Quarantine plant pests are socially, economically and environmentally important due to their impact on food security, human health, global trade and crop production costs. The increase in global trade and tourism, frequent occurrence of natural disasters and climate changes have exacerbated the rate of entry, establishment and spread of plant pests regionally and globally. It has, therefore, become exigent to develop a list of pests of quarantine importance at the regional and national levels to prioritise and allocate the limited available resources to manage the associated risks. In the present study, the Technical Committee on the Formulation and Prioritisation of a Regional Priority Pest List for the Caribbean, in collaboration with the National Plant Protection Organisation of the Caribbean countries and the United States Department of Agriculture - Animal and Plant Health Inspection Service (USDA-APHIS), developed and prioritised a quarantine pest list using a multi-criteria decision-making approach. The technical committee successfully evolved the process in 2014 and 2018 and developed a list of the top 10 pests of quarantine importance for the Caribbean Region, employing the Delphi Technique (DT) and Analytical Hierarchy Process (AHP) through the assignment of criteria that are relevant to the region. The Mediterranean fruit fly (Ceratitis capitata), frosty pod rot (Moniliophthora roreri) and the tomato leaf miner (Tuta absoluta), listed as top quarantine pest threats, were subsequently detected in the region. This exercise guided the authorities in advance to allocate resources and to develop response plans including capacity building for surveillance and detection of priority pests. This has demonstrated the significance and appropriateness of the multi-criteria decision approach to determine priority pest lists and prepare the region for development of better management practices.

Analytical Hierarchy Process, Delphi Technique, invasiveness, quarantine pest, economic loss

The Caribbean Region, characterised by tropical and sub-tropical agriculture, is well known for its diversity. Each country is unique in culture and food habits. Due to its rich diversity, the region has been listed in the world’s 36 biodiversity hotspots with more than 1,500 unique plant species that are not present elsewhere in the world (Mittermeier et al. 2004, 2011). The region produces the popularly-known and sought-after fine flavoured cocoa, some of the hottest peppers in the world with more than one million Scoville Heat Units, high pungency ginger, richly flavoured coffee, Spice Islands ‘nutmeg’, as well as the premium quality starch from the St. Vincent arrowroot. A range of cereals (rice, corn), vegetables (tomato, hot pepper, cucurbits, cabbage, lettuce, legumes), roots and tubers (cassava, sweet potato, yam, taro), sugar-cane, coconut, spices, coffee, citrus, pineapple, plantain, banana, breadfruit and papaya are also produced for local consumption and export.

According to the Food and Agriculture Organisation of the United Nations (FAO), plants provide over 80% of the food consumed by humans and serve as the primary source of nutrition for livestock. It estimates that 40% of global crop production is lost to pests every year. Annually, plant diseases and invasive insects cost the global economy approximately US$220 billion and US$70 billion, respectively (IPPC Secretariat 2021; Ristaino et al. 2021). To date, over 10,000 fungal species associated with plants have been discovered and it is reported that fungal infections cause more harm than the diseases caused by other pathogenic micro-organisms (Hussain and Usman 2019; Nazarov et al. 2020). A viral infection can lead to 98% crop loss in tropical and sub-tropical regions (Czosnek and Laterrot 1997). Phytoplasma infections can significantly decrease both crop yield and quality. Crop losses to an extent of 40%, 60%, 93%, 30–80% and 100% were reported in eggplant, tomato, pepper, potato and cucumber, respectively specific to Phytoplasma diseases (Kumari et al. 2019). Similarly, plant-parasitic nematodes were reported to cause 12.3% crop losses with an estimated value of US$173 billion per year (Kumar et al. 2020).

