Global distribution of rice weeds – A review

Crop Protection 80 (2016) 73e86

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Crop Protection journal homepage: www.elsevier.com/locate/cropro

Review

Global distribution of rice weeds e A review Hansjoerg Kraehmer a, *, Khawar Jabran b, Husrev Mennan c, Bhagirath Singh Chauhan d a

Kantstrasse 20, D-65719 Hofheim, Germany Department of Plant Protection, Adnan Menderes University Aydin, Turkey c Department of Plant Protection, Ondokuz Mayis University, Samsun, Turkey d The Centre for Plant Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Toowoomba, Queensland 4350, Australia b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 3 August 2015 Received in revised form 22 October 2015 Accepted 27 October 2015 Available online xxx

This review provides an overview on the most common rice weed species of the world. It shows that a few generalists have established in rice independent from sites, crop management systems, and local climatic conditions. Cosmopolitan weeds are even constant elements where rice cultivation started just a century ago. Local differences may be explained by cultivation methods, growing seasons, or special weed management. Some general changes in weed spectra have been observed globally in recent years. Weedy rice (Oryza sativa L.) and herbicide resistance have become general global problems within the last decades. Some global key weed genera such as Echinochloa, Cyperus, Scirpus, or Fimbristylis species are, however, still dominating rice fields despite the decade long use of well performing herbicides. On the other side, general species shifts as a result of resistance have not been observed yet. Leptochloa species started to become major problems in Asia in the end of the last century and now in Europe also. Several modern herbicides allow the control of perennial weeds, such as Cyperus rotundus L. or Eleocharis kuroguwai Ohwi which makes them no longer serious threats. Some genera in rice such as Echinochloa and Oryza (weedy rice) are characterized by an enormous germplasm variability which makes species definitions difficult. The fact that weeds in rice have to adapt to wet or aquatic conditions reduces the biodiversity range in comparison to other arable crops. Water management has a considerable impact on weed spectra. The increase of rice acreages with reduced irrigation may end up in higher weed infestations. Long term results of weed surveys in rice as they exist for other crops are, however, not available. This makes predictions on biodiversity changes in this crop quite difficult. © 2015 Elsevier Ltd. All rights reserved.

Keywords: Weed distribution Evolution of weed populations Biodiversity Global rice weed spectra

Contents 1. 2. 3. 4.

5.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Studies considered for the review article . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Rice production systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Weeds grouped according to taxonomy and weed complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.1. Weedy rice (Table 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.2. The Echinochloa complex (Table 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 4.3. The Cyperus complex (Table 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.4. Club rushes and spike rushes (Table 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.5. Other monocot weeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 4.5.1. Grasses (Table 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 4.5.2. Broadleaved monocots (Table 7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 4.6. Dicot weeds (Table 8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Weeds specific to rice growing areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

* Corresponding author. Kantstrasse 20, 65719 Hofheim, Germany. E-mail address: [email protected] (H. Kraehmer). http://dx.doi.org/10.1016/j.cropro.2015.10.027 0261-2194/© 2015 Elsevier Ltd. All rights reserved.

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6.

7.

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Conclusions on generalists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.1. Which weeds are the most common and hard to control ones? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.2. How long does it take for generalists to establish? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 6.3. Which selection principles lead to regional weed infestation differences? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

1. Introduction Biodiversity in agriculture has become a global political issue within recent years. The United Nations General Assembly defined the time span of 2011e2020 as the Decade of Biodiversity (Resolution 65/161). The reason for this international interest in biodiversity is the global change and reduction of species caused by industrialisation. Biodiversity considerations apply to agriculture and they do not only refer to crops but to weeds also. Rice, as a crop, is either an aquatic or wetland plant that requires relatively large amounts of water for its development compared with other crops. Even rice grown on dry soils requires high amounts of rain. In consequence, the flora accompanying rice is usually adapted to wetland or aquatic conditions also. There are a few articles referring to biodiversity in rice fields. Yamada et al. (2011), for instance, showed that the floristic composition of rice paddy fields may vary to quite an extent and that landscape may have a major influence on biodiversity. Wan et al. (2012) stress the influence of fertilizers on weed community characteristics in China. Lal et al. (2014) published data for a similar approach in India. Modern management practices seem to have contributed to shifts in rice weed associations globally. A thorough analysis of weed management in direct-seeded rice was published by Rao et al. (2007). It demonstrates weed shifts and specific weed spectra caused by different rice cultivation methods. The authors stressed that lowland direct-seeded rice in Asia shows a greater diversity in Asia than transplanted rice. Dominant rice weeds have apparently established all over the world and prevent the establishment of local and rare species. Rice as one of the oldest crops grown by man has a short history in some areas of the world. In California and Australia, for example, rice cropping has started in the last century only (Grist, 1965). In both rice growing areas, a considerable number of common weed species are found (McIntyre and Barrett, 1985). The explanation is simple: the major source of Australian rice seeds had Californian origin. Almost one-half of the alien species in Australian rice is native to America. This means that rice weeds have found their new habitats often with contaminated crop seeds. Irrigation water is usually coming from channels and ditches. Many rice weeds grow in and along these water ways and are a rich source for the infestation of rice fields. Holm et al. (1977) published maps more than three decades ago (1977), demonstrating the worldwide distribution of major rice weeds. It seems, however, as if some weed problems such as weedy rice (Oryza sp., see 4.1) were not addressed those days. Caton et al. (1999) stressed that despite decades of herbicides, weeds continued to be a major problem in rice. With herbicide resistance, the problem even becomes worse. This is why we ask here which factors actually drive weed infestation in rice fields and determine the number of species in a field from a global perspective. The purpose of this review is to analyse the present global weed situation and to evaluate and clarify. - which generalists are dominant in rice fields today globally

- which changes can be observed compared with the situation 30 years ago - how crop management influences the composition of weed assemblies in rice - which rice weeds must be regarded as specific for selected rice growing areas.

2. Studies considered for the review article Most of our results are based on literature searches for the last 20 years (1994e2014), for example, by using www.scopus.com. We included field studies, in which weeds had a chance to grow under different conditions. Studies on surveys of rice fields were also considered. In addition, we compared these results with our own observations in more than 20 years of field trials in different parts of the world. The International Rice Research Institute (IRRI) has published status reports on the weed infestation of rice fields in different parts of the world over several decades. These documents allow an analysis of changes in weed spectra over time, especially when comparing the documented data with most recent papers published in different scientific journals. In the first instance, we have restricted our analysis to a few topics only. We list primarily weeds occurring within the growing crop and not those which can be found before planting or after harvest. We restrict this article also to higher, non-floating plants only, that is, we will not discuss ferns, such as Azolla- and Salvinia species. The tables in this article contain mostly single, usually most recent references for selected countries and management regimes in order to provide an indication of the range of environments and the global distribution of single weed species. The primary pool consisted of 129 references listed in Table 1. Of course, our initial literature research resulted in far more citations. This review, however, does not aim for completeness and for a mere listing of all articles written on rice weeds ever. There are many standard compilations describing the occurrence of weeds in rice such as those of extension services and universities, for example, by Webster (2014) or IRRI handbooks for Asia (for example, by Ampong-Nyarko and De Datta, 1991 or Jena and Hardy, 2012). One approach for South and Southeast Asia was that of Moody (1989) 25 years ago. Many overview articles describe weed spectra of single countries such as Japan (for example, Shibayama, 2001). Attempts to provide global overviews on dominating rice weeds are, however, quite rare so far. 3. Rice production systems Rice has been grown in Asia already in Neolithic times. The genus Oryza consists of a large complex of more than 20 species. Oryza sativa L. is presumably derived from its wild ancestor, Oryza rufipogon L. Domestication of Asian rice in the Neolithic era started at least at two domestication centres: one in South China for japonica rice and another in the southwest of the Himalayan mountain range for indica rice (Yu et al. 2011; Vaughan et al., 2005; Hoshikawa, 1989). Oryza glaberrima Steud. is typical of Africa; it is

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Table 1 Literature for the categorisation of rice weed complexes. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Adigun et al., 2005 Ahmed and Chauhan, 2014 Ahmed et al., 2014 Altop and Mennan, 2011 Ampong-Nyarko and De Datta 1991 Andres et al., 2012 Andres et al., 2013a Andres et al., 2013b Anwar et al., 2010 Anwar et al., 2013 Baki et al., 2000 Baloch et al., 2005 Begum et al., 2005 Benvenuti et al., 2004 Bhurer et al., 2013 Biswas et al., 2005 Braverman, 1995 Buehring et al., 2001 Burgos et al., 2008 Busi et al., 2006 Calha et al., 2007 Cao et al., 2007 Carretero, 1986 Casimero et al., 2006 Chadhar et al., 2014 Chapagain et al., 2011 Chauhan, 2013a,b Chauhan and Abugho, 2013 Chauhan and Johnson, 2011a Chauhan and Johnson, 2011b ~ a, 2012 Chauhan and Open Chauhan et al., 2014 Chhokar et al., 2014 Chin, 2001 Dai et al., 2014 Danquah et al., 2002 De Sousa et al., 2012 Dilipkumar et al., 2012 Ekeleme et al., 2009 Ferrero and Tinarelli, 2008 Florez et al., 1999 Fofana and Rauber, 2000 Fogliatto et al., 2011

44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

Galhano et al., 2011 Gealy et al., 2014 Hakim et al., 2013 Hussain et al., 2008 Hussain et al., 2011 Hwang et al., 2006 Imeokparia, 1994 Jacob and Syriac, 2005 Johnson and Kent, 2002 Johnson et al., 2004 Juraimi et al., 2009 Kabir et al., 2008 Kaloumenos et al., 2013a,b Kamoshita et al., 2014 Karim et al., 2004 Kent and Johnson, 2001 Khaliq et al., 2013 Khanh et al., 2006 Kim and Ha, 2005 Koger et al., 2006 Krupnik et al., 2012 Kumalasari, 2014 Kuroda et al., 2006 Lal et al., 2014 Li et al., 2012 Lundy et al., 2014 Mahajan et al., 2012 Mahajan et al., 2014 Mandal et al., 2013 Mann et al., 2007 McIntyre and Barrett, 1985 Men et al., 1999 Mennan and Kaya-Altop, 2012 Midya et al., 2005 Moody, 1989 Moon et al., 2014 Mohtisham et al., 2013 Motlagh and Sharifi, 2011 Moukoumbi et al., 2011 Mudge et al., 2005 Mukherjee and Singh, 2005 Norsworthy et al., 2013 Ntanos and Koutroubas, 2000

derived from Oryza barthii A.Chev. (Sakagami et al. 2013) and was apparently domesticated in the Niger Delta already 3500 years ago (Semon et al. 2005). Modern African rice varieties are often crosses between O. sativa and O. glaberrima (Somado et al. 2008). Today, rice is grown in many tropical and subtropical regions of the earth (Fig. 1). The global cultivated rice area amounts to around 163 million ha, thereof 145.3 million ha in Asia, 10.5 million in Africa, 4.8 million ha in Latin America, 1.1 million in North America, 0.7 million ha in Europe, 0.3 million ha in Central America, and 0.1 million ha in Australia (FAOSTAT, 2012, http://faostat.fao.org/site/ 567/default.aspx#ancor). It is impossible to explain the occurrence of rice weeds without describing rice production systems. We summarise here, for instance, rice production systems, in which certain weeds were found in different countries. Rao et al. (2007) defined different crop management systems. Here, we follow their terminology and use some abbreviations throughout this review. First, transplanted (TP) and direct-seeded rice (DSR) are two major cultivation categories. For TP rice, seedlings are grown first in seed beds and transplanted on a field either by hand or machines. They are usually transplanted on a conventionally puddled and flooded field. The field is kept inundated for a major part of the crop season. The layer of water serves the suppression of weeds and to achieve certain ecological benefits such as beneficial animals living in the water. This type of rice production is considered expensive and non-sustainable in

