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Fourteenth Australian Weeds Conference Working with weeds in the Land of the Thunderdragon: an opportunity to prevent weed invasions John Weiss1, T. Thinley2, Karma Nidup2, Mahesh Ghimiray3, Sangay Wandi3 and Tshering Dochen2 1 Department of Primary Industries – Frankston, PO Box 48, Frankston, Victoria 3199, Australia 2 National Plant Protection Centre, Ministry of Agriculture, Simtokha, Bhutan 3 Renewable National Resources Research Centre, Ministry of Agriculture, Bajo, Bhutan Summary Bhutan is in one of the most enviable posi- to be overlooked or have low priority both by the gen- tions in the world in terms of weeds. The kingdom in eral public and government. Expertise in weed science the Himalayas has only been open to the rest of the is lacking in the country. Most weed control programs world since the mid 1960s. As the country has never have reacted and focused on agricultural weeds and been conquered there has been no colonisation or ac- weeds which are relatively widespread. Environmental climatisation societies. A total of 72% of the country weeds are almost totally overlooked. is still under its original remnant vegetation. A survey Bhutan has the potential to be proactive rather in the late 1980s and early 1990s (Parker 1991, 1992) than reactive to weeds at a minimal cost. Awareness identifi ed over 250 species of introduced plants, less of weeds in general needs to be increased as well as than 5% of Bhutan’s fl ora. precautionary measures to prevent future weeds. However, there is a cloud on the horizon. There is Keywords Risk assessment, plant imports, weed an increase in plant material being brought into Bhu- invasions, Bhutan. tan, usually deliberately. For example, English Broom, Cytisus scoparius L., was recently planted in central INTRODUCTION Bhutan, reportedly by a European aid agency. For its size, just over 40,000 square km, Bhutan has A review of recent plant imports for fodder, an extremely rich fl ora, now known to be 5603 spe- forestry or pasture revealed a disturbing and familiar cies. This includes 82 endemics, found nowhere else pattern. Of the 127 species checked, 72 (57%) were in the world (Grierson and Long 1983). The reason assessed to be potentially either very serious or major for this richness is partly to do with the position of weeds for Bhutan in the future. Bhutan within the east Himalayas, between India and Bhutan has a rich biodiversity and sustainable agri- Tibet (Figure 1), but also because of the fi ne state of culture that is threatened by weed invasion. Weeds tend preservation of its vegetation (with 72.5% of its area Figure 1. Relative position of Bhutan in Asia. 488 Fourteenth Australian Weeds Conference still forested). The range of habitats is also large – from Table 1. List of plant species imported into Bhutan subtropical lowlands at 200 m above sea level in the from 1997–2000 for fodder, feed and forestry (spe- south, to extreme alpine conditions in the north, with cies names have been left as recorded in the reports several mountain peaks of over 7000 m. and may contain spelling errors or be synonyms of Bhutan has never been colonised or had acclima- other species). tisation societies planting exotic species and has only Acacia arabica Acacia villosa relatively recently, since the mid 1960s, been open to Aeschynomene americana Aeschynomene histrix the outside world. In conjunction with the Royal Bo- Aeschynomene villosa Andropogon gayanus tanic Garden, Edinburgh, a census of Bhutan’s Flora Arachis pintoi Brachiaria brizantha has been ongoing since 1980. Over 5000 species of Brachiaria decumbens Brachiaria humidicola fl owering plants have been identifi ed. A review of the Cedrela toona Cenchrus ciliaris weed fl ora occurred in the late 1980s and 1990s. Al- Centrosema acutifolium Centrosema arenarium though not a comprehensive survey (with mainly an Centrosema pascuorum Centrosema pubescens agricultural focus and predominately limited to central Chamaecrista rotundifolia Chamaecytisus proliferus and northern areas of Bhutan – corresponding to the Chloris gayana Clitoria ternatea more temperate and alpine regions), relatively few, Desmanthus virgatus Desmodium intortum 251 naturalised weed species, were found, less than Desmodium nicaraguense Desmodium rensonii 5% of the fl ora (Parker 1991, 1992). In comparison, Desmodium uncinatum Ficus roxburghii Australia in over 200 years has over 2500 naturalised Gmelina arborea Lablab purpureus species, over 25% of its fl ora (Martin 2004). Leucaena leucocephala Lotus pedunculatus Lupinus angustifolius Macroptilium atropurpureum Macroptilium gracile Macrotyloma axillare MATERIALS AND METHODS Macrotyloma daltonii Medicago sativa A review of annual reports from the Ministry of Melilotus alba Melilotus offi cinalis Agriculture’s