Many pests of quarantine importance were also reported in the Caribbean (CABI 2012). Lethal yellowing in coconut was first observed in the Caribbean in the late 1800s and continued to be a serious problem in the Caribbean and Central America (Johnson 1912; Plavsic-Banjac et al. 1972; CARDI 2013). It was proposed that import of cattle fodder from India to the Caribbean would have carried the vector for Phytoplasma disease affecting palms (Ogle and Harries 2005; Gurr et al. 2016). Similarly, the Fusarium wilt fungus (Fusarium oxysporum f. sp. cubense race1) that devastated the Gros Michel Bananas variety in the region, might have been introduced into the Caribbean with the Silk banana variety that came from south India and, from there, spread to Central and South America (Blomme et al. 2013). The spread of the invasive hibiscus mealybug (Maconellicoccus hirsutus) and the red palm mite (Raoiella indica) had a serious impact on Caribbean agriculture. Between 1995 and 1998, an estimated total of US$18.3 million was spent on the control of hibiscus mealybug (Edwards 1999). Although total economic losses due to the pink hibiscus mealy bug have not been computed, the cost in Grenada (1995–1998) included annual losses of an estimated US$4.6 million. Amongst these was the cost of $1.1 million for the control of the mealybug and the loss of 38 hectares of blue mahoe (Talipariti elatum). The cost in St. Kitts and Nevis, including the employment of management practices, was estimated to be US$0.3 million. The potential loss to agriculture and forestry in Trinidad and Tobago was estimated to be US$125 million. The total reported loss to the Caribbean was approximately US$138 million – excluding control costs and loss of exports. It was estimated that the potential annual loss to the United States of America if the pink hibiscus mealy bug were established there, would have been US$750 million (Moffitt 1999). The introduction of the Giant African Snail (Achatina fulica) from East Africa has been a menace in the Caribbean islands of Antigua, Barbados, Dominica, Saint Lucia and Trinidad (Pollard et al. 2008). Additionally, the Mango Seed Weevil (Sternochetus mangiferae) and Black Sigatoka Leaf Spot (Mycosphaerella fijiensis) are a few more examples of economically significant pests introduced into the Caribbean (Meissner et al. 2009).

Plant pests have also been a major contributing factor to the declining productivity of key plantation crops that contributed significantly to agricultural gross domestic products earning of foreign exchange and employment generation. This in turn contributed to significant decline in these major plantation crops. Some examples of these are Witches broom in Cocoa; Citrus Tristeza Virus and Huanglongbing (HLB) in citrus production; Lethal Yellowing and Red Ring in coconuts and Black Sigatoka in bananas. The increase in agricultural trade due to a huge reliance on food imports (valued at US$5 billion), the high dependency of Small Island Developing States (SIDS) on tourism for their livelihood, the frequent occurrence of natural disasters in the region and the greater vulnerability of SIDS to climate change have intensified the chances of entry, establishment and spread of invasive pests in the region. The Caribbean Region has experienced serious economic, social and environmental challenges due to the intrusion of invasive pests (Pollard et al. 2008). When invasive alien species (IAS) are introduced into the novel habitat with enhanced survivability, they can cause widespread harm to both native and cultivated plant populations. The losses from damage and costs associated with management of established IAS could exceed the cost of measures to prevent introductions from occurring. In this regard, many National Plant Protection Organisations (NPPOs) around the world use a proactive approach through the implementation of trade restrictions as a strategy to minimise the probability of introduction of IAS. NPPOs may also use various strategies to stay informed about pest species that may threaten their respective jurisdictions. In this context, it is important to prioritise the list of pests of quarantine importance and to design strategies for preventing the entry of exotic pests into the country. The strategies include monitoring, assessing and developing capacities to identify and diagnose at all levels, developing an early warning system and risk mitigation measures and developing a national pre-border, border and post-border response plan with continuous intelligence. Furthermore, the prioritisation process guides the national and regional authorities to prioritise and allocate resources towards the implementation of appropriate quarantine and phytosanitary measures (MacLeod and Lloyd 2020).

At the same time, inconsistencies in the randomised prioritisation process may negatively impact sound judgement leading to the oversight of the differences in potential outcomes and the high-risk factors. There is, therefore, a strong need for a standard, precise and rigid valuation process that minimises biases and accommodates multiple factors when prioritising regional pests. In this context, Delphi Techniques and the Analytical Hierarchy Process (AHP) were explored in the present study.

