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Conclusions and Recommendations colonization of cassava, the very low frequency of occurrence means that they are of little significance. B. tabaci and B. afer both occurred on cassava and sweetpotato, although B. afer was relatively less frequent on sweetpotato and in Uganda was not recorded from this crop. There was an important geographical zonation in the relative abundance of the two species (Figures 1-3). Whilst B. tabaci predominated in countries in the equatorial belt (Ghana, Benin, Nigeria, Cameroon, Uganda and Kenya), the two species occurred at similar frequencies in Tanzania, to the south, and B. afer predominated in the most southerly countries, Malawi and Madagascar. The reasons for this pattern of occurrence are not clear, particularly since no single environmental factor appears to correlate consistently with the species ratio. In Malawi, however, there was a significant difference in the ratio between survey areas. In the two survey areas (1 and 2) along the shore of Lake Malawi (475-700 m altitude), similar numbers of the two species were recorded; whilst in survey area 3, the central plateau (1000-1500 m altitude), 97% of specimens identified were B. afer (Chapter 1.9, this volume). The key difference between the lakeshore and plateau environments is temperature and it seems likely that the low temperatures that occur in the mid-altitude environments of southern Africa are unfavourable for B. tabaci. This possibility is supported by published information indicating that the development period of this species is significantly increased (Gerling et al., 1986) and fecundity significantly reduced (Azab et al., 1971) at temperatures below 15 ºC. More detailed ecological studies and molecular characterization of the two species will be required to clarify these issues, particularly since the current surveys were conducted only at one time in the year and therefore may not be fully representative. It is important to highlight, however, that B. afer has never been shown to transmit viruses. The distinction between the two species therefore becomes important if errors are not to be made in describing relationships between adult whitefly populations and the spread of viruses causing cassava mosaic disease (CMD) or sweetpotato virus disease (SPVD). Geographical patterns of variation in abundance of cassava whiteflies were partly confounded with the different patterns of distribution of the two species (Figures 1-3). Although survey teams were trained to differentiate the adult stages of the two species, it was not always possible for them to do so during counting. Some patterns in distribution were apparent, however. In West Africa, where B. tabaci was the dominant species, abundance was generally greater in the more humid rainforest and transition forest ecozones. Conversely, populations were smaller in the drier northern savannah zones. This is a pattern that has been recognized before, both in the Ecologically Sustainable Cassava Plant Protection (ESCaPP) surveys of 1993-94 (IITA, 1998) and through earlier studies of CMD epidemiology in Ivory Coast (Fauquet et al., 1987; 1988). In East Africa, two centres of whitefly abundance were recognized: the northern shoreline of Lake Victoria, in Uganda, and the northern Tanzania/southern Kenya coast. As for West Africa, these are also the areas in the region where humidity is greatest. It is notable, however, that abundance of B. tabaci in the “Lake Crescent” agro-ecological zone in Uganda, comprising the southern districts of Iganga, Mukono, 99
100 Whitefly abundance 0-1 1-3 3-9 9-27 Benin 27-81 CMD incidence Not surveyed Ghana 20%-30% 30%-40% Nigeria 40%-50% 50%-60% Whiteflies and Whitefly-borne Viruses in the Tropics 60%-70% 70%-80% B. afer Cameroon B. tabaci 200 0 200 400 600 Kilometers Figure 1. Whitefly abundance, cassava mosaic disease (CMD) incidence and Bemisia tabaci/B. afer ratio for Sub-Project 4 countries in West Africa.
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About the Partners CIAT The Interna
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Centro Internacional de Agricultura
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Chapter 4 Whiteflies and Whitefly-b
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Chapter 6 Whiteflies and Whitefly-b
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Contents Page Foreword vii Introduc
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Contents Chapter SECTION THREE Whit
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Foreword This book is the product o
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Introduction Introduction The Probl
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Introduction In addition to the yie
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Introduction in pesticide use in La
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Introduction annual crops, especial
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Introduction Plant Resistance contr
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Introduction Otim-Nape, G. W.; Bua,
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SECTION ONE Whiteflies as Vectors o
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Introduction CHAPTER 1.1 Introducti
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Introduction diseases than is cassa
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Introduction Sub-project on Whitefl
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Introduction References Aritua, V.;
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Introduction Thresh, J. M.; Otim-Na
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Ghana 1997, on 80 farms. These incl
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Ghana (6.2%), Bakentenma (5%) and K
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Ghana Legg, J. P.; James, B. D. 199
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Benin Northern guinea savannah Sout
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Benin or disease problem, the main
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Nigeria CHAPTER 1.4 Nigeria Introdu
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Nigeria TMS 30572 (18.8%) and TMS 3
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Nigeria FAO (Food and Agriculture O
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Cameroon protocol, to enable valid
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Cameroon Farmers undertook various
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Cameroon Robertson, I. A. D. 1987.