87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129

Osca, 2013 Pacanoski and Glatkova, 2009 Phuong et al., 2005 Pinke et al., 2014 Pittelkow et al., 2012 Pons, 1982 Prathepha, 2009 Prathepha, 2011 Pratley et al., 2004 Raj et al., 2013 Rao et al., 2007 Rashid et al., 2012 Ratnasekera et al., 2014 Rodenburg et al., 2014 Roder, 2006 Roham et al., 2014 Saito and Futakuchi, 2014 Saito et al., 2010 Sanusan et al., 2010 Shen et al., 2013 Shibayama, 2001 Silva and Durigan, 2006 Singh et al., 2013 Singh et al., 2014 Sparacino et al., 1996 Sparacino et al., 2007 Strand, 2013 Street et al., 1995 Tan et al., 2000 Tomita et al., 2003 Toure et al., 2014 Towa et al., 2013 Tuong et al., 2000 Turki and Sheded, 2002 Vasconcelos et al., 1999 Viggiani et al., 2003 Wan et al., 2012 Watanabe, 2011 Webster, 2014 Weerakoon et al., 2011 Xuan et al., 2001 Yamada et al., 2011 Yamasue, 2001

many countries today because of high water and labour needs. DSR can be subdivided into three categories: a) Wet-seeded rice (WSR) Wet-seeded rice is sown on a wet soil. The soil is kept wet for the major part of the growing season. Seed beds have to be levelled. Spatial variation in water regimes can impact seed germination. This management system is applied in some parts of Asia, Africa, and Latin America. b) Water seeded or flooded rice (FR) Flooding of fields before sowing is practiced mainly in Australia, the USA, and in European countries. Sowing of pre-germinated seed by aeroplane is common in Australia and California. In Europe, presoaked or pre-germinated seed is usually broadcast on standing water with a centrifugal spreader that can also be used for the application of fertilizers. In some areas, aerial seeding is also common. c) Dry direct-seeded rice (DDSR) Dry direct-seeded rice is sown directly on a dry soil. Later the crop is flooded or irrigated, depending on water availability. The

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H. Kraehmer et al. / Crop Protection 80 (2016) 73e86

Fig. 1. Overview on rice growing areas in the world.

term upland rice (UR) usually refers to dry-seeded, rainfed uplands. Upland rice is a subsistence form of rice farming in most cases. The rice seeds are planted directly on dry soil, the crop moisture needs are generally met through rainfall water. This rice production system is especially important for Africa, a large part of Brazil, and several parts of Asia. d) Lowland rice (LLR) is another term used for rainfed or irrigated rice (DSI) in lowlands. Lowland irrigated rice is sown either by direct seeding or transplanting of seedlings. After planting, the crop is irrigated. In some rice growing areas, the soil is flushed for the rice and weeds to germinate but not flooded. Herbicides are applied by tractors in some rice growing areas and the field is flooded then a few days later. e) Aerobic rice (AR) is a new alternative to high water amount consuming rice management systems. New rice varieties were developed at the end of the 20th century in China which guarantee high yields in non-puddled soils without flood irrigation (Huaqi et al., 2002). The first varieties were released under the name Han Dao, for example, Han Dao 277 and Han Dao 297. This type of rice is called aerobic rice. Today, aerobic rice is kept un-flooded throughout the growing season. The crop is sown either by directly planting seeds on a well prepared field, or transplanting rice seedlings on a wet soil. However, the direct planting of seeds is the most widely adapted way of growing aerobic rice. Although aerobic rice resembles upland rice to a great extent, it is provided with irrigation water, and higher yields are obtained in aerobic rice than in upland rice. Aerobic rice nowadays is being followed in many of the rice growing countries of Asia, owing to lower water and labour needs of this method compared with the conventional transplanting method.

Crop management and crop rotation have a considerable influence on weed infestation as could be shown for different areas in the world (for example, for the Indo-Gangetic Plains by Chauhan et al. 2012; for Sub-Saharan areas by Kent et al. 2001 or Johnson and Kent, 2002). Continuous rice cropping over several seasons is quite common in areas where complicated drainage and dam or levee systems are produced to hold water back for paddies. This situation is different from aerobic, rainfed, or upland rice where rice is often part of crop rotation systems. The scale in Fig. 1 does not allow a clear distinction between rice cropping systems. It shows, however, that rice is primarily grown in areas with tropical and subtropical climates, that is, between 45
northern latitude (Po valley in Italy) and 35
southern latitude (New South Wales, Australia). One can recognize the large upland rice area in northern Brazil. Many rainfed upland rice and irrigated rice areas in Asia overlap, but they are not clearly distinguished in Fig. 1. 4. Weeds grouped according to taxonomy and weed complexes 4.1. Weedy rice (Table 2) Weedy rice is a complex of taxonomically not well defined Oryza species, hybrids and special biotypes. In some Asian countries, wild rice species such as Oryza rufipogon Griff. and Oryza nivara S.D.Sharma & Shastry sometimes directly compete with cultivated rice (e.g., Kuroda et al. 2006). In other areas, weedy rice biotypes derived from O. rufipogon and O. sativa are dominant such as red rice in the USA which is named after its red pericarp (Burgos et al., 2008). Some scientists define weedy rice as Oryza sativa f. spontanea (e.g., Prathepha, 2011) but this designation has no botanical substantiation. Others call it just O. sativa (e.g., Zhang et al., 2014). Sophisticated large scale genome studies were carried out to

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Table 2 Weedy rice reported from various rice growing regions of the world. Only selected, most recent references are listed. Country

Rice system (- no distinction)

Reference

Brazil

FR UR TP AR, TP (weedy rice had poor performance in DSR) DDSR TP, FR FR AR FR TP, UR AR (but absent in TP in the same study) TP AR FR TP, DDSR AR AR TP, AR DDSR FR AR TP, DDSR WSR

(Andres et al., 2013b) (Goulart et al., 2014) (Kamoshita et al., 2014) (Cao et al., 2007) (Shen et al., 2013) (Andres et al., 2012) (Pinke et al., 2014) (Singh et al., 2013) (Fogliatto et al., 2011) (Watanabe, 2011) (Kim and Ha, 2005) (Prathepha, 2011) (Chauhan, 2013b) (Hussain et al., 2011) (Karim et al., 2004) (Chauhan and Johnson, 2011b) (Chauhan, 2013b) (Ratnasekera et al., 2014) (Prathepha, 2009) (Burgos et al., 2008) (Chauhan, 2013b) (Chin, 2001) (Chauhan et al., 2014)

Cambodia China

Hungary India Italy Japan Korea Laos Malaysia

Philippines Sri Lanka Thailand USA Vietnam

UR ¼ Upland rice; LLI ¼ Lowland irrigated rice; TP ¼ Transplanted rice; AR ¼ Aerobic rice; FR ¼ Flooded rice; DDSR ¼ Dry direct-seeded rice; WSR ¼ Wetseeded rice; DSI ¼ Direct-seeded irrigated rice; DSLL ¼ Direct-seeded lowland.

characterize all sorts of collected wild and weedy rice biotypes with varying germplasms (e.g., by Vaughan et al. 2005). Studies describing weedy rice in various rice growing areas of the world are summarised in Table 2. Weedy rice was reported from many countries such as Brazil, Cambodia, China, Hungary, India, Italy, Japan, Korea, Laos, Malaysia, Philippines, Sri Lanka, USA, and Vietnam (Chauhan, 2013b,c; Ziska et al. 2015). Several overviews on weedy rice have been published over the last decades, for example, by IRRI publications such as the Proceedings on “Wild and weedy rice in rice ecosystems in Asia” (ed. by Baki et al. 2000). The book “Crop ferality and volunteerism” edited by Gressel (2005) devotes several chapters to the occurrence and characterisation of weedy rice. Chauhan (2013b,c) summarizes strategies for the management of weedy rice. Unfortunately, surveys based on country summaries are often not precise enough. Weedy/red rice is a problem in many areas of the USA but for instance not in California and in some parts of the world where transplanted rice is cultivated (e.g., Korea). One reason for the worldwide increase of areas infested with weedy rice are limited control options and another is the shift from flooded/ transplanted to direct-seeded rice and contaminated seed (Ziska et al. 2015). The recent introduction of imidazolinone-tolerant rice varieties, however, offers now tools to control it efficiently in many cases (Sudianto et al., 2013a,b). Unfortunately, imidazolinone-resistant weedy or red rice has become a problem within a short time after the introduction of this technology. This setback will be discussed under 6.3 below.

4.2. The Echinochloa complex (Table 3) Unfortunately, the identification of Echinochloa species is not easy and the scientific literature is full of different or synonymously used species names without clear and identical distinction criteria. This fact makes it hard to clarify which Echinochloa species is actually occurring where. A few examples explaining the confusing situation are mentioned here. The identification of Echinochloa species bases on morphological criteria primarily. De Wet et al. (1983) differentiate Echinochloa colona (L.) Link. from Echinochloa crus-galli (L.) P. Beauv. in having smaller spikelets with

membranaceous rather than chartaceous glumes. They make clear that sometimes E. colona is described as an awnless species in contrast to E. crus-galli. It is, however, obvious that awnless biotypes also exist within the species E. crus-galli. Echinochloa oryzicola Table 3 Echinochloa complex recorded from various rice growing regions of the world.