The Delphi method, named after the ancient Greek oracle, was developed by the research organisation RAND in the 1950s to apply research and development-based decisions to predict military actions. Of late, this technique has been popularly used in economics to gain consensus amongst anonymous experts by sharing a specific research question (de Villiers et al. 2005). This technique has been demonstrated to accomplish a convergence of opinion on a specific real-world issue. This has been successfully applied in the field of medicine, social policy, tourism and sustainability where specific information is limited and contrary. However, it is less commonly applied in ecology and conservation despite its suitability in dealing with biodiversity management issues that are equally complex and involve multiple stakeholders and trade-offs (Mukherjee et al. 2015). It has the advantage of developing a full range of alternatives, exploring or exposing underlying assumptions, as well as correlating judgements on a topic spanning a wide range of disciplines. The Delphi Technique was predicated on the rationale that “two heads are better than one, or n heads were better than one”. Common surveys often try to identify “what is important”, whereas the Delphi Technique attempts to address “what is priority” (Hsu and Sandford 2007).

Similarly, the AHP has been demonstrated as a successful tool that diligently handles the multi-criteria decision-making process. Due to increasing complex nature of multi-criteria decision-making approaches, especially in the fields of agriculture and biodiversity, the process of decision-making has become more critical and challenged nowadays (Kumar and Pant 2023). This technique has allowed the selection of the best alternatives that depends on multiple criteria and sub-criteria and potentially reduces the complications by making several comparisons amongst the elements of the hierarchy. It captures both subjectivity and objectivity of associated problems and provides an ongoing measure of the consistency of the decisions obtained. Based on analysing the merits and applications of these methods in the multi-criteria decision-making approach, the current study employed Delphi Technique and AHP to prioritise the list of pests of quarantine importance for the Caribbean.

The present study was an attempt to hone the process of developing a regional priority pest list using a multi-criteria decision-making approach. The Delphi Technique was useful in the current study, based on the discussion, peer review, consultation and opinion of the experts. This was evident from the process, during which the regional technical committee initially attempted to employ the Point Score Analysis in prioritising the pest list, based on the survey with less rigour and lack of scientific evidence (data not presented).

While comparing the DT with the AHP model, the latter was seen as a structured technique for organising and analysing complex decisions. It has been used around the world in a wide variety of strategic decision-making situations, in areas such as border disputes, government, business, industry, healthcare and education. Given the complexity of some problems and the number of factors that should be simultaneously considered to derive the best possible outcome, the AHP boasts of going beyond prescribing a “correct” decision; rather, it can help decision-makers find an option that best suits their goal and their understanding of the problem. It provides a comprehensive and rational framework for structuring a decision problem, for representing and quantifying its elements, for relating those elements to overall goals and for evaluating alternative solutions (Wan et al. 2005; Szabo et al. 2021). The AHP Prioritised Pest List criteria set a strategic objective to identify high-risk quarantine pests for early detection.

The prioritisation process gave way to the first Regional Priority Pest List being completed in 2014 identifying the top 10 pests of regional priority and then once again in 2018. The Pest Prioritisation exercises were seen to be both useful and instructive for the region as the lists identified several key pests that were subsequently detected in the region: Mediterranean Fruit Fly (Ceratitis capitata) in the Dominican Republic in 2015 (Zavala-López et al. 2021), Frosty Pod Rot in Jamaica in 2016 (Ministry of Agriculture, Fisheries and Mining, Jamaica 2021) and Tuta absoluta in Haiti in May 2019 (Verheggen and Fontus 2019).

