Numerous weevil species are serious pests on agricultural crops in the Caribbean basin and the USA. These pests include native and exotic weevil (Coleoptera: Curculionoidea) species. Among them, some weevil species are easy to identify, and others need training and expertise in taxonomy in order to identify them properly. Commodity-based identification and training tools are extremely important and critical. For example, the citrus root weevil, Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) was established in the US nearly 50 yr ago, and costs millions of dollars annually in control attempts in Florida alone. Other species such as the red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Dryophthoridae); the South American palm weevil, Rhynchophorus palmarum (L.) (Coleoptera: Dryophthoridae); and the Jamaican weevil, Exophthalmus vittatus L. (Coleoptera: Curculionidae), are potential threats to fruits, vegetables, and ornamental crops. Adults of these weevils display various coloration, and patterns of red, blue, black, green, yellow, orange, and white. Some species have more than 2 color forms; male and female weevils may show major variations in their morphological characters. Regulatory agencies at the local, regional, and international levels are strengthening collaboration on offshore mitigation of these pests. Strict enforcement of regulatory guidelines and procedures is being adopted at the ports of entry into the US. Indeed, training on the identification and screening of these species, and other potential crop pests, is critically important for food security in the region. Training and capacity building to design, develop, and deploy keys, tools, and resources are major components of successful implementation of digital identification tools. The team at the Center for Biological Control is part of the digital resource consortium building tools on invasive beetles on economically important crops. To build capacity in digital insect identification, we have not only modified the contents of graduate and undergraduate insect systematics curriculum, but also have trained numerous students in these new skills.
Weevil pests of economically important crops in the Caribbean basin and the United States.
Exotic pest species introduced into the Caribbean generally constitute a regional problem, affecting numerous countries, but potentially the Caribbean region as a whole. Several exotic weevil species are already present in the Caribbean basin. The potential for introductions, deliberate or accidental, is growing through an increase in international economic and cultural links. In the Caribbean, numerous weevil species are serious pests of economically important crops or stored grains. These commodities include citrus, sugar cane, banana, palm, sweet potato, rice, coffee, stored grain, beans, cassava, pineapple, mango, sapodilla, tamarind, and others. Several pests feed on agricultural crops in the field, as well as in storage. When commodities are shipped from an island to another destination, chances of new invasion exist, and pathways are considered important points of geographical expansion of these species. Much of the management time, labor, and money invested in agricultural production is consumed by attempts to manage serious pests. In the past, several pest species (native or exotic to the Caribbean basin) have arrived in the US by either conventional agricultural trade, tourism, or trade of non-agricultural products.
For example, since 2010 the South American palm weevil, Rhynchophorus palmarum (L.) (Coleoptera: Dryophthoridae), has been attacking and killing Canary Island date palms, Phoenix canariensis Wildpret (Arecaceae), in Tijuana, Baja California, and Mexico adjacent to San Diego, California, USA (Hodel et al. 2016), and has now crossed the border into San Diego where it has killed hundreds of Canary Island date palms (Hodel, personal communication). Similarly, a number of weevil species including Rhynchophorus ferrugienus (Olivier) (Coleoptera: Dryophthoridae), Exophthalmus vittatus L. (Coleoptera: Curculionidae), Lissorhoptrus isthmicus Kuschel (Coleoptera: Brachyceridae), and Lissorhoptrus brevirostris (Suffrian) (Coleoptera: Curculionidae), are serious pests in the Caribbean basin, and can cost millions of dollars to control (O'Brien & Haseeb 2014; Fiaboe et al. 2012). Indeed, in recent times, international trade and food security rely on the enforcement of regulatory aspects of pest management. Strategic research work on the identification of potential invasive weevil species and offshore mitigation of potential pests is critical for agricultural productivity and trade (Haseeb et al. 2011a, b). The current study was undertaken to develop a web-based digital identification tool on weevil pests of economically important crops in the Caribbean pathways, and to provide hands-on training and necessary skills to graduate and undergraduate students to achieve rapid identification and detection of these weevil pests.
Material and Methods
This study was conducted in the Caribbean and other parts of the world, relying on weevil collection, loan of material, and specimen exchange(s). Lists of economically important weevils were developed from the existing literature (O'Brien & Wibmer 1982; Wibmer & O'Brien 1986), including the electronic resources available. Survey and collection were carried out in Trinidad and Tobago in summer 2009, and Aruba and Curacao in summer 2013. All specimens were identified before any imaging and digital identification work. For imaging, we have been relying exclusively on museum specimens and Auto-Montage imaging systems (Syncroscopy, http://www.directindustry.com/prod/syncroscopy/product-14153-357875.html) in the Center for Biological Control, College of Agriculture and Food Sciences, Florida A&M University, Tallahassee, Florida, USA. The weevil damage images and plant information were captured with a Nikon SLR camera and software. For identification and diagnostics, we used Lucid nutshell ( http://www.lucidcentral.com/). The software is unique to design, develop, and deploy web- and compact disc (CD)-based insect identification keys.
