Invasive apple snails in Malaysia H. Yahaya1, A. Badrulhadza2, A. Sivapragasam3, M. Nordin4, M.N. Muhamad Hisham5 and H. Misrudin4 1Paddy and Rice Research Centre, Malaysian Agricultural Research and Development Institute (MARDI), Telong, 16310 Bachok, Kelantan, Malaysia. Email: yahayahussain@ gmail.com, [email protected] (Current address: Lot 241 Kampung Renik Banggu, Jalan Bukit Marak, 16150, Kota Bharu, Kelantan) 2Crop and Soil Science Research Centre, Malaysian Agricultural Research and Development Institute (MARDI), 43400, Serdang, Selangor, Malaysia. Email: bhadza@ mardi.gov.my 3CABI South East Asia, Building A 19, MARDI 43400 Serdang, Selangor, Malaysia. Email: [email protected] 4Crop Protection and Plant Quarantine Division, Department of Agriculture, Kuala Lumpur, Malaysia. Email: [email protected], [email protected] 5Muda Agricultural Development Authority, Alor Setar, Kedah, Malaysia. Email [email protected] Abstract South American apple snails, Pomacea spp., classified as quarantine pests in Malaysia, were first detected in Malaysia in 1991. However, it took almost 10 years before they developed into one of the major pests of rice in the country. Since then, they have spread to almost all the rice areas in Malaysia. Since their detection, continuous control, containment and eradication programmes and research activities have been conducted by various government agricultural agencies involved in rice production. The efforts have been successful in reducing crop damage by the snails but have failed to arrest their dispersal to new areas. Since 2002, the snails have infested almost 20,000 ha of rice growing areas (2008 data) and have threatened the livelihoods of farmers. In 2010, costs associated with apple snail damage were estimated as RM 82 million (US $28 million). Various management strategies involving the use of chemical, cultural, physical and biological control techniques have been developed and extended to the farmers. Success in controlling the snail infestation has been achieved but at higher crop production cost. 169 This contribution discusses the impacts of apple snail infestation in Malaysia, the various actions that have been developed and undertaken to manage the infestations, and the future outlook for the impact on rice production. Additional keywords: Ampullariidae, integrated management strategies, Mollusca, Pomacea, rice Introduction Malaysia has an estimated wetland rice area of 350,357 ha, of which 262,809 ha is in Peninsular Malaysia, 63,064 ha in Sarawak and 24,524 ha in Sabah (Anonymous, 2012). Wetland rice constitutes about 85 % of the total rice area in the country, while the remaining 15 % is upland rice. In Peninsular Malaysia, 76 % of the wetland rice area has extensive irrigation and drainage facilities, while in Sabah and Sarawak only 15 % of the area is irrigated. About 72 % of rice production comes from the eight granary areas, all in Peninsular Malaysia. Two rice crops are cultivated per year in the granary areas, with the main season crop sown in August for a February harvest and the off-season crop sown in May for an October harvest. The national average yield for the main season crop of 2010 (combined granary and non-granary areas) was 3.9 tons/ha, while the average yield from the eight granary areas was 4.6 tons/ha (Anonymous, 2012). Currently, local rice production contributes about 72 % of total consumption, with the rest imported from other countries in the region. It is government policy to ensure that the country’s rice output is maintained at 65 % of current need and increased to 90 % by 2020. Rice is cultivated mainly by smallholders with an average farm size of 1.06 ha. Rice production in Malaysia is threatened by an acute labour shortage, leaving only the elderly to tend the crop. Furthermore, rice cultivation is not cost effective compared with other crops such as tobacco and melon. The rice growing area in Malaysia is not expected to increase; it is more likely that it will give way to human settlement and industrial development. Planted rice areas will also see a declining trend with the passing of the old generation of farmers. To maintain the current production capacity, productivity has to be increased. Some farmers in the state of Selangor have even obtained yields exceeding 10 tons/ha. To reach higher productivity, yield-limiting factors such as diseases and pest infestations have to be reduced. The introduction and current infestation of apple snails is one of the main threats to rice production in Malaysia. The effort to bridge the gap between 170 BIOLOGY AND MANAGEMENT OF INVASIVE APPLE SNAILS the current average yield of 3.9 tons/ha and the targeted sustainable yield of 7-8 tons/ha might be jeopardized if effective control measures are not implemented. Current status of apple snail infestation Apple snail infestations have spread to almost