A review of pest surveillance techniques for detecting quarantine pests in Europe

Non-Destructive Pest Detection: Innovations and Challenges in Sensing Airborne Semiochemicals

Pests, especially invasive ones, pose significant threats to the global ecosystem, crop security, and agriculture economy. Sensing airborne semiochemicals as a nondestructive detection method has been recognized as a promising strategy to detect the presence of these living pests on site. However, sensing airborne semiochemicals in fields is challenging, as they are transmitted in concentrations as low as several nanograms per cubic meter in chemically diverse environments. This low vapor pressure together with similarity in functional groups of pheromones among different species have curtailed the practical deployment of corresponding sensors for real world applications. This review describes the advances in semiochemical detection methods and technologies including traditional analytical instruments, trained animals, and electroantennography with a focus on electronic noses (e-noses). Several key types of volatile organic compound (VOC) sensors used in e-noses are summarized, including their transduction methods, sensing materials, and sensing performance for semiochemical and simulants detection. Notably, it was found that many commercial VOC sensors failed to respond to airborne semiochemicals effectively, leading to a reduced efficiency of e-noses. Future work may focus on developing stable and robust sensing materials with higher sensitivity and selectivity to pheromones and understanding the feasibility of the deployment of the sensors under field conditions.

Addition of Selected Plant-Derived Semiochemicals to Yellow Sticky Traps Does Not Improve Citrus Psyllid Captures

Fast and effective monitoring and surveillance techniques are crucial for the swift implementation of control methods to prevent the spread of Huanglongbing, a devastating citrus disease, and its invasive psyllid vector, Asian citrus psyllid, Diaphorina citri, into South Africa, as well as to control the native vector, African citrus triozid, Trioza erytreae. Monitoring for citrus psyllid pests can be improved by using semiochemical odorants to augment already visually attractive yellow sticky traps. However, environmental variables such as temperature and humidity could influence odorant release rates. Five field cages were used to test the ability of a selection of odorants to improve yellow sticky trap efficacy in capturing citrus psyllids. Environmental effects on odorant loss from the dispensers were also investigated. The odorants that most improved yellow sticky trap captures in field cages were then tested under open field conditions alongside lower concentrations of those same lures. Gas chromatography-mass spectrometry was used to calculate odorant release rates as well as to determine if any contamination occurred under field conditions. None of the odorants under field cage or field conditions significantly improved psyllid capture on yellow sticky traps. Temperature influenced odorant loss, and release rate from polyethylene bulbs decreased over time. Based on these results, the use of unbaited yellow sticky traps seems to be the most effective method for monitoring of Huanglongbing vectors.

PCR-Based Detection for the Quarantine Fungus Colletotrichum kahawae, a Biosecurity Threat to the Coffee (Coffea arabica) Industry Worldwide

Coffee berry disease is caused by Colletotrichum kahawae, a quarantine fungus still absent from most coffee-producing countries. Given the potential adverse effects on coffee berry production, it is a severe worldwide threat to farmers and industry. Current biosecurity management focuses on exclusion by applying quarantine measures, including the certification of coffee plants and their products. However, methods for detecting C. kahawae by National Plant Protection Organization (NPPO) laboratories still need approval. This research aims to functionally demonstrate, standardize, and validate a method for detecting and discriminating C. kahawae from other Colletotrichum species that may be present in coffee plant samples. The method proposes to use an end-point PCR marker for the mating type gene (MAT1-2-1) and a confirmatory test with a real-time quantitative PCR (qPCR) marker developed on the glutamine synthetase gene. The C. kahawae amplicons for the Cen-CkM10 qPCR marker exhibited specific melting temperature values and high-resolution melt profiles that could be readily differentiated from other tested species, including their relatives. Given the fungus's quarantine status, specificity was tested using artificial mixtures of DNA of C. kahawae with other Colletotrichum species and coffee plant DNA. The described method will enable NPPOs in coffee-producing and exporting countries, especially Colombia, to prevent this pathogen's entry, establishment, and spread.[Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Predicting the Potential Global Distribution of the Plum Fruit Moth Grapholita funebrana Treitscheke Using Ensemble Models