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Uganda between November 1997 and Ja
Page 64 and 65: Uganda environment, host plant heal
Page 66 and 67: Uganda local varieties. Assessments
Page 68 and 69: Uganda Harrison, B. D. 1987. Proper
Page 70 and 71: Kenya Recent epidemiological studie
Page 72 and 73: Kenya respective diseases were reco
Page 74 and 75: Kenya Bock, K. R. 1983. Epidemiolog
Page 76 and 77: Tanzania CHAPTER 1.8 Tanzania Intro
Page 78 and 79: Tanzania Adult whiteflies were more
Page 80 and 81: Tanzania loss) to assess yield loss
Page 82 and 83: Tanzania Legg, J. P.; Raya, M. 1998
Page 84 and 85: Malawi Increased Biological Underst
Page 86 and 87: Malawi Physiology and Ecology in th
Page 88 and 89: Madagascar Tanzania Madagascar Moza
Page 90 and 91: Madagascar surprising, particularly
Page 92 and 93: Diversity of African Cassava Mosaic
Page 98 and 99: Sweetpotato Virus Disease in East A
Page 104 and 105: Factors Associated with Damage CHAP
Page 106 and 107: Factors Associated with Damage Mean
Page 108 and 109: Factors Associated with Damage % SP
Page 110 and 111: Factors Associated with Damage thro
Page 112 and 113: Factors Associated with Damage Gedd
Page 116 and 117: Conclusions and Recommendations Mal
Page 118 and 119: Conclusions and Recommendations Mpi
Page 120 and 121: Conclusions and Recommendations com
Page 122 and 123: Conclusions and Recommendations con
Page 124 and 125: Conclusions and Recommendations (2)
Page 126 and 127: Conclusions and Recommendations Ger
Page 128 and 129: SECTION TWO Whiteflies as Pests and
Page 130 and 131: Introduction CHAPTER 2.1 Introducti
Page 132 and 133: Introduction Czosnek, H.; Navot, N.
Page 134 and 135: Sudan cotton, leading to the introd
Page 136 and 137: Sudan Table 1. Reproductive host pl
Page 138 and 139: Sudan Historically, Sudan has been
Page 140 and 141: Sudan Only 10% of producers reporte
Page 142 and 143: Sudan Conclusions The work conducte
Page 144 and 145: Kenya CHAPTER 2.3 Kenya Introductio
Page 146 and 147: Kenya Increased Biological Understa
Page 148 and 149: Kenya Samples of 10 plants per fiel
Page 150 and 151: Kenya Table 4. Maximum incidence (%
Page 152 and 153: Kenya Seventy-nine percent of tomat
Page 154 and 155: Kenya under Phase 2 of the TWF-IPM
Page 156 and 157: Tanzania CHAPTER 2.4 Tanzania Intro
Page 158 and 159: Tanzania The reproductive host plan
Page 160 and 161: Tanzania Geographical range of whit
Page 162 and 163: Tanzania Local names given to white
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Tanzania Nono-Womdim, R.; Swai, I.
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Malawi levels of infestation by the
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Malawi Table 3. Maximum incidence (
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Malawi (40%) believe that the white
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Tomato Yellow Leaf Curl Virus in E.
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Conclusions and Recommendations CHA
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Conclusions and Recommendations (Fi
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Conclusions and Recommendations Cen
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Conclusions and Recommendations the
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SECTION THREE Whiteflies as Vectors
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Introduction especially for export.
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Mexico CHAPTER 3.2 Mexico Introduct
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Mexico Culiacán, Sinaloa, in north
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Mexico Table 2. Virus survey of tom
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Mexico results of the molecular bio
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Mexico Strengthened Research Capaci
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Mexico López, R. 1996. Experiencia
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Guatemala 1960s, and at this time t
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Guatemala Table 2. Results of white
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Guatemala Table 5. Cropping systems
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Guatemala contemplated in this prel
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El Salvador CHAPTER 3.4 El Salvador
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El Salvador During the course of th
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El Salvador markets: common bean, m
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El Salvador Current Status of White
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Honduras Copan Ocotepeque Santa Bá
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Honduras Table 3. Biotyping of whit
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Honduras References Caballero, R. 1
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Nicaragua Nueva Segovia Madriz Este
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Nicaragua Lowlands of Nicaragua. Th
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Nicaragua Region VI is a main horti
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Costa Rica CHAPTER 3.7 Costa Rica I
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Costa Rica Table 1. Characterizatio
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Costa Rica Castillo, J. 1997. Movim
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Panama Bocas del Toro Chiriquí Ver
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Panama Gámez, R. 1970. Los virus d
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Haiti Grande-Anse Sud Grande-Anse S
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Haiti collaborators in this project
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Cuba Ciudad de la Habana Pinar del
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Cuba Table 3. Comparative homologie
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Cuba project provided three keynote
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Dominican Republic CHAPTER 3.11 Dom
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Dominican Republic monoclonal antib
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Dominican Republic Strengthened Res
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Reproductive Crop Hosts of Bemisia
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Biotypes of Bemisia tabaci CHAPTER
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Biotypes of Bemisia tabaci For this
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Biotypes of Bemisia tabaci 100 99 B
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Biotypes of Bemisia tabaci biotype
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Biotypes of Bemisia tabaci Table 2.
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Biotypes of Bemisia tabaci Already
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Conclusions and Recommendations gre
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SECTION FOUR Whiteflies as Pests of
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Introduction control, due to resist
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Introduction Posada, L. 1976. Lista
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Colombia and Ecuador B biotype B. t
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Colombia and Ecuador assistants and
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Colombia and Ecuador and squash. On
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Colombia and Ecuador Table 2. Main
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Colombia and Ecuador Table 6. Patte
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Insecticide Resistance in Colombia
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Conclusions and Recommendations res
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Conclusions and Recommendations rot
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SECTION FIVE Special Topics on Pest
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Sustainable IPM through Host Plant
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Biological Control of Whiteflies by
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Progress of Cassava Mosaic Disease
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Management of the Cassava Mosaic Di
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Conclusions Conclusions The Tropica
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Conclusions whitefly pests and thus
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Conclusions developing countries, a
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Acronyms and Abbreviations Acronyms
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Acronyms and Abbreviations FIRA Fid
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Acronyms and Abbreviations PROFRIJO
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Acronyms and Abbreviations PYR pyre
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Whitefly and whitefly-borne viruses in the tropics : Building a ... - cgiar

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