Australia Bangladesh Brazil Cambodia China Colombia ^ te d'Ivoire Co Egypt Greece Hungary India Indonesia Italy Japan Korea Laos Macedonia Malaysia Nepal Pakistan Philippines Portugal Senegal Spain Sri Lanka Thailand Turkey USA Vietnam

ECHCG

ECHCO

x x x

x x x x x x x x

x

x x x x x x x x

ECHCR

ECHOR

ECHCV

ECHGL

ECHMA

x

x x

x x x

x x x

x

x

x x x x x x

X x x x x

x

x x x x x x

ECHCG ¼ E. crus-galli. ECHCO ¼ E. colona. ECHCR ¼ E. oryzicola. ECHOR ¼ E. oryzoides. ECHCV ¼ E. crus-pavonis. ECHGL ¼ E. glabrescens. ECHMA ¼ E. macrocarpa.

x

x

x x x

x x

x x x

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Vasing is often classified taxonomically as E. crus-galli var. oryzicola (Vasinger) Ohwi. Echinochloa oryzoides (Ard.) Fritsch is sometimes regarded as synonymous of Echinochloa phyllopogon (Stapf) Koss. (Hirosue et al., 2000). Other authors regard E. phyllopogon as identical with E. oryzicola (e.g., Iwakami et al., 2012). Echinochloa erecta (Pollacci) Pignatti is a species that is primarily mentioned in Italian literature (for example Sparacino et al., 2007 or Viggiani et al., 2003). Michael (1983), however, suspects that this species represents E. crus-galli ssp. hispidola and is actually a special form of E. phyllopogon. Echinochloa hispidula (Retz.) Nees ex Royle is regarded as synonymous with E. oryzoides (Ard.) Fritsch, E. oryzicola Vasinger, and E. phyllopogon (Stapf) Stapf ex Kossenko by the “world checklist of selected plant families” that is regularly updated by Kew Royal Botanic Gardens (http://apps.kew.org/wcsp/ namedetail.do?name_id¼410285, accessed on June 14, 2015); the only accepted name by this source for all these species is E. oryzoides (Ard.) Fritsch. On the other side, Volume 25 of The Flora of North America (edited by Barkworth et al., 2003) lists E. crus-galli, E. oryzoides, and E. oryzicola as separate species other than the Kew Royal Botanic Gardens classification. Echinochloa glabrescens Munro ex Hook.f. can be found synonymous with E. crus-galli var. formosensis Ohwi in literature (Michael, 1983). Another Echinochloa species described as a weed in rice is E. crus-pavonis (Kunth) Schult. syn E. crus-galli var. crus-pavonis (Kunth) Hitchc. The number of chromosome sets or polyploidy levels have been used in the past to differentiate between species and biotypes, for example, tetraploid and hexaploid forms (Aoki and Yamaguchi, 2009). In recent years, molecular biology tools such as RFLP (Restriction Fragment Length Polymorphism) analysis (Yasuda et al. 2002) or the analysis of noncoding regions of chloroplast DNA (Yamaguchi et al., 2005) served as further characterisation tools. As a result of the still confusing situation in the taxonomic classification of Echinochloa species, it has to be assumed that not all reports on Echinochloa species in rice fields deal with clearly defined species or biotypes. This is why we rather prefer talking about an Echinochloa complex here. We take, however, the species names in literature for granted in the first instance and apply sorting criteria based on names used in publications. In our literature search, E. crus-galli was the most prevalent Echinochloa species followed by E. colona (Table 2). Both weed species were reported from all around the world in rice growing countries. Also, these weeds were found to occupy all kinds of rice cultures including flooded, upland, transplanted, and aerobic rice and they can be problem weeds in many other crops also. E. colona seems to be more typical of tropical and sub-tropical areas. E. crusgalli seems to cover a wider range. It is also a common weed in temperate crops. Holm et al. (1977) reported it growing as far north as Denmark in Europe. Holm et al. (1977) indicated that E. crus-galli does not seem to be a problem in Africa. This may be true for SubSaharan Africa. In Egypt, it is, however, one of the dominant rice weed species (Ibrahim, 1989; Turki and Sheded, 2002). First AFLP (Amplified Fragment Length Polymorphism) and microsatellite studies proof that there is introgression of E. crus-galli into material that was once defined as E. crus-pavonis (Kunth) Schultes (Danquah et al., 2002). E. oryzicola Vasing. was the third most reported species after E. crus-galli and E. colona. This species was also reported from many parts in the world, mainly in the East Asian countries such as Japan, Korea, and Vietnam but also from the USA. E. glabrescens Munro ex Hook was mentioned in the Philippines and in Japan only. E. oryzoides was reported mainly from two countries, the USA and Turkey. De Wet et al. (1983) describes Echinochloa macrocarpa Vasinger as a Russian race of E. oryzoides. 4.3. The Cyperus complex (Table 4) Cyperus rotundus L., Cyperus iria L., and Cyperus difformis L. are

the most frequent Cyperus species reported in rice. They occur in all rice growing regions of the world. C. iria and C. difformis are typical annual rice weeds and generally noted in all kinds of rice cultivation systems. C. rotundus is a perennial weed and invasive to the Americas. It causes problems in all kinds of irrigated crops; Holm et al. (1977) already mention that this weed was reported to be a weed in 52 crops in 92 countries. Other important perennial sedge weeds found in rice are Cyperus esculentus L. and Cyperus serotinus Rottb. C. esculentus is a common weed in many crops such as maize, soybean, and cotton. It can be found in both aerobic and transplanted rice systems. C. serotinus is apparently restricted to rice. It is mainly growing in transplanted paddy rice of a few Asian countries such as Japan, Korea, and Vietnam. However, it is also reported as a common rice weed from Italy. Like C. esculentus, Cyperus sphacelatus Rottb. occurs in aerobic and transplanted rice systems, with examples from African and Asian countries. Its distribution range seems, however, restricted. It was reported, for example, from Malaysia and Benin. Not so frequent examples of sedges reported in rice were Cyperus aromaticus (Ridl.) Mattf. & Kük., Cyperus compressus L., Cyperus ferax Rich., Cyperus haspan L. Cyperus tenuispica Steud., and Cyperus polystachyos Rottb.

4.4. Club rushes and spike rushes (Table 5) Club rushes (Schoenoplectus and Scirpus species) and spike rushes (Eleocharis species) play a global role as rice weeds also. Fimbristylis miliacea (L.) Vahl syn Scirpus miliaceus L. syn Fimbristylis littoralis Gaudich. is frequently noted in Asian, African, and South American countries (for example, Schaedler et al., 2015). Eleocharis

Table 4 Cyperus complex reported from various rice growing regions of world.

Australia Bangladesh Benin Brazil Cambodia China Colombia ^te d'Ivoire Co Egypt Hungary India Indonesia Iran Italy Japan Korea Laos Macedonia Malaysia Nepal Nigeria Pakistan Philippines Portugal Senegal Spain Sri Lanka Thailand USA Vietnam

CYPDI

CYPES

CYPIR

CYPRO

x x x x

x x x

x

x x x x x x x x

x

x

x

x x x x x

x

x x x

x x x x

x x x x x x x x x x

CYPDI ¼ C. difformis. CYPES ¼ C. esculentus. CYPIR ¼ C. iria. CYPRO ¼ C. rotundus. CYPSE ¼ C. serotinus. CYPHP ¼ C. haspan.

x x x x x

x

CYPHP

x

x x

x

x

CYPSE

x x x x

x x x x x x x x

x

x x x

x

H. Kraehmer et al. / Crop Protection 80 (2016) 73e86

transplanted rice grown in Asian countries. Some less frequent species representing local characteristics are Eleocharis congasta D. Don, Eleocharis dulcis (Burm.f.) Trin. Ex Henschel, Eleocharis geniculata (L.) Roem. & Schult., Eleocharis tetraquetra Nees, Eleocharis yokoscensis (Franch. & Sav.) Tang & F.T. Wang, Fimbristylis dichotoma (L.) Vahl., Fimbristylis diphylla (Retz.) Vahl, Fimbristylis ferruginea Tang & F.T. Wang, Scirpus erectus Poir, Scirpus nipponicus Makino, Scirpus planiculmis Fr. Schm., Scirpus supinus L., Scirpus zeylanica Poir., and Schenoplectus pungens (Vahl) Palla.

Table 5 Club rushes and spike rushes. ELOAC Australia Bangladesh Benin Brazil Cambodia China ^ te d'Ivoire Co Hungary India Indonesia Italy Japan Korea Laos Macedonia Malaysia Philippines Portugal Spain Thailand USA Vietnam

ELOKU

FIMMI

SCPJU

x x x x x x

x

x x

x x

x

x x

SCPMA

SCPMU x

x

x

x

x x

x x

x x

4.5. Other monocot weeds

x

x

4.5.1. Grasses (Table 6) Some grasses such as Cynodon dactylon (L.) Pers., Dactyloctenium aegyptium (L.) Willd., Digitaria sanguinalis (L.) Scop, Eleusine indica (L.) Gaertn., or Paspalum distichum L. can occur as weeds of different arable crops and of perennial plantations such as sugar cane or citrus plantations. They tolerate all kinds of stresses including low oxygen contents as typical of temporary submergence. This becomes evident from the anatomical analysis of the root aerenchyma as demonstrated by Kraehmer and Baur (2013). They are no typical paddy weeds. Others, such as some Brachiaria-, Leersia-, and Leptochloa-species easily survive long-term floods. Leptochloa species have gained importance within the last decades. This is why their role as weeds in rice will be mentioned separately below.

x

x x

x

x x x

x

x x x

x

79

x

ELOAC ¼ E. acicularis. ELOKU ¼ E. kuroguwai. FIMMI ¼ F. miliacea syn F. littoralis. SCPJU ¼ S. juncoides syn Schoenoplectus scirpoides (Schrad.) Browning. SCPMA ¼ S. maritimus syn Bolboschoenus maritimus (L.) Palla. SCPMU ¼ S. mucronatus syn Schoenoplectus mucronatus (L.) Palla.

4.5.2. Broadleaved monocots (Table 7) Most monocot broadleaved weeds are typical aquatic species, for example, Alisma-, Heteranthera-, Monochoria-, and Sagittariaspecies. This is why they are usually found in flooded and paddy rice systems. Alisma- and Heteranthera-species are frequent weeds in direct-seeded, flooded rice in Europe. Monochoria- and

acicularis (L.) Roem. & Schult., Eleocharis kuroguwai Ohwi, and Scirpus juncoides Roxb. syn Schoenoplectus juncoides (Roxb.) Palla. are also rather common species. They are mainly found in

Table 6 Other monocot weeds e Grasses. CYNDA Australia Bangladesh Brazil Cambodia China Colombia ^ te d'Ivoire Co Egypt India Indonesia Italy Japan Korea Laos Macedonia Malaysia Nepal Nigeria Pakistan Philippines Spain Sri Lanka Thailand USA Vietnam

DTTAE

ELEIN

ISCRU

LERHE

LEFCH

LEFFU

PASDS

x x x

x

x

x x

x x x x

x x x

x x

x

x x

x

x

x

x x

x x x

x x

x x

x

x

x

x x

x

x

x

x

x x x

x

x x

x x

x

x

CYNDA ¼ Cynodon dactylon (L.) Pers. DTTAE ¼ Dactyloctenium aegyptium (L.) Willd. ELEIN ¼ Eleusine indica (L.) Gaertn. ISCRU ¼ Ischaemum rugosum Salisb. LERHE ¼ Leersia hexandra Sw. LEFCH ¼ Leptochloa chinensis (L.) Nees. vis syn Diplachne fusca. LEFFU ¼ Leptochloa fusca (L.) Kunth, Re PASDS ¼ Paspalum distichum L.

x x

x x

x x

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H. Kraehmer et al. / Crop Protection 80 (2016) 73e86

4.6. Dicot weeds (Table 8)

Table 7 Other monocot weeds e Broadleaf weeds. ALSPA Australia Bangladesh Brazil Cambodia China India Indonesia Iran Italy Japan Korea Laos Macedonia Malaysia Pakistan Philippines Portugal Spain Thailand Turkey USA Vietnam

HETLI

HETRE

x x

x

x

x

MOOVA

SAGMO

x x x x x x x

x

The number of dicot weeds is considerably lower than those of monocot weeds. Amaranthus species such as Amaranthus viridis L. grow preferably in irrigated crops, for example, in maize and cotton. This species is quite common for example in Africa (Rodenburg et al., 2011). Trianthema portulacastrum L. is a frequent weed in other crops than rice in India and Pakistan also (e.g., Reddy and Tyagi, 2005; Saeed et al., 2010).