research centres showed that there had Neonotonia wightii Panicum coloratum been 60 species of plants imported into Bhutan for Panicum maximum Paspalum atratum fodder, feed and forestry from 1997–2000. There Paspalum guenoarum Pueraria phaseoloides were no easily accessible records prior to 1997 except Robina psedoacacia Setaria sphacelata for grasses. Some 67 grasses were introduced into Stylosanthes capitata Stylosanthes guianensis Bhutan for fodder since 1974 (Noltie 2000). A total Stylosanthes hamata Stylosanthes scabra of 127 species of trees, shrubs and grasses (Tables 1 Stylosanthes viscosa Tamarindus indica and 2) were assessed for their potential to be serious Teramnus uncinatus Teramnus uncinatus weeds in Bhutan. ‘The World’s Worst Weeds’ (Holm Tithonia diversifolia Trifolium incarnatum et al. 1997) and ‘A Global Compendium of Weeds’ Trifolium rueppellianum Urochloa mosambicensis (Randall 2002) were used to identify a species’ prior Vigna parkeri Zornia latifolia weed history. The defi nition of very serious, serious or major weed corresponded with categories outlined by and weedy Phalaris aquatica and Phleum pratensis Holm et al. 1997, or by the number of countries where for Phleum pratense. it was recorded as a weed in ‘A Global Compendium A review of the weed potential of four boxes of of Weeds’. seeds sent from Japan to the Royal Botanic Gardens, Serbithang, identifi ed a number of plants with major RESULTS or serious weed potential. The seed packets and their Of the 60 species introduced for fodder, feed or for- scientifi c names were cross-referenced against the two estry since 1997, 32 were identifi ed as major weeds major databases of weeds worldwide. The following and four as very serious weeds, a total of 60% of the plants were found to be major, serious or very serious plants imported. weeds elsewhere in the world and could pose a threat to Grasses that were imported for fodder also had Bhutan’s social, environmental or agricultural values. similar potential. Of the 67 species introduced since Cosmos bipinatus Serious 1974, 18 of these are major and another 18 are very Euphorbia margia Serious serious weeds, a total of 54% of the introductions. Only Limonium sinuatum Major one species, Paspalum guenoarum, had no weed his- Mimosa pudica Very serious tory. Of the 67 species, 18 (26%) have already become Portulaca grandifl ora Major naturalised in Bhutan. Two of the minor weed species Rudbeckia hirta Major may have been misnamed and could be more weedy; Cirsium japonicum Major Phalaris tuberosa is a synonym for the more invasive Nigella damascena Major 489 Fourteenth Australian Weeds Conference Table 2. List of grass species imported into Bhutan to taking ‘sanitary and phytosanitary measures’ to since 1974 for fodder (species names have been left protect human, animal or plant life or health, ‘taking as recorded in Noltie 2000). into account risk assessment techniques developed Agropyron trachcaulum Agropyron desertorum by the relevant international organisations’ – that is, Agropyron elongatum Agropyron inerme the International Plant Protection Convention (IPPC) Agropyron intermedium Agropyron smithii (Nairn et al. 1996). Agrostis alba Agrostis tenuis The Plant Quarantine Act of Bhutan 1993 ena- Alopecurus arundinaceus Alopecurus pratensis bles the Royal Government by regulation to declare Andropogon gayanus Andropogon gerardi any plant a quarantine plant pest. Section (1c) of the Arrhenatherum elatius Avena sativa Act states that the Royal Government can ‘prohibit Bothriochloa caucasica Bothriochloa insculpta absolutely the import into Bhutan from any country, Bothriochloa ischaemum Bothriochloa pertusa or countries, outside Bhutan of plants, goods, plant Brachiaria brizantha Brachiaria decumbens products and soil which are likely to be a means of Brachiaria humidicola Brachiaria ruziziensis introducing or spreading plant pests into the country Bromus catharticus Bromus erectus for the purposes of international plant quarantine.’ Bromus inermis Cenchrus ciliaris Since early 2002, under Regulation 2, Schedule 4b Chloris gayana Cynosurus cristatus of The Plant Quarantine Act of Bhutan 1993, the im- Dactylis glomerata Digitaria milanjiana port and raising of Eucalyptus species has been banned Digitaria natalensis Digitaria setivalva by royal command of His Majesty the King upon his Digitaria smutsii Echinochloa utilis hearing of the invasiveness and spread of the plants. Elymus dahuricus Elymus junceus In addition many Eucalyptus trees already planted in Elymus sibiricus Festuca arundinacea Bhutan were cut down. While The Plant Quarantine Festuca ovina Festuca pratensis Festuca rubra Holcus lanatus Act of Bhutan 1993 does enable the prohibition of Lolium multifl orum Lolium multifl orum × plant species

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