The plum fruit moth, Grapholita funebrana Treitschke, is one of the most significant borer pests, often causing huge economic losses in fruit production. However, the potential distribution range of this economically important pest is still poorly understood. For this study, we simulated an ensemble species distribution model to predict the spatiotemporal distribution pattern of G. funebrana at a global scale. The results show that the suitable habitats for this moth, under current environmental conditions, are mainly distributed in Europe; East Asia, including China and Japan; Central Asia; and some parts of America. In future projections, the suitable habitats are predicted to generally expand northward, while the suitable area will remain unchanged overall. However, the area of highly suitable habitat will decrease to only 17.49% of that found under current conditions. None of the nine factors used were revealed to be predominant predictors in terms of contributing to the model, suggesting that the integrated effects of these variables shape G. funebrana's distribution. In this study, the distribution range that has been predicted, especially for the regions with a highly suitable habitat, poses a high risk of G. funebrana outbreaks, highlighting the urgency of pest management. Moreover, in the United States of America (USA) and Japan (for which G. funebrana distributions were not previously recorded), especially in areas highly suitable for this moth, monitoring and quarantine measures should be strengthened to prevent the colonization and further dispersal of this pest, as seen with its close relative G. molesta, which has become a cosmopolitan pest species, migrating from its native region (East Asia) to other continents, including the Americas.

Forest Insect Biosecurity: Processes, Patterns, Predictions, Pitfalls

The economic and environmental threats posed by non-native forest insects are ever increasing with the continuing globalization of trade and travel; thus, the need for mitigation through effective biosecurity is greater than ever. However, despite decades of research and implementation of preborder, border, and postborder preventative measures, insect invasions continue to occur, with no evidence of saturation, and are even predicted to accelerate. In this article, we review biosecurity measures used to mitigate the arrival, establishment, spread, and impacts of non-native forest insects and possible impediments to the successful implementation of these measures. Biosecurity successes are likely under-recognized because they are difficult to detect and quantify, whereas failures are more evident in the continued establishment of additional non-native species. There are limitations in existing biosecurity systems at global and country scales (for example, inspecting all imports is impossible, no phytosanitary measures are perfect, knownunknowns cannot be regulated against, and noncompliance is an ongoing problem). Biosecurity should be a shared responsibility across countries, governments, stakeholders, and individuals.

The Rapid Identification of Anoplophora chinensis (Coleoptera: Cerambycidae) From Adult, Larval, and Frass Samples Using TaqMan Probe Assay

A molecular diagnostic method using TaqMan probe qPCR is presented for the identification of Anoplophora chinensis (Förster) (Coleoptera: Cerambycidae) from whole body insects (adults and larvae) and frass samples stored under different conditions. The results showed a perfect amplification of DNA from all samples; the repeatability and reproducibility of the protocol were very good, with standard deviations of inter-run and intra-run variability less than or equal to 0.5. The assay allowed to discern all A. chinensis samples from those of the other non-target wood-borer species, with 100% correspondence to the homologous sequences. No amplification or cross reactions were observed with A. glabripennis (Motschulsky) (Coleoptera: Cerambycidae), which is the most related species among those tested. The protocol was validated by an internal blind panel test which showed a good correspondence between the results obtained by different operators in the same lab. The analytical sensitivity for the lab frass with the Probe qPCR, namely the lowest amount of A. chinensis DNA that can be detected (LoD), was 0.64 pg/µl with a Cq of 34.87. The use of indirect evidence for the identification of a pest is an important feature of the method, which could be crucial to detect the presence of wood-boring insects. This diagnostic tool can help prevent the introduction of A. chinensis into new environments or delimit existing outbreak areas thanks to indirect frass diagnosis.

Improved Light Traps for Early Detection of Insect Pests of Phytosanitary Concern in Shipping Containers

The number of introductions of alien insect has been increasing in the last decades, primarily transported in shipping containers. The attraction of light of different wavelengths (white, infrared, ultraviolet, and red) applied on sticky traps was tested for the development of new traps for hitchhiker insects. The addition of entomological glue and insecticide on the trap was also tested. Tests were conducted on Cadra cautella Walker (Lepidoptera: Pyralidae), Drosophila melanogaster Meigen (Diptera: Drosophilidae), Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and released inside a shipping container. In the first test, one light color at a time was tested setting eight traps in the container, one for each possible combination of the variables: light on or off, glue added or not, and insecticide sprayed or not. In the second, five traps were used, all of them coated with the entomological glue: one for each light color and one with light off as control. In all the single color tests (except for infrared), light-on traps captured more, except for T. castaneum that was not attracted to white. In the multi-color test, C. cautella showed no preference among white, ultraviolet, or red; Drosophila melanogaster preferred ultraviolet and white over red; and beetles had a much greater attraction to red. Lastly, the stronger entomological glue improved catches of beetles, whereas insecticides did not. In conclusion, results suggest a possible application of sticky light traps against hitchhiker insects and further studies should verify if the simultaneous use of different light colors can improve the trap performance and does not act as a repellent.