SAGTR

x

x x

x x x

5. Weeds specific to rice growing areas

x x

More than 1800 plant species have been recorded in paddy fields in the last century (Kamoshita et al., 2014). The fact that we concentrate here on a bit more than 50 species is that these species have managed to dominate in very diverse environments. One might assume that regional conditions and special selection pressure have led to local weed differentiations. Mortimer (1990) tries to define some principles for the establishment of weeds in a crop, such as preadaptation, evolution, and alien immigration. The history of rice culture, however, varied from country to country. In principle, there are two extremes as far as the history of rice growing areas is concerned: countries such as China, India, and Sub-Saharan Africa where rice was cultivated for several thousand years and countries with a rice history of one to two centuries only. It is rather easy to talk about typical rice weeds in long-history countries. To classify rice weeds in Australia or the USA as “endemic”, however, sounds artificial. Some endemic wetland weeds in the USA such as Sagittaria montevidensis Cham. & Schltdl. may have found rice fields as a new habitat. They have, however, coexisted with rice for a rather short time only. The infestation of rice fields with this weed cannot be regarded as an evolutionary process nor are there clear signs of preadaptation or alien

x x x x x x

x

x x

x x

x

x x

x

x x

ALSPA ¼ Alisma plantago-aquatica L. HETLI ¼ Heteranthera limosa (Sw.) Willd. HETRE ¼ Heteranthera reniformis Ruiz & Pav. MOOVA ¼ Monochoria vaginalis (Burm. f.) C. Presl. SAGMO ¼ Sagittaria montevidensis Cham. & Schltdl. SAGTR ¼ Sagittaria trifolia L.

Sagittaria-species do not play a role as weeds in Europe. They seem to prevail in areas of transplanted rice or in California and Australia where pre-germinated seed is sown by aeroplane.

Table 8 Dicot weeds eOnly selected references are listed. ALRSE Australia Bangladesh Benin Brazil Cambodia China ^ te d'Ivoire Co Egypt India Indonesia Italy Japan Korea Laos Macedonia Malaysia Pakistan Philippines Portugal Senegal Spain Sri Lanka Thailand Vietnam

AMAVI

ECLAL

LIDPY

LUDLI

LUDOC

LUDPR

TRTPO

x x x x x x

x

x

x x

X x x

X

x x

x x

x

x

x

x

x

x

X X

x x x x x

ALRSE ¼ Alternanthera sessilis (L.) DC. AMAVI ¼ Amaranthus viridis L. ECLAL ¼ Eclipta prostrata (L.) L. LIDPY ¼ Lindernia procumbens (Krock.) Philcox syn Lindernia pyxidaria L. LUDLI ¼ Ludwigia hyssopifolia (G. Don) Exell. LUDOC ¼ Ludwigia octovalvis (Jacq.) P.H. Raven. LUDPR ¼ Ludwigia prostrata Roxb. TRTPO ¼ Trianthema portulacastrum L.

x

x x

H. Kraehmer et al. / Crop Protection 80 (2016) 73e86

immigration. One major source of weed propagules in directseeded rice is presumably uncertified and contaminated seed, for example, described by Chin and Mortimer (2002) for SouthVietnam. Many weeds described in Tables 2e8 dominated rice fields already more than 30 years ago as exemplified by tables published by Smith (1983). Rice management systems have, however, changed over time. Mahajan et al. (2014) have outlined that water management has a major impact on the infestation of weeds. Increasing water shortage and increasing labour costs drive the trend towards direct seeding on dry or wet land, low water amount consuming methods instead of transplanting rice in paddies. Many weed species growing in rainfed upland rice fields cannot survive in paddies with high water levels. This is why water was one element to control weeds in the past. A classical weed atlas is called “The world's worst weeds” (Holm et al., 1977). In this atlas, C. rotundus is listed as the world's worst weed. Unfortunately, this kind of classification appears to be problematic today. Is a weed a plant that is bad because it just reduces yields, is it bad because it is hard to control, does it impede harvest, is it toxic, does it prevent biodiversity due to its dominance? There are many reasons why a weed can be defined as bad. Which scale should we choose when trying to define weeds as worse or worst? It is rather easy to count weeds per unit area. It is, however, already difficult to quantify the term “hard to control”. In some countries, farmers might be in a position to afford expensive herbicides with a good performance against weeds, such as C. rotundus. In other parts of the world, farmers may neither have an access to such herbicides nor have the financial background to use such tools. In some countries, weeds might be classified as bad based on mechanical control tools such as hand weeding. Rice mimicking weeds such as some Echinochloa species might there be regarded as hard-to-control. Shifts in weed spectra over years have been noticed by several scientists. Some weed problems seem to be

81

rather specific to direct-seeded and upland rice. Gupta and O'Toole (1986) described a few weeds such as some Amaranthus species, Cynodon dactylon L., or E. indica (L.) Gaertn., which were already regarded as typical in the last century. Many of these upland weeds and weeds in aerobic rice are actually no typical rice weeds. We find them in other irrigated crops also as described above. One example for weeds which seem to gain importance due to shifts towards direct dry- or wet-seeded rice are different Leptochloa species, such as Leptochloa chinensis (L.) Nees. and Leptochloa fascicularis (Lam.) A. Gray (Table 7). Other species seem to be typical of paddy rice with high water levels, such as C. serotinus, E. kuroguwai, or Butomus umbellatus. Weedy rice is common to all rice growing systems. This is also true for Echinochloa species. 6. Conclusions on generalists 6.1. Which weeds are the most common and hard to control ones? Figs. 2 and 3 visualize the distribution of the most common rice weeds of the world. Weeds are ranked by frequency. Unfortunately, systematic frequency assessments based on phytosociological studies do not exists to the same extent as for many other arable crops than rice. The most frequent weeds globally are Echinochloa species and weedy rice species. They are followed by Cyperus species and other representatives of the Cyperaceae family. These weeds occur in all kinds of rice cropping systems as they tolerate varying levels of hypoxia (oxygen deficiency). Leptochloa species have become serious problems in rice at the end of the 20th century. In parts of some Asian countries, such as Malaysia or Vietnam, L. chinensis has become one of the most dominant grass species in rice (Karim et al., 2004). It was observed for the first time in Italy in the beginning of the 21st century (Benvenuti et al., 2004). So far, however, it has not become a problem in Italy.

Fig. 2. The most common rice weeds of the world.

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H. Kraehmer et al. / Crop Protection 80 (2016) 73e86

Fig. 3. The second most common rice weeds of the world.

6.2. How long does it take for generalists to establish? Rice grown in rainforests by slash and burning technology has no typical generalist weeds in the beginning (De Rouw et al. 2014). It would be interesting to see how long it takes for these areas to be infested with cosmopolitan species if continually used for rice growing. A quite recent example for the adaptation of weeds to crops are results of research projects in Alaska which could demonstrate how an endemic flora can change and how new nonnative weed species can settle on newly cleared agricultural fields due to man's activity in a rather short time span (Conn et al., 2010). Within 23 years of agricultural practice, seven new weeds could establish on Alaskan fields that were not present before. Weedcontaminated crop seed was mentioned as one major source of weed infestation. Animals feeding on weed seeds such as birds migrating over long distances can be another source. The example of Australian rice weeds as described in the introduction to this review proves that weeds can establish easily on fields within less than a century. 6.3. Which selection principles lead to regional weed infestation differences? Different cultivation methods are one reason for regional differences and shifts in weed spectra as mentioned above. Zero-till and dry seeding seem to favour weed species, such as Digitaria ciliaris (Retz.) Koeler, E. indica, Eclipta prostrata (L.) L., and Ludwigia ~ a, 2012). octovalvis (Jacq.) P.H. Raven (Chauhan and Open The plasticity and ability of some weed species to adapt to various habitats is another reason. It is quite obvious that a few weeds in rice are not well defined taxonomically, examples are Echinochloa species and weedy rice biotypes, hybrids, and species. This leads to the occurrence of global weed complexes with closely

related biotypes, varieties, or sub-species. Herbicide resistance is a common phenomenon in species with a high degree of plasticity. Resistance of rice weeds to herbicides with different modes of action (MoAs) have been reported for several decades. In the past, propanil and ACCase (acetyl-CoA carboxylase) resistance in grasses were major and global issues (Valverde, 2007). Today, publications on weeds resistant to ALS(acetolactate synthase) also called AHAS-inhibitors (acetohydroxy acid synthase) are the most frequent ones. Busi et al. (2006) compared biotypes of C. difformis and Schoenoplectus mucronatus from California, Italy, and Spain to describe cross-resistance phenomena to a number of ALS-herbicides. Several articles have been published in the recent years referring to ALS-resitance in Clearfield systems (e.g., Burgos et al. 2008; Busconi et al., 2012; Scarabel et al. 2012 or Kaloumenos et al., 2013a). The impact of such traits and resistance issues in weedy rice are discussed by Ziska et al. (2015) in detail. Many factors contribute to the fast adaptation of resistant weeds such as the above mentioned continuous rice cultivation without crop rotations or the use of uncertified seed in dry-seeded rice. The number of articles on herbicide-resistant weeds is, however, overwhelming and cannot be referred to in detail here. As a matter of fact, herbicide resistance is a primary phenomenon in the most frequent rice weeds. It has not led to principal weed shifts favouring weeds which were less frequent in the past. Some species seem to be limited as far as their adaptability to different conditions is concerned. They are mentioned as regional specialties in Table 9. Some of them can be found in rice fields which are several thousand miles apart, for example, Leptochloa fusca subsp. uninervia (J. Presl) N. Snow in Brazil, Spain, and China. L. fascicularis is a common species in the USA and Spain. A few representatives of the monocot broadleaf weed genus Heteranthera such as Heteranthera reniformis are presumably of

H. Kraehmer et al. / Crop Protection 80 (2016) 73e86

83

Table 9 Weed species diversity e specific weeds. Specific weeds

Countries/Regions

Aeschynomene indica L. Alisma canaliculatum A. Br. Et Bouche Amaranthus spinosus L., Ludwigia octovalvis Jacq.) P.H. Raven Brachiaria plantaginea (Link) Hitchc. syn Urochloa plantaginea (Link) R.D. Webster Brachiaria platyphylla (Munro ex C. Wright) Nash, Sesbania exaltata (Raf.) Cory Butomus umbellatus L. Chromolaena odorata (L.) R.M. King & H. Rob., Striga hermonthica (Delile) Benth, Striga asiatica (L.) Kuntze Cyperus aromaticus (Ridl.) Mattf. & Kuek. Cyperus compressus Jacq. Cyperus haspan L. Cyperus polystachyos Rottb. Cyperus sphacelatus Rottb. Cyperus tenuispica Steud. Digitaria sanguinalis (L.) Scop Eleocharis dulcis (Burm.f.) Trin. Ex Henschel Eleocharis geniculata (L.) Roem. & Schult. Eleocharis kuroguwai, Scirpus nipponicus Fimbristylis dichotoma (L.) Vahl. Fimbristylis diphylla (Retz.) Vahl Fimbristylis ferruginea (L.) Vahl Leptochloa fascicularis (Lam.) Gray syn Leptochloa fusca ssp. fascicularis Leptochloa uninervia (J. Presl) Hitchc. & A. Chase syn Leptochloa fusca subsp. uninervia Oldenlandia corymbosa L. Scirpus zeylanica Poir.

