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Planning for Effective Weed Management: Lessons from Sri Lanka

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Planning for Effective Weed Management: Lessons from Sri Lanka 23rd Asian-Pacific Weed Science Society Conference The Sebel Cairns, 26-29 September 2011 PLANNING FOR EFFECTIVE WEED MANAGEMENT: LESSONS FROM SRI LANKA Rohan Rajapakse1, Nimal Chandrasena2, Buddhi Marambe3 and Lakshman Amarasinghe4 1University Grants Commission, 20, Ward Place, Colombo 7, Sri Lanka, 1ALS Water Sciences Group, 24A, Lemko Place, Penrith, NSW 2750, Australia, 3 Faculty of Agriculture, University of Peradeniya, Sri Lanka, 4 Department of Agriculture, Peradeniya, Sri Lanka ABSTRACT In tropical Sri Lanka, Water Hyacinth [Eichhornia crassipes (Mart.) Solms.] and Salvinia (Salvinia molesta D. S. Mitchell) continue to dominate eutrophic waterways in both rural and urban environments. In addition, several other highly invasive species have also recently become problems in waterways, and these include: Alligator Weed [Alternanthera philoxeroides (Mart.) Griseb], Water Spinach Ipomoea aquatica Forssk. and Hydrilla [Hydrilla verticillata (L. f.) Royle]. Infestations of Primrose Willows - Ludwigia peruviana (L.) Hara and L. octovalvis are increasing in abundance in reclaimed marshlands and drainage canals, while several others (e.g. L. decurrens and L. hyssopifolia) continue to be major weed problems in rice agriculture. Relatively recent introductions of major global weeds (i.e. Giant Mimosa – Mimosa pigra L.; Parthenium - Parthenium hysterophorus L.; Austroeupatorium inulifolium (Kunth) R.M. King & H.Rob.) highlight Sri Lanka‘s problems. Their pattern of spread, via major roads, is attributable to accelerated development of infrastructure and use of contaminated machinery. Two recent escapees from aquarium industry: Mayaca fluviatilis Aubl. and Ludwigia sedioides L. are now spreading, at least in one district. Sri Lanka has a poor record of managing weeds, largely due to inadequate mechanisms to deal with them early, or prevent their entry through border protection. Recent stakeholder consultations identified insufficient funding for on-ground works and for research; and the absence of a central coordination mechanism, as major constraints. Control options are also limited (i.e. limited array of herbicides, or bio-control agents) and experience is also lacking in implementing large-scale integrated weed management programs. To effectively tackle invasive species in Sri Lanka, a National Weed Strategy (NWS) has been developed. This national framework aims to provide increased weed science education at tertiary level and increased training for government officials and farmers. It also aims provide a mechanism for efficient information sharing and effective multiple-stakeholder cooperation and participation in managing weeds across landscapes. Keywords: Aquatic weeds, Sri Lanka, National Weed Strategy 116 23rd Asian-Pacific Weed Science Society Conference The Sebel Cairns, 26-29 September 2011 INTRODUCTION The agriculture sector in Sri Lanka provides livelihood for around 35% of the country‘s work force and contributes around 19% of GDP. This sector comprises: food crops (e.g. rice, pulse crops and vegetables), plantation crops (Tea, Rubber and Coconut) and export crops (Pepper, Cloves and Nutmeg etc.) and. Weeds are a major constraint to achieving high productivity and self-sufficiency in aagriculture, and in some cases, weeds reduce crop yields (quantity) by as much as 50%. Weeds also reduce the quality of crop produce, thereby reducing the overall productivity of land and farmers‘ income from agriculture. Weeds reduce the quality the island‘s uniquely native biodiversity and have many negative impacts on the health of waterways and aquatic resources (Amarasinghe and Marambe, 1997; Bambaradeniya et al., 2001; Marambe, et al., 2001; MFE, 1999). Until the recent centuries and colonial interventions, the natural barriers of the ocean provided the isolation that was essential to the evolution of Sri Lanka‘s unique species and ecosystems. In less than two centuries, these barriers have been rendered ineffective, because of an increased global trade that enables weed species to travel vast distances. Invasion by new alien species, and expanding infestations of existing invasives, are both major threats to biological diversity, second only to habitat degradation and losses, which occurs as a result of increasing population pressure in countries like Sri Lanka. Sri Lanka (earlier known as ‗Ceylon‘) is an ancient hydrological, rice-based civilization, dating back to more than 2500 years. During the last few centuries of colonial rule, plantation-scale agriculture took hold in the island – firstly, coffee and tea, and then, rubber, coconut and cinnamon plantations. Such a historical background provided Sri Lankan farmers with a