Development of Three Molecular Diagnostic Tools for the Identification of the False Codling Moth (Lepidoptera: Tortricidae)

Three molecular protocols using qPCR TaqMan probe, SYBR Green, and loop-mediated isothermal amplification (LAMP) methods were set up for the identification of larvae and adults of an African invasive moth, Thaumatotibia leucotreta (Meyrick, 1913) (Lepidoptera: Tortricidae). The DNA extracts from larval and adult samples of T. leucotreta were perfectly amplified with an average Ct value of 19.47 ± 2.63. All assays were demonstrated to be inclusive for T. leucotreta and exclusive for the nontarget species tested; the absence of false positives for nontarget species showed a 100% of diagnostic specificity and diagnostic sensitivity for all assays. With the SYBR Green protocol, the Cq values were only considered for values less than 22 (cutoff value) to prevent false-positive results caused by the late amplification of nonspecific amplicons. The limit of detection (LoD) for the qPCR probe protocol was equal to 0.02 pg/µl while a value equal to 0.128 pg/µl for the qPCR SYBR Green assay and LAMP method were established, respectively. The intrarun variabilities of reproducibility and repeatability in all the assays evaluated as CV%, ranged between 0.21 and 6.14, and between 0.33 and 9.52, respectively; the LAMP values were slightly higher than other assays, indicating a very low interrun variability. In order for an operator to choose the most desirable method, several parameters were considered and discussed. For future development of these assays, it is possible to hypothesize the setup of a diagnostic kit including all the three methods combined, to empower the test reliability and robustness.

A molecular method for biomonitoring of an exotic plant-pest: Leafmining for environmental DNA

Understanding how invasive species respond to novel environments is limited by a lack of sensitivity and throughput in conventional biomonitoring methods. Arthropods in particular are often difficult to monitor due to their small size, rapid lifecycles, and/or visual similarities with co-occurring species. This is true for the agromyzid leafminer fly, Liriomyza sativae, a global pest of vegetable and nursery industries that has recently established in Australia. A robust method based on environmental DNA (eDNA) was developed exploiting traces of DNA left inside "empty" leaf mines, which are straightforward to collect and persist longer in the environment than the fly. This extends the window of possible diagnosis to at least 28 days after a leaf mine becomes empty. The test allowed for visually indistinguishable leafmining damage caused by L. sativae to be genetically differentiated from that of other flies. Field application resulted in the identification of new local plant hosts for L. sativae, including widely distributed weeds and common garden crops, which has important implications for the pest's ability to spread. Moreover, the test confirmed the presence of a previously unknown population of L. sativae on an island in the Torres Strait. The developed eDNA method is likely to become an important tool for L. sativae and other leafmining species of biosecurity significance, which, historically, have been difficult to detect, diagnose and monitor. More generally, eDNA is emerging as a highly sensitive and labour-efficient surveillance tool for difficult to survey species to improve outcomes for agricultural industries, global health, and the environment.

TaqMan probe assays on different biological samples for the identification of three ambrosia beetle species, Xylosandrus compactus (Eichoff), X. crassiusculus (Motschulsky) and X. germanus (Blandford) (Coleoptera Curculionidae Scolytinae)

Molecular assays based on qPCR TaqMan Probes were developed to identify three species of the genus Xylosandrus, X. compactus, X. crassiusculus and X. germanus (Coleoptera Curculionidae Scolytinae). These ambrosia beetles are xylophagous species alien to Europe, causing damages to many ornamental and fruiting trees as well as shrubs. DNA extraction was carried out from adults, larvae and biological samples derived from insect damages on infested plants. For X. compactus, segments of galleries in thin infested twigs were cut and processed; in the case of X. crassiusculus, raw frass extruded from exit holes was used, while DNA of X. germanus was extracted from small wood chips removed around insect exit holes. The assays were inclusive for the target species and exclusive for all the non-target species tested. The LoD was 3.2 pg/µL for the frass of X. crassiusculus and 0.016 ng/µL for the woody matrices of the other two species. Both repeatability and reproducibility were estimated on adults and woody samples, showing very low values ranging between 0.00 and 4.11. Thus, the proposed diagnostic assays resulted to be very efficient also on the woody matrices used for DNA extraction, demonstrating the applicability of the protocol in the absence of dead specimens or living stages.