Japan, Korea Japan Philippines Brazil USA, Vietnam Mediterranean area Sub-Saharan Africa Malaysia India Cambodia, Malaysia Vietnam Benin, Malaysia India, Pakistan India, USA China, Vietnam Bangladesh, Vietnam Japan, Korea Nepal, Thailand Bangladesh, Vietnam Benin Spain, USA Brazil, China, Spain Sub-Saharan Africa, India Philippines

American origin (http://www.hear.org/pier/species/heteranthera_ reniformis.htm, visited February 9, 2015). Today, they are rather typical of European rice fields. They can, however, also cause problems in some Brazilian and US American rice fields. Sagittaria species are also well adapted to aquatic and wetland conditions. There are, however, preferences of single species. Sagittaria montevidensis Cham. & Schltdl. is reported as typical of Australian, US American, and Brazilian rice fields whereas Sagittaria trifolia L. seems to be more frequent in Asian countries such as Japan, Korea, and Vietnam. In Europe, Sagittaria species are no major problem weeds in rice. This is also true for Monochoria species. Several aquatic dicots which found their way into rice fields are sometimes referred to as complexes as there are often several species involved. One example is the “Ludwigia-complex”. In Brazil, this consists primarily of Ludwigia elegans (Cambess.) H. Hara, Ludwigia longifolia (DC.) H. Hara, and L. octovalvis (Andres et al., 2013b). In Asia, we find L. octovalis and other Ludwigia species (Table 8). Lindernia procumbens (Krock.) Philcox syn Lindernia pyxidaria L. is a species of Eurasian origin which is a rather rare wetland pioneer in northern Europe. It is, however, more frequent in warmer climates of the northern hemisphere. Climate creates preferred niches. However, the background for regional preferences in aquatic species is in many cases not clear yet.

7. Conclusions This review makes clear that a few dominant rice weed species such as Echinochloa species, weedy rice, and several Cyperus species have spread all over the world whereas some other species seem to be specific to some areas such as A. viridis, B. umbellatus, E. kuroguwai, Monochoria vaginalis, or T. portulacastrum. The most dominant weeds of today were already problem weeds 30 years ago. Many crop management factors contribute to weed problems in rice such as continuous rice cultivation without crop rotation, uncertified seed in systems in which rice is not transplanted, weed infestation along water ways, tillage, protection of weeds by fungicides or insecticides and many others. One major factor is, however, the impact of water. The need to save water globally has led to

rice growing systems with less water consumption such as the cultivation of aerobic rice. The weed associations in these cropping systems differ from paddy systems; the overall weed diversity and the overall weed pressure is higher. With this trend, new generalists will presumably be selected which occur in crops other than rice also. This fact will lead to an increase in herbicide use not only in rice. On the other hand, systems without dams and levees will allow more frequent crop rotations and the application of more weed control tools than in continuously flooded fields. The global distribution of dominant rice weeds makes clear that none of the existing management systems with reduced water levels will contribute to their suppression. Chemical industries searching for herbicides try to focus rather on a reduced number of key-weeds instead of trying to find solutions for everything. Our results provide a guideline. We would like to recommend here the concentration on Echinochloa species, weedy rice, Cyperus- and Leptochloa species in the first instance. References Adigun, J., Lagoke, T., Adekpe, I., 2005. Efficacy of selected herbicides for weed control in rain-fed upland rice in the Nigerian Northern Guidea Savanna. Agric. Tropica Subtropica 38, 99e104. Ahmed, S., Chauhan, B.S., 2014. Performance of different herbicides in dry-seeded rice in Bangladesh. Sci. World J. 2014, 14. Article ID 729418. http://dx.doi.org/ 10.1155/2014/729418. open access. Ahmed, S., Salim, M., Chauhan, B.S., 2014. Effect of weed management and seed rate on crop growth under direct dry seeded rice systems in Bangladesh. PLoS One 9, e101919. Altop, E.K., Mennan, H., 2011. Genetic and morphologic diversity of Echinochloa crus-galli populations from different origins. Phytoparasitica 39, 93e102. Ampong-Nyarko, K., De Datta, S.K., 1991. A Handbook for Weed Control in Rice. IRRI, Manila, Philippines. Andres, A., Concenco, G., Theisen, G., Galon, L., Tesio, F., 2012. Management of red rice (Oryza sativa) and barnyardgrass (Echinochloa crus-galli) grown with sorghum with reduced rate of atrazine and mechanical methods. Exp. Agric. 48, 587e596. Andres, A., Convenço, G., Theisen, G., Vidotto, F., Ferrero, A., 2013a. Selectivity and weed control efficacy of pre- and post-emergence applications of clomazone in Southern Brazil. Crop Prot. 53, 103e108. Andres, A., Theisen, G., Convenço, G., Galon, L., 2013b. Weed resistance to herbicides in rice fields in Southern Brazil. In: Price, A.J., Kelton, J.A. (Eds.), HerbicidesCurrent Research and Case Studies in Use, 3-25. InTech, Janeza Trdine 9, 51000 Rijeka, Croatia. http://dx.doi.org/10.5772/56743.

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H. Kraehmer et al. / Crop Protection 80 (2016) 73e86

Anwar, M., Juraimi, A., Mohamed, M., et al., 2013. Integration of agronomic practices with herbicides for sustainable weed management in aerobic rice. Sci. World J. 12. Article ID 916408. http://dx.doi.org/10.1155/2013/916408. open access. Anwar, P., Juraimi, A.S., Man, A., Puteh, A., Selamat, A., Begum, M., 2010. Weed suppressive ability of rice (Oryza sativa L.) germplasm under aerobic soil conditions. Aust. J. Crop Sci. 4, 706e717. Aoki, D., Yamaguchi, H., 2009. Oryza sh4 gene homologue represents homoeologous genomic copies in polyploidy Echinochloa. Weed Biol. Manag. 9, 225e233. Baki, B.B., Chin, D.V., Mortimer, M., 2000. Wild and Weedy Rice in Rice Ecosystems in Asia e a Review. In: Limited Proceedings, 2. IRRI, Manila, Philippines. Baloch, M.S., Hassan, G., Morimoto, T., 2005. Weeding techniques in transplanted and direct wet-seeded rice in Pakistan. Weed Biol. Manag. 5, 190e196. Barkworth, M.E., Capels, K.M., Long, S., Piep, M.B., 2003. Flora of North America: North of Mexico. In: Magnoliophyta: Commelinidae (In Part): Poaceae, Part 2, 25. Oxford. Begum, M., Juraimi, A.S., Azmi, M., Rajan, A., Syed Omar, S.R., 2005. Weed vegetation of direct seeded ricefields in Muda Rice Granary of peninsular Malaysia. Pak. J. Biol. Sci. 8, 537e541. Benvenuti, S., Dinelli, G., Bonetti, A., 2004. Germination ecology of Leptochloa chinensis: a new weed in the Italian rice agro-environment. Weed Res. 44, 87e96. Bhurer, K., Yadav, D., Ladha, J., Thapa, R., Pandey, K., 2013. Effect of integrated weed management practices on performance of dry direct seeded rice (Oryza sativa L.). Agron. J. Nepal 3, 53e63. Biswas, M., Parveen, S., Shimozawa, H., Nakagoshi, N., 2005. Effects of Azolla species on weed emergence in a rice paddy ecosystem. Weed Biol. Manag. 5, 176e183. Braverman, M.P., 1995. Weed control in rice (Oryza sativa) with quinclorac and bensulfuron coating of granular herbicides and fertilizer. Weed Technol. 494e498. Buehring, N.W., Baldwin, F.L., Talbert, R.E., Scherder, E.F., Lovelace, M.L., 2001. Graminicides in programs for broad spectrum weed control in rice. In: Norman, R.J., Meullenet, J.F. (Eds.), B.R. Wells e Rice Research Studies, Arkansas Agricultural Experiment Station, University of Arkansas Research Serious 485, pp. 58e61. Burgos, N.R., Norsworthy, J.K., Robert, R.C., Smith, K.L., 2008. Red rice (Oryza sativa) status after 5 years imidaziloninone-resistant rice technology in Arkansas. Weed Technol. 22, 200e208. Busi, R., Vidotto, F., Fischer, A.J., Oscuna, M.D., De Prado, R., Ferrero, A., 2006. Patterns of resistance to ALS herbicides in smallflower umbrella sedge (Cyperus difformis) and ricefield bulrush (Schoenoplectus mucronatus). Weed Technol. 20, 1004e1014. Busconi, M., Rossi, D., Lorenzoni, C., Baldi, G., Fogher, C., 2012. Spread of herbicideresistant weedy rice (red rice, Oryza sativa L.) after 5 years of Clearfield rice cultivation in Italy. Plant Biol. 14, 751e759. Calha, I.M., Osuna, M.D., Serra, C., Moreira, I., De Prado, R., Rocha, F., 2007. Mechanism of resistance to bensulfuron-methyl in Alisma plantago-aquatica biotypes from Portuguese rice paddy fields. Weed Res. 47, 231e240. Cao, Q.J., Li, B., Song, Z.P., Cai, X.X., Lu, B.R., 2007. Impact of weedy rice populations on the growth and yield of direct-seeded and transplanted rice. Weed Biol. Manag. 7, 97e104. Carretero, J.L., 1986. Ricefield flora and vegetation in provinces of the Valencia and Tarragona (Spain). Collect. Bot. Barc. 17, 113e124. Casimero, M.C., Martin, E.C., Donayre, D.K.M., Beltran, J.C., Talon, E.M., Argumento, J., Arroyo, C.A., Marsh, S.P., Llewellyn, R.S., 2006. Participatory adaptation of an integrated weed management strategy for wet direct-seeded rice in the Philippines. In: Preston, C., Watts, J.H., Crossman, N.D. (Eds.), 15th Australian Weeds Conference e Papers and Proceedings. Gilingham Printers, Adelaide, Australia, pp. 320e323, 24e28 September 2006. Caton, B.P., Foin, T.C., Hill, J.E., 1999. A plant growth model for integrated weed management in direct seeded rice I. Development and sensitivity analyses of monoculture growth. Field Crops Res. 62, 129e143. Chadhar, A., Nadeem, M., Tanveer, A., Yaseen, M., 2014. Weed management boosts yield in fine rice under system of rice intensification. Planta Daninha 32, 291e299. Chapagain, T., Riseman, A., Yamaji, E., 2011. Assessment of system of rice intensification (SRI) and conventional practices under organic and inorganic management in Japan. Rice Sci. 18, 311e320. Chauhan, B.S., Mahajan, G., Virender, S., Timsina, J., Jat, M.L., 2012. Productivity and sustainability of the rice-wheat cropping system in the Indo-Gangetic plains of the Indian subcontinent: problems, opportunities, and strategies. Adv. Agron. 117, 315e369. Chauhan, B.S., 2013a. Effect of tillage systems, seeding rates, and herbicides on weed growth and grain yield in dry-seeded rice systems in the Philippines. Crop Prot. 54, 244e250. Chauhan, B.S., 2013b. Effect of shade on growth and yield of weedy rice (Oryza sativa L.) biotypes and a rice (Oryza sativa L.) cultivar from Asia. J. Crop Improv. 27, 272e280. Chauhan, B.S., 2013c. Strategies to manage weedy rice in Asia. Crop Prot. 48, 51e56. Chauhan, B.S., Johnson, D.E., 2011a. Row spacing and weed control timing affect yield of aerobic rice. Field Crops Res. 121, 226e231. Chauhan, B.S., Abugho, S.B., 2013. Weed management in mechanized-sown, zerotill dry-seeded rice. Weed Technol. 27, 28e33. Chauhan, B.S., Johnson, D.E., 2011b. Competitive interactions between weedy rice and cultivated rice as a function of added nitrogen and the level of competition. Weed Biol. Manag. 11, 202e209. Chauhan, B.S., Ngoc, S.T.T., Duong, D., Ngoc, P.L., 2014. Effect of pretilachlor on