sound tactical knowledge of how to manage weeds. Nevertheless, the new threats posed by a host of invasive species, and their increased abundance, have put pressures on the island‘s biodiversity and agricultural productivity. In the fight against weeds, a nation-wide planning framework is now required to coordinate and enhance the weed management efforts of the community, industry and government. During the past three years, or so, Sri Lanka Council for Agricultural Research Policy (CARP) gave leadership to develop a National Weed Strategy (NWS), following a ‗whole- of-government‘ approach, with input from government departments, research institutes, Universities, industry and the community. The objective of this paper is to present an overview of this national approach undertaken in Sri Lanka, and to discuss some issues that may enlighten other Asia-Pacific countries, which are tackling similar problems. Major weeds of concern Sixteen weeds of ‗National Significance‘ have been identified (Table 1), based on the scientific information available and the research by Departments of Agriculture and Export Agriculture, Research Institutes (Tea, Rubber, Coconut, Sugarcane), and Universities. The list includes major weeds of rice agriculture, waterways and plantation crops. As an ancient hydrological civilization, the island is dotted with thousands of inland lakes (or ‗tanks‘), which furnish water, primarly for a rice-based agriculture. These lakes and major rivers are inter-connected by irrigation networks, some of which are ancient. Inadequate management of waterways, over the years, has led to sedimentation and 117 23rd Asian-Pacific Weed Science Society Conference The Sebel Cairns, 26-29 September 2011 significant aquatic weed problems. Aquatic weeds reduce the flow of water, leading to inefficient irrigation. They reduce the habitat for aquaculture, cause water loss through evaporation; and provide breeding grounds for mosquitoes, including malaria and dengue. Major aquatic weeds of Sri Lanka include Water Hyacinth, Salvinia, Ipomoea aquatica Forssk., Hydrilla [Hydrilla verticillata (L. f.) Royle] and Myriophyllum L. spp. Infestations of Primrose Willows - Ludwigia peruviana (L.) Hara and L. octovalvis (Jacq.) Raven, are dominant in abandoned rice-fields, reclaimed marshlands and drainage canals, while L. decurrens Walt. and L. hyssopifolia (G. Don) Exell, are major rice-field weeds. Other major rice-field weeds in Sri Lanka include grasses, such as Echinochloa crusgalli; Ischaemum rugosum Salisb., Isachne globosa (Thunb.) O. Ktze and Leptochloa chinensis; various sedges, such as Cyperus iria L.; C. haspan L., Fimbristylis miliacea Vahl.; and many broad-leaved species, including Primrose Willows (Chandrasena, 1990). New agricultural and environmental weed problems that are causing great concern in Sri Lanka include various kinds of ‗Weedy Rice‘ (which are hybrids), Alligator Weed (Alternanthera philoxeroides), Mimosa pigra, Parthenium hysterophorus (Bambaradeniya et al., 2001; Marambe, et al., 2001) and Austroeupatorium inulifolium. Among new aquatic weed threats, two escapees from the aquarium trade - Mayaca fluviatilis and Ludwigia sedioides have now spread at least in one district (Yakandawala and Yakandawal, 2007). Table 1. Sri Lanka‘s Weeds of National Significance (Source: CARP, 2008) Common Name Botanical Name Habitat/Crop affected most Madeira Vine 1. Anredera cordifolia (Ten.) Steenis Tea plantations Siam Weed 2. Chromalaena odorata (L.) King & Robbins Coconut, Cinnamon plantations Dodder 3. Cuscuta campestris Yunck. All plantations; derelict lands Purple Nutsedge 4. Cyperus rotundus L. Rice agro-ecosystem Barnyard Grass 5. Echinochloa crusgalli (L.) Beauv Rice agro-ecosystem Water Hyacinth 6. Eichhornia crassipes (Mart.) Solms Irrigation tanks; drainage networks Cogongrass 7. Imperata cylindrica (L.) Beauv Tea plantations Lantana 8. Lantana camara L. National parks; derelict lands Red Sprangletop 9. Leptochloa chinensis (L.) Nees Rice agro-ecosystem Chinese Creeper 10. Mikania micrantha Kunth Rubber plantations Giant Mimosa 11. Mimosa pigra L. Riverbanks Congress Weed 12. Parthenium hysterophorus L. Fallow fields, marshy areas Guinea Grass 13. Panicum maximum Jacq. National parks; roadsides Mission Grass 14. Pennisetum polystachyon (L.) Schult. Roadsides; national parks Giant Salvinia 15 Salvinia molesta D.S. Mitchell Irrigation tanks, network; rice-fields Getakola 16. Spermacoce hispida L. Tea, rubber, coconut, plantations Sri Lanka’s national weed strategy The Sri Lanka National Weeds Strategy (NWS) 2009-2014 was developed as a 5-year planning framework for improved management of weeds across the country. This strategy, largely based on the Australian model, has three broad goals and several objectives under each goal (Table 2). The primary goals are to: (1) Prevent introduction, entry and
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