Development of a loop-mediated isothermal amplification (LAMP) assay for the identification of the invasive wood borer Aromia bungii (Coleoptera: Cerambycidae) from frass

The red-necked longhorn beetle Aromia bungii (Faldermann, 1835) (Coleoptera: Cerambycidae) is native to east Asia, where it is a major pest of cultivated and ornamental species of the genus Prunus. Morphological or molecular discrimination of adults or larval specimens is required to identify this invasive wood borer. However, recovering larval stages of the pest from trunks and branches causes extensive damage to plants and is timewasting. An alternative approach consists in applying non-invasive molecular diagnostic tools to biological traces (i.e., fecal pellets, frass). In this way, infestations in host plants can be detected without destructive methods. This paper presents a protocol based on both real-time and visual loop-mediated isothermal amplification (LAMP), using DNA of A. bungii extracted from fecal particles in larval frass. Laboratory validations demonstrated the robustness of the protocols adopted and their reliability was confirmed performing an inter-lab blind panel. The LAMP assay and the qPCR SYBR Green method using the F3/B3 LAMP external primers were equally sensitive, and both were more sensitive than the conventional PCR (sensitivity > 10³ to the same starting matrix). The visual LAMP protocol, due to the relatively easy performance of the method, could be a useful tool to apply in rapid monitoring of A. bungii and in the management of its outbreaks.

Molecular Identification of Anoplophora glabripennis (Coleoptera: Cerambycidae) From Frass by Loop-Mediated Isothermal Amplification

Anoplophora glabripennis (Motschulsky, 1853), native to eastern Asia, is a destructive woodborer of many ornamental species, leading to the decline and the death of the attacked trees. In outbreak areas as Europe or North America, this pest is usually identified using morphological or molecular analyses of adult or larval specimens. However, the procedures for collecting A. glabripennis specimens from infested plants are too expensive and time consuming for routine screening. A noninvasive diagnostic tool based on frass discrimination is therefore crucial for the rapid identification of A. glabripennis at different development stages in the host. This article describes a rapid diagnostic protocol based on loop-mediated isothermal amplification (LAMP). DNA extracted from A. glabripennis frass was amplified with both visual and real-time LAMP and compared with those of nontarget species. The results show that the method is reliable and accurate and therefore could be a promising diagnostic tool in phytosanitary surveys.

Peering into the Cuba phytosanitary black box: An institutional and policy analysis

To mitigate the movement of non-native organisms with trade, phytosanitary systems have been implemented within and between countries. In some countries such as Cuba, little is known about the within-state plant health system. To facilitate the development of future trade partnership between Cuba and the United States, agencies need to understand the organizational structure and diagnostic capacity of the Cuban Plant Protection System, identify potential synergies between the United States and Cuban systems, and identify steps towards cooperation. This paper fills this critical void by presenting a descriptive analysis of the plant health system in Cuba. Information was integrated from available literature, informal interviews with Cuban experts, and workshops focused on Cuban policies, risk, and potential collaboration attended by Cuban and American experts. We identify the next practical steps in improving cooperation, including building trust and capacity. Mutual understanding of phytosanitary systems will be crucial for the regional economic and environmental stability of a post-embargo United States-Cuban relationship.

A New System for Detecting Initial Colonization by Invasive Pests and Their Locations

Quarantine pests in plants can be a serious agricultural problem; many eradication programs using area-wide control measures have been implemented worldwide to combat this threat. Surveillance measures using sex pheromone (in general, male-attractant) traps are also widely implemented for rapid control and eradication of invasive pests. If initial pest colonization can be determined based on temporal count data of trapped insects (i.e., males), and countermeasures are applied only during colonization, costs incurred by these countermeasures would be dramatically reduced, especially in areas with frequent invasions. In this study, we developed a system to detect initial pest colonization, and to narrow down colonized regions using estimated temporal count data of the sweet potato weevil, Cylas formicarius Fabricius (Coleoptera: Curculionidae), in Tsuken Island, Okinawa, Japan. We verified the system by comparing our estimates to actual colonization data obtained via regular host plant surveys. Results indicated that our system was able to successfully detect pest colonization and estimate colonized regions. In this study, we discuss the conditions (i.e., pest biology, environment, etc.) that are optimal for application of our system.

