in evolutionary studies on wild plants. However, it is not clear how this transfers to crop plants that grow in very different conditions compared to wild plants. Nevertheless, loss in crop seed yield caused by any single pest is most often studied in isolation although crop plants are attacked by many pests that can cause substantial yield losses. This is especially important for crops able to compensate and even overcompensate for the damage. We investigated the interactive impacts on crop yield of four insect pests attacking different plant parts at different times during the cropping season. In 15 oilseed rape fields in Sweden, we estimated the damage caused by seed and stem weevils, pollen beetles, and pod midges. Pest pressure varied drastically among fields with very low correlation among pests, allowing us to explore interactive impacts on yield from attacks by multiple species. The plant damage caused by each pest species individually had, as expected, either no, or a negative impact on seed yield and the strongest negative effect was caused by pollen beetles. However, seed yield increased when plant damage caused by both seed and stem weevils was high, presumably due to the joint plant compensatory reaction to insect attack leading to overcompensation. Hence, attacks by several pests can change the impact on yield of individual pest species. Economic thresholds based on single species, on which pest management decisions currently rely, may therefore result in economically suboptimal choices being made and unnecessary excessive use of insecticides.     

Biological invasion risk assessment of Tuta absoluta: mechanistic versus correlative methods

The capacity to assess invasion risk from potential crop pests before invasion of new regions globally would be invaluable, but this requires the ability to predict accurately their potential geographic range and relative abundance in novel areas. This may be unachievable using de facto standard correlative methods as shown for the South American tomato pinworm Tuta absoluta, a serious insect pest of tomato native to South America. Its global invasive potential was not identified until after rapid invasion of Europe, followed by Africa and parts of Asia where it has become a major food security problem on solanaceous crops. Early prospective assessment of its potential range is possible using physiologically based demographic modeling that would have identified knowledge gaps in T. absoluta biology at low temperatures. Physiologically based demographic models (PBDMs) realistically capture the weather-driven biology in a mechanistic way allowing evaluation of invasive risk in novel areas and climes including climate change. PBDMs explain the biological bases for the geographic distribution, are generally applicable to species of any taxa, are not limited to terrestrial ecosystems, and hence can be extended to support ecological risk modeling in aquatic ecosystems. PBDMs address a lack of unified general methods for assessing and managing invasive species that has limited invasion biology from becoming a more predictive science.