weedy rice and other weeds in wet-seeded rice cultivation in South Vietnam. Plant Prod. Sci. 17, 315e320. ~ a, J., 2012. Effect of tillage systems and herbicides on weed Chauhan, B.S., Open emergence, weed growth, and grain yield in dry-seeded rice systems. Field Crops Res. 137, 56e69. Chin, D.V., 2001. Biology and management of barnyardgrass, red sprangletop and weedy rice. Weed Biol. Manag. 1, 37e41. Chin, D.V., Mortimer, M., 2002. Weed management in direct-seeded rice in South Vietnam. In: Pandey, S., Mortimer, M., Wade, L., Tuong, T.P., Lopez, K., Hardy, B. (Eds.), Direct-seeding: Research Strategies and Opportunities. International Rice ~ os, Philippines, 349-356, 349e356. Research Institute, Los Ban Chhokar, R.S., Sharma, R.K., Gathala, M.K., Pundir, A.K., 2014. Effects of crop establishment techniques on weeds and rice yield. Crop Prot. 64, 7e12. Conn, J.S., Werdin-Pfisterer, N.R., Beattie, K.L., 2010. Development of the Alaska agricultural weed flora 1981-2004: a case for prevention. Weed Res. 51, 63e70. Dai, L., Dai, W., Song, X., Lu, B., Qiang, S., 2014. A comparative study of competitiveness between different genotypes of weedy rice (Oryza sativa) and cultivated rice. Pest Manag. Sci. 70, 113e122. Danquah, E.Y., Johnson, D.E., Riches, C., Arnold, G.M., Karp, A., 2002. Genetic diversity in Echinochloa spp. collected from different geographic origins and ^te d'Ivoire. Weed Res. 42, 394e405. within rice fields in Co De Rouw, A., Casagrande, M., Phaynaxay, K., Soulileuth, B., Saito, K., 2014. Soil seedbanks in slash-and-burn rice fields of northern Laos. Weed Res. 54, 26e37. De Sousa, A.M.B., Santos, R.R.S., Moraes, F.H.R., Gehring, C., 2012. Exploring the potential for sustainable weed control with integrated ricefish culture for ~o Lowlands of Amazonia. smallholder irrigated rice agriculture in the Maranha Renew. Agric. Food Syst. 27, 107e114. De Wet, J.M.J., Prasada, R., Mengesha, M.H., Brink, D.E., 1983. Domestication of Sawa millet (Echinochloa colona). Econ. Bot. 37, 283e291. Dilipkumar, M., Adzemi, M.A., Chuah, T.S., 2012. Effects of soil types on phytotoxic activity of pretilachlor in combination with sunflower leaf extracts on barnyardgrass (Echinochloa crus-galli). Weed Sci. 60, 126e132. Ekeleme, F., Kamara, A.Y., Oikeh, S.O., et al., 2009. Response of upland rice cultivars to weed competition in the savannas of West Africa. Crop Prot. 28, 90e96. Ferrero, A., Tinarelli, A., 2008. Rice cultivation in the E.U. ecological conditions and agronomical practices. In: Capri, E., Karpouzas, D.G. (Eds.), Pesticide Risk Assessment in Rice Paddies: Theory and Practice. Elsevier, Amsterdam, The Netherlands, pp. 1e24. Florez, J.A., Fischer, A.J., Ramirez, H., Duque, M.C., 1999. Predicting rice yield losses caused by multispecies weed compositions. Agron. J. 91, 87e92. Fofana, B., Rauber, R., 2000. Weed suppression ability of upland rice under lowinput conditions in West Africa. Weed Res. 40, 271e280. Fogliatto, S., Vidotto, F., Ferrero, A., 2011. Germination of weedy rice in response to field conditions during winter. Weed Technol. 25, 252e261. ndez-Valiente, Videira R., Peixoto, F., 2011. Galhano, V., Gomes-Laranjo, J., Ferna Impact of herbicides on non-target organisms in sustainable irrigated rice production systems: state of knowledge and future prospects. In: Kortekamp, A. (Ed.), Herbicides and Environment, pp. 45e72. InTech, Janeza Trdine 9, 51000 Rijeka, Croatia. Gealy, D.R., Anders, M., Watkins, B., Duke, S., 2014. Crop performance and weed suppression by weed-suppressive rice cultivars in furrow-and flood-irrigated systems under reduced herbicide inputs. Weed Sci. 62, 303e320. Goulart, I.C., Borba, T.C., Menezes, V.G., Merotto Jr., A., 2014. Distribution of weedy red rice (Oryza sativa) resistant to imidazolinone herbicides and its relationship to rice cultivars and wild Oryza species. Weed Sci. 62, 280e293. Gressel, J., 2005. Crop Ferality and Volunteerism. CRC Press, Boca Raton, FL, USA. Grist, D.H., 1965. Rice. Longmans, London, UK. Gupta, P.C., O'Toole, J.C., 1986. Upland rice: a Global Perspective. IRRI, Manila, Philippines. Hakim, M.A., Juraimi, A.S., Ismail, M.R., Hanafi, M.M., Selamat, A., 2013. A survey of weed diversity in coastal rice fields of Sebarang Perak in peninsular Malaysia. J. Anim. Plant Sci. 23, 534e542. Hirosue, T., Yamasue, Y., Yabuno, T., 2000. Shattering habit and dormancy of spikelets in a cultivated form of Echinochloa oryzicola recently found in China. Weed Res. 40, 449e456. Holm, L.G., Plucknettt, D.L., Pancho, J.V., Herberger, J.P., 1977. The World's Worst Weeds. The University Press of Hawaii, Honolulu, USA. Hoshikawa, K., 1989. The Growing Rice Plant. Nobunkyo, Tokyo. Huaqi, W., Bouman, B.A.M., Zhao, D., Changgui, W., Moya, P.F., 2002. Aerobic rice in northern China: opportunities and challenges. In: Bouman, B.A.M., Hengsdijk, H., Hardy, B., Bindraban, P.S., Tuong, T.P., Ladha, J.K. (Eds.), Waterwise Rice Production, Proceedings of the International Workshop on Water~ os (Philippines). International Wise Rice Production, 8e11 April 2002, Los Ban Rice Research Institute, Manila, Philippines, pp. 143e154. Hussain, S., Ramzan, M., Akhter, M., Aslam, M., 2008. Weed management in direct seeded rice. J. Anim. Pl. Sci. 18, 2e3. Hussain, Z., Man, A., Othman, A.S., 2011. Association of commercial rice varieties with weedy rice accessions (Oryza sativa complex) in Pulau Pinang's rice granary area. Trop. Life Sci. Res. 22, 1e11. Hwang, I.T., Kim, H.R., Choi, J.S., et al., 2006. Synthesis and herbicidal activity of new 3-(3-bromothiophen-2-yl)-5-(2, 6-difluorobenzyl) oxymethyl-5-methyl-4, 5dihydroisoxazole as a paddy field herbicide. Weed Biol. Manag. 6, 102e106. Ibrahim, T.S.I., 1989. Integrated weed control in rice. In: Rice farming Systems e New Directions. Proceedings of an International Symposium 31 January - 3 February 1987, Rice Research and Training Center Sakha, Egypt. International

