Spatio-temporal Distribution Pattern of New Biotypes of Weedy Rice (Oryza sativa L.) in Selangor North-West Project, Malaysia

Abstract

of infestation and prevalence of dominant NBWR accessions registered both season-and farm-block mediated differences. Most accessions showed VMR >1 thus indicative of having a clump or clustered spatial distribution, as exemplified by Acc3, Acc4, Acc7, Acc8 and Acc12 in all farm blocks throughout three seasons. Some accessions have either random or uniform distribution in a few farm blocks. The Acc8 has the highest population counts based on important value index, followed by Acc12, and both were the most dominant accession while Sawah Sempadan was the worst farm block infested by NBWR compared to other farm blocks. These results were discussed in relation with the current agronomic and weed management practices, water availability and extension services in the granary.

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“…The implementation of direct seeding practice as a shift from laborious transplanting was a spark of weedy rice infestation in most rice granaries and farms in Malaysia (Azmi et al 2000;Baki and Shakirin, 2010). The integrated approach (Table 1) includes straw burning, shallow tillage, preemergence herbicide application, multiple tillage (dry and wet), sowing of pre-germinated seeds, flooding, ditches/levees control, hand-weeding, panicle roguing and weed-free crop (Azmi and Abdullah, 1998;Azmi et al 2000;Azmi and Karim, 2008).…”

“…In the early 90's to middle 2000's, most farmers practiced hand-weeding in their direct-seeded farm by roguing the weedy rice (Azmi and Karim, 2008). Since the weed was generally taller in stature than cultivated varieties, farmers can easily identify them and slashing the weedy rice panicles before harvest (Baki, 2010;Baki and Shakirin, 2010). Selective weeding was effectively controlling weedy rice infestation during this period especially in the Sekinchan area, but this practice was found impractical especially in broadcast-seeded rice (Azmi and Karim, 2008), resulting in accidental damage of cultivated rice during the process.…”

“…To make it worse, the recent report on the emergence of new biotypes of weedy rice (NBWRs) which morphologically mimics commercial cultivated varieties (i.e. MR220 and MR219) especially in height, making weedy rice almost unrecognizable (Mispan, 2008, Baki andShakirin, 2010;Mispan et al 2015) and caused hand-weeding impossible. Although the NBWRs infestation was still in the early stages, their distribution pattern was found to be like the previously weedy rice emergence in Malaysia (Baki and Shakirin, 2010).…”

“…However, the infestation tremendously increased in 2005 where 91 per cent of rice fields were infested, with 88 per cent accounted of at least 10 per cent infestation Baki, 2006). Spatial distribution pattern of weedy rice in Malaysia generally showed a uniform but restricted distribution with recorded variance-to-mean ratio and Lloyd's patchiness index values less than one Baki and Shakirin, 2010). Infestation of weedy rice caused severe rice production loss due to the competitive nature of weedy rice against cultivated rice (Diarra et al 1985;Delouche et al 2007;Chauhan, 2013).…”

“…Entering the millennium, more than 50 per cent of rice granaries in Tanjung Karang, Selangor and Besut, Terengganu were reported to be infested with weedy rice (Azmi et al 2000;Anuar et al 2014), while in Muda, Kedah weedy rice was dominant with registered infestation level ranging from less than 10 per cent to more than 20 per cent coverage (Azmi et al 2005a,b). The infestation was also temporally dynamic in recent years especially in states of Kedah, Perak and Selangor (Baki and Shakirin, 2010). The weedy rice infestation was not significant in 1995 but it was skyrocketed in 1996 with more than 19,900 ha of rice farms were infested in Peninsular…”