Benefits and Challenges of Maintaining National Plant Pest Lists: an Analysis of Agricultural Pests in Bhutan

Developing and maintaining national plant pest lists helps fulfil international obligations for trading countries, and also provides a foundation for national biosecurity systems. However, if done, lists and analyses are rarely made publically available. We compiled a national plant pest list for Bhutan, a relatively small but agriculturally diverse country for which plant protection is a recent discipline. We treated this pest list as a case study to test the benefits and challenges of maintaining such lists. Six hundred and forty-five pest species were recorded across 64 different crops. Of those, only 17.0% were listed for Bhutan in the widely used CABI Crop Protection Compendium. Most species (86.4%) were first recorded during the initial discovery phase (1985-88) of a long-running European Community funded aid programme. Regular taxonomic changes means keeping pest lists up to date requires both effort and expertise (27.0% of the 407 species identified by 1988 have since undergone name changes). Confidence in taxonomic identifications reduced drastically as access to international expertise decreased, from about 69.1% of species being identified with high confidence prior to 1988 to 8.1% afterwards. Many recent records lacked reference material, and voucher specimens for older material are mostly located internationally, making any revision challenging. Of the best represented taxa, greatest taxonomic uncertainty was for nematodes and viruses. Similar patterns were evident for the 112 damaging pest species, defined as those that at least occasionally and locally cause significant losses or require management actions within Bhutan. Of the damaging pests identified to species, all but one was also recorded in India, Bhutan's most important trading partner, and only 16 were restricted to Asia. New damaging pests continue to be recorded, but only five species may represent new incursions since 1988. National pest lists are critical, but to be of greatest value they need to capture taxonomic uncertainty, and focus on pests of greatest significance. For most countries, the development, maintenance and use of a national plant pest list will require ongoing regional and global cooperation to overcome taxonomic impediments, and to maximise the benefits of such lists in terms of facilitating trade and guiding domestic biosecurity activities.