H. Kraehmer et al. / Crop Protection 80 (2016) 73e86 Rice Research Institute, Manila, Philippines, pp. 161e166. Imeokparia, P.O., 1994. Weed control in flooded rice with various herbicide combinations in the Southern Guinea Savanna zone of Nigeria. Int. J. Pest Manag. 40, 31e39. Iwakami, S., Uchino, A., Watanabe, H., Yamasue, Y., Inamura, T., 2012. Isolation and expression of genes for acetolactate synthase and acetyl-CoA carboxylase in Echinochloa phyllopogon, a polyploidy weed species. Pest Manag. Sci. 68, 1098e1106. Jacob, D., Syriac, E.K., 2005. Performance of transplanted scented rice (Oryza sativa L.) under different spacing and weed management regimes in southern Kerala. J. Trop. Agric. 43, 71e73. Jena, K.K., Hardy, B., 2012. Advances in Temperate Rice Research. IRRI, Dapo, Metro Manila, Philippines. Johnson, D.E., Kent, R.J., 2002. The impact of cropping on weed species composition in rice after fallow across a hydrological gradient in west Africa. Weed Res. 42, 89e99. Johnson, D., Wopereis, M., Mbodj, D., Diallo, S., Powers, S., Haefele, S., 2004. Timing of weed management and yield losses due to weeds in irrigated rice in the Sahel. Field Crops Res. 85, 31e42. Juraimi, A.S., Yusof, M., Najib, M., et al., 2009. Critical period of weed competition in direct seeded rice under saturated and flooded conditions. Pertanika J. Trop. Agric. Sci. 32, 305e316. Kabir, M.H., Bari, M.N., Haque, M.M., Ahmed, G.J.U., Islam, J.M.S., 2008. Effect of water management and weed control treatments on the performance of transplanted Aman rice. Bangladesh J. Agric. Res. 33, 399e408. Kaloumenos, N.S., Capote, N., Aguado, A., Eleftherohorinos, I.G., 2013a. Red rice (Oryza sativa) cross-resistance to imidazolinone herbicides used in resistant rice cultivars grown in northern Greece. Pestici. Biochem. Physiol. 105, 177e183. Kaloumenos, S.N., Chatzilazaridou, S.L., Mylona, P.V., Polidoros, A.N., Eleftherohorinos, I.G., 2013b. Target-site mutation associated with crossresistance to ALS-inhibiting herbicides in late watergrass (Echinochloa oryzicola Vasing.). Pest Manag. Sci. 69, 865e873. Kamoshita, A., Araki, Y., Nguyen, Y.T.B., 2014. Weed biodiversity and rice production during the irrigation rehabilitation process in Cambodia. Agric. Ecosyst. Environ. 194, 1e6. Karim, R.S., Man, A.B., Sahid, I.B., 2004. Weed problems and their management in rice fields of Malaysia: an overview. Weed Biol. Manag. 4, 177e186. Kent, R., Johnson, D., 2001. Influence of flood depth and duration on growth of lowland rice weeds, Cote d’Ivoire. Crop Prot. 20, 691e694. Kent, R., Johnson, D., Becker, M., 2001. The influences of cropping system on weed ^ te d’Ivoire, West Africa. Agric. Ecosyst. Environ. 87, communities of rice in Co 299e307. Khaliq, A., Matloob, A., Ihsan, M.Z., Abbas, R.N., Aslam, Z., Rasul, F., 2013. Supplementing herbicides with manual weeding improves weed control efficiency, growth and yield of direct seeded rice. Int. J. Agric. Biol. 15, 191e199. Khanh, T.D., Xuan, T.D., Chin, D.V., CHung, I.M., Abdelghany, E.A., Tawata, S., 2006. Current status of biological control of paddy weeds in Vietnam. Weed Biol. Manag. 6, 1e9. Kim, S.-C., Ha, W.-G., 2005. Direct seeding and weed management in Korea. In: Toriyama, K., Heong, K.L., Hardy, B. (Eds.), Rice Is Life: Scientific Perspectives for the 21st Century, pp. 181e184. Koger, C.H., Walker, T.W., Krutz, L.J., 2006. Response of three rice (Oryza sativa) cultivars to pendimethalin application, planting depth, and rainfall. Crop Prot. 25, 684e689. Kraehmer, H., Baur, P., 2013. Weed Anatomy. Wiley-Blackwell, Chichester, UK. Krupnik, T.J., Shennan, C., Settle, W.H., Demont, M., Ndiaye, A.B., Rodenburg, J., 2012. Improving irrigated rice production in the Senegal River Valley through experiential learning and innovation. Agric. Syst. 109, 101e112. Kumalasari, R.N., 2014. Diversity of Rice Weeds Vegetation and its Potential as Local Forage Resource in Java, Indonesia (Dissertation, Georg-August-University €ttingen, Germany). Go Kuroda, Y., Appa Rao, S., BounphanousaY, C., Kongphanh, K., Tanaka, K., Sato, Y.I., 2006. Diversity of wild and weedy rice in Laos. In: Schiller, J.M., Chanphengxay, M.B., Linquist, B., Appa Rao, A. (Eds.), Rice in Laos. International Rice Research Institute, Manila, Philippines, pp. 215e234. Lal, B., Gautam, P., Raja, R., et al., 2014. Weed community composition after 43 years of long-term fertilization in tropical riceerice system. Agric. Ecosyst. Environ. 197, 301e308. Li, S.-S., Wei, S.-H., Zuo, R.-L., Wei, J.-G., Qiang, S., 2012. Changes in the weed seed bank over 9 consecutive years of riceeduck farming. Crop Prot. 37, 42e50. Lundy, M., Hill, J., van Kessel, C., et al., 2014. Site-specific, real-time temperatures improve the accuracy of weed emergence predictions in direct-seeded rice systems. Agric. Syst. 123, 12e21. Mahajan, G., Chauhan, B.S., Kumar, V., 2014. Integrated weed management in rice. In: Chauhan, B.S., Mahajan, G. (Eds.), Recent Advances in Weed Management. Springer ScienceþBusiness Media, New York, USA, pp. 125e153. Mahajan, G., Chauhan, B.S., Timsina, J., 2012. Opportunities for weed control in dry seeded rice in North-Western Indo-Gangetic Plains. In: Alvarez-Fernandez, R. (Ed.), Herbicides e Environmental Impact Studies and Management Approaches. InTech, Rijeka, Croatia, pp. 199e208. Mandal, M., Duary, B., De, G., 2013. Effect of crop establishment and weed management practices on weed growth and productivity of Basmati rice. Indian J. Weed Sci. 45, 166e170. Mann, R.A., Ahmad, S., Hassan, G., Baloch, M.S., 2007. Weed management in direct seeded rice crop. Pak. J. Weed Sci. Res. 13, 219e226.

85

McIntyre, S., Barrett, S.C.H., 1985. A comparison of weed communities of rice in Australia and California. Proc. Ecol. Soc. Aust. 14, 237e250. Men, B.X., Tinh, T.K., Preston, T., Ogle, R.B., Lindberg, J.E., 1999. Use of Local Ducklings to Control Insect Pests and Weeds in the Growing Rice Field. In: Livestock Research for Rural Development, 11. http://lrrd.cipav.org.co/lrrd11/2/men112. htm (accessed January 24, 2015). Mennan, H., Kaya-Altop, E., 2012. Molecular techniques for discrimination of late watergrass (Echinochloa oryzicola) and early watergrass (Echinochloa oryzoides) species in Turkish rice production. Weed Sci. 60, 525e530. Michael, P.W., 1983. Taxonomy and distribution of Echinochloa species with special reference to their occurrence as weeds of rice. In: Proceedings of the Confer~ os, ence on Weed Control in Rice, 31 August-4September 1981, Los Ban Philippines. International Rice Research Institute, Manila, Philippines, pp. 291e306. Midya, A., Bhattacharjee, K., Ghose, S., Banik, P., 2005. Deferred seeding of blackgram (Phaseolus mungo L.) in rice (Oryza sativa L.) field on yield advantages and smothering of weeds. J. Agron. Crop Sci. 191, 195e201. Mohtisham, A., Ahmad, R., Ahmad, Z., Aslam, M.R., 2013. Effect of different mulches techniques on weed infestation in aerobic rice (Oryza sativa L.). Am. Eurasian J. Agric. Environ. Sci. 13, 153e157. Moon, B., Kim, J., Cho, S., Park, J., Song, J., Kim, D., 2014. Modelling the effects of herbicide dose and weed density on rice-weed competition. Weed Res. 54, 484e491. Moody, K., 1989. Weeds Reported in Rice in South and Southeast Asia. International Rice Research Institute, Manila, Philippines. Mortimer, A.M., 1990. The biology of weeds. In: Holly, K., Hance, R. (Eds.), The Weed Control Handbook: Principles. Blackwell Scientific Publications, UK, pp. 1e42. Motlagh, M.R.S., Sharifi, P., 2011. Evaluation of the reaction of Sagittaria trifolia (arrowhead) and some rice cultivars to Fusarium equiseti. Aust. J. Crop Sci. 5, 453e457. Moukoumbi, Y., Sie, M., Vodouhe, R., Bonou, W., Toulou, B., Ahanchede, A., 2011. Screening of rice varieties for their weed competitiveness. Afr. J. Agric. Res. 6, 5446e5456. Mudge, C.R., Webster, E.P., Zhang, W., Leon, C.T., 2005. Rice (Oryza sativa) response to clomazone plus bensulfuron and halosulfuron. Weed Technol. 19, 879e884. Mukherjee, D., Singh, R., 2005. Effect of micro-herbicides on weed dynamics, yield and economics of transplanted rice (Oryza sativa). Indian J. Agron. 50, 292e295. Norsworthy, J.K., Bond, J., Scott, R.C., 2013. Weed management practices and needs in Arkansas and Mississippi rice. Weed Technol. 27, 623e630. Ntanos, D., Koutroubas, S., 2000. Competition of barnyardgrass with rice varieties. J. Agron. Crop Sci. 184, 241e246. Osca, J.M., 2013. Expansion of Leptochloa fusca ssp. uninerva and Leptochloa fusca ssp. fascicularis in rice fields in Valencia, eastern Spain. Weed Res. 53, 479e488. Pacanoski, Z., Glatkova, G., 2009. The use of herbicides for weed control in direct wet-seeded rice (Oryza sativa L.) in rice production regions in the Republic of Macedonia. Plant Prot. Sci. 45, 113e118. Phuong, L., Denich, M., Vlek, P., Balasubramanian, V., 2005. Suppressing weeds in direct-seeded lowland rice: effects of methods and rates of seeding. J. Agron. Crop Sci. 191, 185e194. zy, A., et al., 2014. The impact of management on weeds Pinke, G., Csiky, J., Mesterha and aquatic plant communities in Hungarian rice crops. Weed Res. 54, 388e397. Pittelkow, C.M., Fischer, A.J., Moechnig, M.J., Hill, J.E., Koffler, K.B., Mutters, R.G., Greer, C.A., Cho, Y.S., Van Kessel, C., Linquist, B.A., 2012. Agronomic productivity and nitrogen requirements of alternative tillage and crop establishment systems for improved weed control in direct-seeded rice. Field Crops Res. 130, 128e137. Pons, T.L., 1982. Factors affecting weed seed germination and seedling growth in lowland rice in Indonesia. Weed Res. 22, 155e161. Prathepha, P., 2009. Seed morphological traits and genotypic diversity of weedy rice (Oryza sativa f. spontanea) populations found in the Thai Hom Mali rice fields of north-eastern Thailand. Weed Biol. Manag. 9, 1e9. Prathepha, P., 2011. Microsatellite analysis of weedy rice (Oryza sativa f. spontanea) from Thailand and Lao PDR. Aust. J. Crop Sci. 5, 49e54. Pratley, J.E., Flower, R., Heylin, E., Sivapalan, S., 2004. Integrated Weed Management Strategies for the Rice Weeds Cyperus difformis and Alisma plantago-aquatica. Rural Industries Research and Development Corporation, Kingston, Australia. RIRDC Publication No 04/008. Raj, S.K., Jose, N., Mathew, R., Leenakumary, S., 2013. Chemical management of nongrassy weeds in direct-seeded rice. Indian J. Weed Sci. 45, 159e162. Rashid, M.H., Alam, M.M., Rao, A., Ladha, J., 2012. Comparative efficacy of pretilachlor and hand weeding in managing weeds and improving the productivity and net income of wet-seeded rice in Bangladesh. Field Crops Res. 128, 17e26. Rao, A.N., Johnson, D.E., Sivaprasad, B., Ladha, J.K., Mortimer, A.M., 2007. Weed management in direct-seeded rice. Adv. Agron. 93, 153e254. Ratnasekera, D., Perera, U.I., He, Z., et al., 2014. High level of variation among Sri Lankan weedy rice populations, as estimated by morphological characterization. Weed Biol. Manag. 14, 68e75. Reddy, D.A., Tyagi, S.K., 2005. Integrated weed management in maize e groundnut sequential cropping system e a review. Agric. Rev. 26, 235e248. Roder, W., 2006. Weed ecology in the rice environments of Laos. In: Schiller, J.M., Chanphengxay, M.B., Linquist, B., Appa Rao, A. (Eds.), Rice in Laos. International Rice Research Institute, Manila, Philippines, pp. 309e323. Rodenburg, J., Meinke, H., Johnson, D.E., 2011. Challenges for weed management in African rice systems in a changing climate. J. Agric. Sci. 149, 427e435.