The outbreak of Mediterranean Fruit Fly was reported in the Dominican Republic in March 2015, causing an export revenue loss of US$ 40 million within 10 months of outbreak, risking 30,000 jobs (Zavala-López et al. 2021). The rapid action taken by the government, in collaboration with the FAO, the International Atomic Energy Agency (IAEA), the United States Department of Agriculture-Animal and Plant Health Inspection Service (USDA-APHIS), Organismo Internacional Regional de Sanidad Agropecuaria (OIRSA) and the Inter-American Institute for Cooperation on Agriculture (IICA), successfully eradicated the fruit fly in January 2017 through application of the sterile insect technique and integrated pest management practices. This has protected the horticulture industry of neighbouring countries in the Caribbean, Mexico and United States, circumventing significant economic losses (Zavala-López et al. 2021). It is significant to note that this pest was ranked in the top priority quarantine pest list developed in 2014 using the multi-criteria decision approach.

Similarly, various reports had been received in Jamaica that farmers were losing 40–90% of their production due to frosty pod rot disease. It was estimated to destroy anywhere between 80–100% of the entire production in the island. The first case of the frosty pod rot disease was reported to the Ministry of Agriculture in August 2016, at which point it was discovered that the parish of Clarendon was heavily infested. In a matter of approximately 4–5 months, the disease was discovered to be in the neighbouring parishes of St. Catherine, St. Andrew and St. Mary. It was suspected that the pathway of entry of the frosty pod rot disease would have been through human transmission. Based on molecular analysis, it was discovered that the strain of the frosty pod rot disease in Jamaica is similar to that in Columbia. The prioritisation of pests has assisted the region to develop strategies in advance for the management of the pests where they anticipate an entry and spread into the territory. In this case, the strategies employed in Jamaica included: (i) a delimiting survey to identify how far the disease spread, (ii) training and sensitisation of farmers and other stakeholders of the disease, (iii) creation of a buffer zone that eliminated all the conditions that the disease requires to survive and (iv) training of officers in management practices. Similarly, Huanglongbing or citrus greening disease prioritised for the Caribbean region, though identified in Jamaica earlier, was later detected in Trinidad in 2017, leading to the destruction of 200,000 citrus trees as per the Ministry of Agriculture, Trinidad and Tobago. Tomato leaf miner, ranked in the top 10 list from the 2014 and 2018 exercises, was subsequently reported in 2019 and 2021, respectively, in Haiti and Trinidad. This could pose a potential threat for dissemination to the Dominican Republic and North American countries. This has clearly demonstrated the relevance and usefulness of the priority exercise employed in the development of the regional priority pest list.

Most importantly, the use of pest prioritisation techniques has been highly beneficial to the SIDS that are characterised with poor capacity in allocating resources. The prioritisation process can guide SIDS to precisely direct its resources for the prevention and management of the quarantine pests. In addition, the employment of pest prioritisation techniques will be highly useful in determining the pathways and alerting the inspection processes at air and water borders in SIDS which are highly vulnerable to the entry of invasive pests through tourism-related activities. The prioritisation process has furthermore strengthened the local knowledge throughout the region on quarantine pests of importance. The methods used in the study have flexibility to include or exclude the criteria relevant to the changing and demanding needs of region. This model could be employed elsewhere to prioritise the national or regional pest list, based on the criterion relevant to the region. Though the AHP model permitted the ranking of the pest list, based on the relative importance of the criteria proposed, some challenges still remain due to the dependency of the model on the provision of strong scientific evidence and receipt of an unbiased list of pests. Similar to techniques, such as the Horizon Scanning method (Kendig et al. 2022) which employs arrival, establishment and impact of potential pests, the current study systematically combined and gave equal weightage to invasiveness, spread, establishment and impact to generate the pest list and then used the criteria to rank the pest list. In this context, exploring and comparison of risk-based methods, such as Horizon Scanning and the Pest Assessment and Prioritisation Process (OPEP) models with the current technique could provide further validation and reliability of the models in making multi-criteria decisions in fields like agriculture where many factors need to be considered. In addition, continuous monitoring and recording of the impact of these predictions after prioritising the pest list could provide further insights in improving these models.

Authors acknowledge the funding support of the United States Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS), the Food and Agriculture Organization of the United Nations (FAO) and the Inter-American Institute for Cooperation on Agriculture (IICA) for conducting of this exercise. Authors are listed alphabetically in this paper and not necessarily in order of their contribution to the paper.