Using DNA barcoding to improve invasive pest identification at U.S. ports-of-entry

Interception of potential invasive species at ports-of-entry is essential for effective biosecurity and biosurveillance programs. However, taxonomic assessment of the immature stages of most arthropods is challenging; characters for identification are often dependent on adult morphology and reproductive structures. This study aims to strengthen the identification of such specimens through DNA barcoding, with a focus on microlepidoptera. A sample of 241 primarily immature microlepidoptera specimens intercepted at U.S. ports-of-entry from 2007 to 2011 were selected for analysis. From this sample, 201 COI-5P sequences were generated and analyzed for concordance between morphology-based and DNA-based identifications. The retrospective analysis of the data over 10 years (2009 to 2019) using the Barcode of Life Data (BOLD) system demonstrates the importance of establishing and growing DNA barcode reference libraries for use in specimen identification. Additionally, analysis of specimen identification using public data (43.3% specimens identified) vs. non-public data (78.6% specimens identified) highlights the need to encourage researchers to make data publicly accessible. DNA barcoding surpassed morphological identification with 42.3% (public) and 66.7% (non-public) of the sampled specimens achieving a species-level identification, compared to 38.3% species-level identification by morphology. Whilst DNA barcoding was not able to identify all specimens in our dataset, its incorporation into border security programs as an adjunct to morphological identification can provide secondary lines of evidence and lower taxonomic resolution in many cases. Furthermore, with increased globalization, database records need to be clearly annotated for suspected specimen origin versus interception location.

Eradication of Invading Insect Populations: From Concepts to Applications

Eradication is the deliberate elimination of a species from an area. Given that international quarantine measures can never be 100% effective, surveillance for newly arrived populations of nonnative species coupled with their eradication represents an important strategy for excluding potentially damaging insect species. Historically, eradication efforts have not always been successful and have sometimes been met with public opposition. But new developments in our understanding of the dynamics of low-density populations, the availability of highly effective treatment tactics, and bioeconomic analyses of eradication strategies offer new opportunities for developing more effective surveillance and eradication programs. A key component that connects these new developments is the harnessing of Allee effects, which naturally promote localized species extinction. Here we review these developments and suggest how research might enhance eradication strategies.

Designing cost-efficient surveillance for early detection and control of multiple biological invaders

Wood borers and bark beetles are among the most serious forest pests worldwide. Many such species have become successful invaders, often causing substantial, costly damages to forests. Here we design and evaluate the cost-efficiency of a trap-based surveillance program for early detection of wood borers and bark beetles at risk of establishing in New Zealand. Although costly, a surveillance program could lead to earlier detection of newly established forest pests, thereby increasing the likelihood of successful eradication and reducing control costs and damages from future invasions. We develop a mechanistic bioeconomic model that relates surveillance intensity (i.e., trap density) and invasion size to probabilities of detection and control. It captures the dynamics of invasive species establishment, spread, and damages to urban and plantation forests. We employ the model to design surveillance programs that provide the greatest net present benefits. Our findings suggest that implementing a surveillance trapping program for invasive wood borers and bark beetles would provide positive net benefits under all scenarios considered. The economically optimal trapping strategy calls for a very high investment in surveillance: about 10 000 traps in each year of the 30-year surveillance program, at a present value cost of US$54 million. This strategy provides a 39% reduction in costs compared with no surveillance, corresponding to an expected net present benefit of approximately US$300 million. Although surveillance may provide the greatest net benefits when implemented at relatively high levels, our findings also show that even low levels of surveillance are worthwhile: the economic benefits from surveillance more than offset the rising costs associated with increasing trapping density. Our results also show that the cost-efficiency of surveillance varies across target regions because of differences in pest introduction and damage accumulation rates across locales, with greater surveillance warranted in areas closer to at-risk, high-value resources and in areas that receive more imported goods that serve as an invasion pathway.