86

H. Kraehmer et al. / Crop Protection 80 (2016) 73e86

Rodenburg, J., Demont, M., Sow, A., Dieng, I., 2014. Bird, weed and interaction effects on yield of irrigated lowland rice. Crop Prot. 66, 46e52. Roham, R., Pirdashti, H., Yaghubi, M., Nematzadeh, G., 2014. Spatial distribution of nutsedge (Cyperus spp. L.) seed bank in rice growth cycle using geostatistics. Crop Prot. 55, 133e141. Saeed, M., Marwat, K.B., Hassan, G., Khan, A., Khan, I.A., 2010. Interference of horse purslane (Trianthema portulacastrum L.) with maize (Zea mays L.) at different densities. Pak. J. Bot. 42, 173e179. Sakagami, J.-I., Joho, Y., Chiharu, S., 2013. Complete submergence escape with shoot elongation ability by underwater photosynthesis in African rice, Oryza glaberrima Steud. Field Crops Res. 152, 17e26. Saito, K., Azoma, K., Rodenburg, J., 2010. Plant characteristics associated with weed competitiveness of rice under upland and lowland conditions in West Africa. Field Crops Res. 116, 308e317. Saito, K., Futakuchi, K., 2014. Improving estimation of weed suppressive ability of upland rice varieties using substitute weeds. Field Crops Res. 162, 1e5. Sanusan, S., Polthanee, A., Audebert, A., Seripong, S., Mouret, J.-C., 2010. Suppressing weeds in direct-seeded lowland rainfed rice: effect of cutting dates and timing of fertilizer application. Crop Prot. 29, 927e935. Scarabel, L., Cenghialta, C., Manuello, D., Sattin, M., 2012. Monitoring and management of imidazolinone-resistant red rice (Oryza sativa L., var. sylvatica) in Clearfield® Italian paddy rice. Agronomy 2, 371e383. Schaedler, C.E., Burgos, N.R., Noldin, J.A., Alcober, E.A., Salas, R.A., Agostinetto, D., 2015. Competitive ability of ALS-inhibitor herbicide-resistant Fimbristylis miliacea. Weed Res. 55, 482e492. Semon, M., Nielsen, R., Jones, M.P., Mccouch, S.R., 2005. The population structure of African cultivated rice Oryza glaberrima (Steud.): evidence for elevated levels of LD caused by admixture with O.sativa and ecological adaptation. Genetics 169, 1639e1647. Shen, X., Gao, X., Eneji, A.E., Chen, Y., 2013. Chemical control of weedy rice in precise hill-direct-seeded rice in South China. Weed Biol. Manag. 13, 39e43. Shibayama, H., 2001. Weeds and weed management in rice production in Japan. Weed Biol. Manag. 1, 53e60. Silva, M., Durigan, J., 2006. Periods of weed interference in the upland rice: I-Variety IAC 202. Planta Daninha 24, 685e694. Singh, K., Kumar, V., Saharawat, Y.S., Gathala, M., Ladha, J.K., Chauhan, B.S., 2013. Weedy rice: an emerging threat for direct-seeded rice production systems in India. J. Rice Res. 1 http://dx.doi.org/10.4172/jrr.1000106, 1e6, 106. Singh, M., Bhullar, M.S., Chauhan, B.S., 2014. The critical period for weed control in dry-seeded rice. Crop Prot. 66, 80e85. Smith, R.J., 1983. Weeds of major economic importance in rice and yield losses due to weed competition. In: Proceedings of the Conference on Weed Control in ~ os, Philippines. International Rice Rice, 31 August-4September 1981, Los Ban Research Institute, Manila, Philippines, pp. 291e306. Somado, E.A., Guei, R.G., Keya, S.O., 2008. NERICA e the New Rice for Africa e a Compendium. WARDA, Cotonou, Benin. Sparacino, A., Bocchi, S., Ferro, R., Riva, N., Tano, F., 1996. The use of herbicides for weed control in flooded rice in North Italy. Hydrobiologia 340, 265e269. Sparacino, A.C., Santin, C., Ditto, D., Tano, F., 2007. Morphological characteristics of the most spread Echinochloa spp. in Italian rice-fields. In: Proceedings of the Fourth Temperate Rice Conference, Novara, Italy, 25-28 June, 2007, pp. 1e2. Strand, L., 2013. Integrated Pest Management for Rice, third ed. University of California Statewide Integrated Pest Management Project, Division of Agriculture and Natural Resources. Publication Number: 3280. Street, J.E., Teresiak, H., Boykin, D.L., Allen, R.L., 1995. Interaction between timings and doses of quinclorac in rice. Weed Res. 35, 75e79. Sudianto, E., Ben-Kah, S., Teng-Xiang, N., Saldain, N.E., Scott, R.C., Burgos, N.R., 2013a. Clearfield® rice: its development, success, and key challenges on a global perspective. Crop Prot. 49, 40e51. Sudianto, E., Ben-Kah, S., Teng-Xiang, N., Saldain, N.E., Scott, R.C., Burgos, N.R., 2013b. Corrigendum to “Clearfield® rice: its development, success, and key challenges on a global perspective”. Crop Prot. 55, 142e144.

Tan, N.T., Son, N.H., Trung, H.M., Auld, B.A., Hetherington, S.D., 2000. Weed flora of water rice in the Red River Delta, Vietnam. Int. J. Pest Manag. 46, 285e287. Tomita, S., Nawata, E., Kono, Y., Nagata, Y., Noichana, C., Sributta, A., Inamura, T., 2003. Differences in weed vegetation in response to cultivating methods and water conditions in rainfed paddy fields in north-east Thailand. Weed Biol. Manag. 3, 117e127. Toure, A., Rodenburg, J., Marnotte, P., Dieng, I., Huat, J., 2014. Identifying the problem weeds of rice-based systems along the inland-valley catena in the southern Guinea Savanna, Africa. Weed Biol. Manag. 14, 121e132. Towa, J.J., Guo, X., Zhen, B., 2013. Effects of water management and mulching on weed control and rice grain yield under water saving irrigation model. Journal of Food. Agric. Environ. 11, 538e544. Tuong, T., Pablico, P., Yamauchi, M., Confesor, R., Moody, K., 2000. Increasing water productivity and weed suppression of wet seeded rice: effect of water management and rice genotypes. Exp. Agric. 36, 71e89. Turki, Z., Sheded, M., 2002. Some observations on the weed flora of rice fields in the Nile Delta, Egypt. Feddes Repert. 113, 394e403. Vasconcelos, T., Tavares, M., Gaspar, N., 1999. Aquatic plants in the rice fields of the Tagus Valley, Portugal. Hydrobiologia 415, 59e65. Valverde, B.E., 2007. Status and management of grass-weed resistance in Latin America. Weed Technol. 21, 310e323. Vaughan, D.A., Sanchez, P.L., Ushiki, J., Kaga, A., Tomooka, N., 2005. Asian rice and weedy rice- evolutionary perspectives. In: Gressel, J. (Ed.), Crop Ferality and Volunteerism. CRC Press, Taylor and Francis Group, Boca Raton, FL, USA, pp. 257e277. Viggiani, P., Tabacchi, M., Angelini, R., 2003. Vegetazione spontanea di risaie e canali. Bayer CropScience Milano: Edizioni L'Informatore agrario. Wan, K., Tao, Y., Li, R., Pan, J., Tang, L., Chen, F., 2012. Influences of long-term different types of fertilization on weed community biodiversity in rice paddy fields. Weed Biol. Manag. 12, 12e21. Watanabe, H., 2011. Development of lowland weed management and weed succession in Japan. Weed Biol. Manag. 11, 175e189. Webster, E., 2014. Weed management. In: Saichuk, J. (Ed.), Lousiana Rice Production Handbook, pp. 54e81. LSU AgCenter Pub 2321. Weerakoon, W., Mutunayake, M., Bandara, C., Rao, A., Bhandari, D., Ladha, J., 2011. Direct-seeded rice culture in Sri Lanka: lessons from farmers. Field Crops Res. 121, 53e63. Xuan, T.D., Tsuzuki, E., Uematsu, H., Terao, H., 2001. Weed control with alfalfa pellets in transplanting rice. Weed Biol. Manag. 1, 231e235. Yamada, S., Kusumoto, Y., Tokuoka, Y., Yamamoto, S., 2011. Landform type and land improvement intensity affect floristic composition in rice paddy fields from central Japan. Weed Res. 52, 51e62. Yamaguchi, H., Utano, A., Yasuda, K., Yano, A., Soejima, A., 2005. A molecular phylogeny of wild and cultivated Echinochloa in East Asia inferred from non-coding region sequences of trnT-L-F. Weed Biol. Manag. 5, 210e218. Yamasue, Y., 2001. Strategy of Echinochloa oryzicola Vasing. for survival in flooded rice. Weed Biol. Manag. 1, 28e36. Yasuda, K., Yano, A., Nakayama, Y., Yamaguchi, H., 2002. Molecular identification of Echinochloa oryzicola and E. crus-galli using a polymerase chain reactionrestriction fragment length polymorphism technique. Weed Biol. Manag. 2, 11e17. Yu, G., Olsen, K.M., Schaal, B.A., 2011. Molecular evolution of the endosperm starch synthesis pathway genes in rice (Oryza sativa L.) and its wild ancestor, O. rufipogon L. Mol. Biol. Evol. 28, 659e671. Zhang, Z., Dai, W., Song, X., Qiang, S., 2014. A model of the relationship between weedy rice seed-bank dynamics and rice-crop infestation and damage in Jiangshu Province, China. Pest Manag. Sci. 70, 716e724. Ziska, L.H., Gealy, D.R., Burgos, N., Caicedo, A.L., Gressel, J., Lawton-Rauh, A.L., Avila, L.A., Theisen, G., Norsworthy, J., Ferrero, A., Vidotto, F., Johnson, D.E., Ferreira, F.G., Marchesan, E., Menezes, V., Cohn, M.A., Linscombe, S., Carmona, L., Tang, R., Merotto, A., 2015. Weedy (red) rice: an emerging constraint to global rice production. Adv. Agron. 181e228 (Elsevier).