all of the rice granary and non-granary areas of Malaysia. The total area infested increased from 17,399 ha of rice in 2004 to almost 20,704 ha in late 2008. Estimated yield losses (in tons) caused by apple snails in rice granary and non-granary areas in the main season of 2009 are shown in Tables 1 and 2. Currently, the snails are present in all states except Johor in the south of Peninsular Malaysia. They have now become a key pest of rice in Malaysia (Yahaya et al., 2010). Although the authorities have undertaken various control measures, the snails have been found spreading continuously to new areas. In 2010, costs associated with apple snail damage were estimated as RM 82 million (US $28 million). Since 2009, following intervention measures, the data suggest a fluctuating but stable area of around 2,500 ha from 2009 until 2012 (Fig. 1). The total infested area in off-season 2015 was about 1939 ha. Table 1. Estimated yield losses caused by apple snails in rice granary areas in the main season of 2009. Cultivated area Yield losses Value Granary Area (ha) (ton) (RM) MADA1 96,547 10,977 11,807,185 KADA2 28,137 18,178 19,995,910 IADA3 Kerian Sungai Manik 26,846 918 1,009,470 IADA Barat Laut Selangor 18,729 376 526,540 IADA P. Pinang 10,305 1,029 1,142,190 IADA Seberang Perak 7,272 5,148 6,692,400 IADA Ketara 4,923 0 0 IADA Kemasin Semerak 4,520 56 56,000 Total 197,279 36,682 41,229,695 1 Muda Agricultural Development Authority 2 Kemubu Agricultural Development Authority 3 Integrated Agricultural Development Authority INVASIVE APPLE SNAILS IN MALAYSIA 171 Table 2. Estimated yield losses caused by apple snails in rice in non-granary areas in the main season of 2009 in the various states of Malaysia. Cultivated area Yield losses Area Value (RM) (ha) (ton) Kedah 30,488 2,747 1,442,043 Johor 1,228 0 0 Kelantan 10,164 19 19,200 Melaka 943 3 3,300 N.sembilan 298 8 6,160 Pahang 4,404 3 3,300 Perak 6,178 328 360,800 Perlis 7,403 262 288,200 Pulau pinang 2,477 236 259,600 *Selangor - - - Terengganu 3,842 0 0 TOTAL 67,425 3,606 2,382,603 *Data not available The distribution of apple snails, however, does not necessarily correlate with the damage they cause. In some areas, such as in Perak, where more than 10,000 ha of rice were infested, damage to rice seedlings was minimal and mainly confined to poorly irrigated areas where water could not be drained off during the first 10 days of rice cultivation (Fig. 2). In other areas, such as in Kelantan, the total area infested was comparatively small, but damage could be quite extensive because of the recent introduction of apple snails and the indifferent attitude of the farmers towards the threat posed by them. The impact of apple snail infestation is more serious in Malaysia than elsewhere because direct seeding is practiced by the majority of rice farmers to offset labour constraints. This practice exposes the vulnerable rice seedlings to attack. It is well known that the critical stage during which damage can be severe is basically confined to the first month after sowing, after which the rice plants are not adversely affected. 172 BIOLOGY AND MANAGEMENT OF INVASIVE APPLE SNAILS Fig. 1. Infestations by apple snails from 2009 to 2012. (Source: Palasupramaniam, DOA, Malaysia, 2013, pers. comm.). Fig. 2. Damage is severe when the field cannot be drained before pre-germinated seed is broadcast. (Photo: H. Yahaya) INVASIVE APPLE SNAILS IN MALAYSIA 173 Review of research and training activities Research Although apple snails were first detected in rice fields in Malaysia as early as 1991, no substantial damage to rice crops was reported until the late 1990s. The species present in Malaysia were identified asPomacea canaliculata and P. insularum (which has now been synonymized with P. maculata; Hayes et al., 2012). During the early phases of apple snail detection, containment and eradication programs were conducted using tea seed cake (TSC) and other molluscicides, based on experiences reported from other countries (Chang, 1992; Fouzi et al., 1992). Molluscicide screening trials were conducted, and copper sulphate and salt water were found effective in controlling the snails. These trial results were used as the basis for eradicating an infestation in Kampung Pengkalan Semeling in Kuala Kedah by inundating the infested rice field with sea water followed by subsequent flushing with fresh water (Esa et al., 1992). The attempt was successful in eradicating the snails in this locality primarily because of its close proximity to the sea and the availability of a fresh water supply nearby. Research was also conducted on integrated management of apple snails, involving cultural, biological and chemical control (Teo, 1999a). To facilitate handpicking of snails by farmers, trials were conducted to evaluate various plant attractants as baits, with the leaves of papaya, sweet potato, tapioca (Fig.