Weevil common characters and diagnostic characters of 2 important palm pest weevils in the Caribbean basin.
A list (Table 1) of 38 weevil species within 20 genera which included the introduced 3 species in Caribbean countries or the US, and introduced into Caribbean countries (10 species), and 25 species native to the Caribbean region is provided. However, most of these weevil species may not be from the Caribbean countries, because of intensive tourism and trade around the world. Central and South America are especially vulnerable, and serve as a hub for further spread of these exotic species to North America. Some of these species are monophagous, others are oligophagous and have narrow host plant range(s), and some are polyphagous. A web-based tool for the identification of these species was developed, and CDs were developed for users who do not have access to the internet. In this digital tool, images of dorsal and lateral habitus of these species were developed and embedded in spreadsheets. Notes on brief introduction, hosts, distribution, biology, and ecology of each species were included. The digital identification tools we have developed are based on simple distinguishing characters of weevils (25 genera and 40 species) linked with images for end-users to properly identity invasive weevil pests on economically important crops. Herein, we have provided examples of 2 exotic species: the red palm weevil, R. ferrugienus, and the South American palm weevil, R. palmarum; both are serious pests of cultivated palms, and also feed on other hosts (Figs. 1–6). Their appearance, and signs and symptoms of infestation are provided. Common and diagnostic characters of both species are provided in Table 2. Our efforts focused on providing necessary skills and hands-on training to graduate and undergraduate students to develop and deploy such digital identification tools and user-friendly identification processes (Figs. 7–10). Since spring 2009, we have trained 19 graduate and 14 undergraduate students to develop and identify insect pests, including weevil pests, based on the Lucid nutshell. Currently, these digital tools are part of the Systematic Entomology class at Florida Agricultural and Mechanical University to further train incoming students. We have organized symposia and workshops for end-users, including port of entry pest identifiers, pest managers, pest survey experts, and those involved in biodiversity and ecological studies who rely on correct identification of invasive pest species to analyze problems.
Agricultural production needs to increase considerably in the foreseeable future to meet food demands of a growing human population. Productivity of crops grown for human consumption is at risk due to the incidence of economically important crop pests. In the Caribbean, several serious weevil pest species exist that feed on economically important crops. A number of these pest species are native to the region, whereas others are exotic. Several of these species are polyphagous, and others have narrow host ranges. Because several Caribbean countries are important trade partners of the US and play a very significant role in tourism, monitoring the movements of these species in several conventional and non-conventional pathways in the Caribbean is critical to successful mitigation of these pest species. Keys to successful implementation of regionally coordinated strategies, including the development of rapid identification and detection of potential crop pests, are data exchange and joint response strategies.
Insect identifiers confront the challenge of identifying new, existing, and potentially invasive pest species. Accurate identification of insects is required before action can be determined. In the past, end-users used various approaches to identity insects, including matching with type specimens, dichotomous keys, pathway keys, matrices, and multiple entry keys (computer assisted), tabular keys (taxa vs. diagnostic characters), and punch card keys. Currently, computer-based taxonomic programs (Walter & Winterton 2007) comprising taxonomic keys, tools, and resources have become increasingly popular. Therefore, the Entomology program at Florida Agricultural and Mechanical University has been developing and training graduate and undergraduate students in this national need area.
Funding supports for this work from the USDA, NIFA Capacity Building Grants Program, and the USDA, APHIS, Center for Plant Health Sciences Technology, are greatly appreciated. We are grateful to Michael Thomas of the Florida Department of Agriculture and Consumer Sciences, Division of Plant Industry, Gainesville, Florida, USA, for weevil specimens and loans. We thank Farzan Hosein of the Ministry of Food Production, Land and Marine Affairs, St. Augustine, Trinidad and Tobago; Lizz Johnson of the CAB International, Caribbean and Central America, Curepe, Trinidad and Tobago; Ministry of Health, Environment, and Nature, Willemstad, Curacao; and Franken Facundo of the Department of Agriculture, Husbandry and Fisheries, Oranjestad, Aruba for assistance during the survey and collections of selected weevil species.