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Conclusions and Recommendations Mpigi, Masaka and Rakai, is recorded as having increased significantly during the second half of the 1990s (Legg, 1995; Otim-Nape et al., 1997; Legg and Ogwal, 1998). This is now thought to have resulted from a synergistic interaction with an unusually severe form of CMD, which spread through Uganda during this period (Colvin et al., 1999) and continues to spread in the East and Central African region (Legg, 1999). The interaction has occurred in all agroecologies in Uganda but it remains to be seen if the same will occur in the drier agro-ecologies to the south, in Tanzania. In Madagascar, there was no clear pattern of variation in abundance (Figure 3), although abundance in the southern central areas was lower than elsewhere. Variation in abundance of sweetpotato whiteflies was much greater than for cassava whiteflies (Table 1). Very high populations were recorded around the shores of Lake Victoria, whilst whiteflies were not recorded at all from many locations in Madagascar. It is likely that seasonal effects can partly explain this degree of variation, since sweetpotato is grown for a much shorter period (typically 4-6 months) than cassava (typically 10-24 months). Thus, although cassava crops may be available throughout the year, in drier areas, sweetpotato cultivation outside the main growing season is confined to very small areas used for the maintenance of planting material. Associated with this, there is evidence showing that B. tabaci on sweetpotato colonize a wide range of crop plants and weed species, in contrast to B. tabaci on cassava, which appear to be largely restricted to cassava (Burban et al., 1992; Legg et al., 1994). Whitefly-transmitted viruses in cassava Stem samples of CMD-diseased cassava were sent from all nine principal participating countries to the John Innes Centre (JIC) for diagnostics and characterization. Chapter 1.11 (this volume) reports the results of this work. Until 1996, it was considered that two cassava mosaic begomoviruses were occurring in Africa, with largely disjunct distributions (Swanson and Harrison, 1994). African cassava mosaic virus (ACMV) was reported to occur in much of West, Central and southern Africa, and East African cassava mosaic virus (EACMV) was said to be restricted to coastal East Africa, Madagascar, Malawi and Zimbabwe. More recent diagnostic surveys have shown that EACMV is not restricted to East Africa (Offei et al., 1999; Ogbe et al., 1999), that the distributions of EACMV and ACMV overlap (Ogbe et al., 1996; 1997) and that mixed virus infections occur (Harrison et al., 1997). Results from the TWF-IPM Project (Chapter 1.11, this volume) have extended our understanding further by establishing the first record of EACMV from Benin in West Africa; identifying a novel begomovirus from cassava in Zimbabwe, which appears to be closely related to South African cassava mosaic virus (Rey and Thompson, 1998); and highlighting the occurrence of virus mixtures in East Africa. Dual infections are a relatively uncommon occurrence (< 10%) and it is significant that all these were recorded from the part of East Africa affected by the pandemic of unusually severe CMD (Otim-Nape et al., 1997; Legg 1999; Chapter 1.1, this volume). Although virus diagnoses have been carried out on only a limited number of samples, a relationship is apparent between the viruses affecting cassava plants and the disease caused. In West Africa, diversity seems to be limited and symptoms of disease are generally mild to moderate (Table 1). In East and southern Africa, by contrast, 103
104 Whiteflies and Whitefly-borne Viruses in the Tropics Table 1. Summary of data on the incidence of cassava mosaic disease (CMD), sweetpotato virus disease (SPVD) and abundance of Bemisia tabaci, from Sub-Project 4 diagnostic surveys. Country Survey area Fields a CMD Wfinf c CMD Cassava SPVD SP (%) b (miu) sev. d WF e (%) f WF g Uganda North 20 (20) 77 48.0 3.0 1.2 5.0 1.40 East 20 (20) 68 46.0 3.1 1.8 12.0 5.40 South/Central 20 (20) 79 53.0 2.8 3.8 15.0 12.40 West 20 (20) 48 55.0 2.8 9.2 10.0 3.00 Kenya Coastal Province 17 (15) 56 36.0 2.3 2.9 0.5 0.50 Western Province 15 (18) 85 64.0 2.9 0.3 6.0 2.30 Nyanza Province 18 (17) 11 2.3 2.2 0.5 7.0 4.90 Madagascar Central plateau 35 (11) 31 7.8 2.6 7.1 3.0 0.01 Humid coast 22 (15) 71 11.0 3.5 4.3 2.0 0 Dry coast 12 (7) 46 11.0 3.2 5.9 18.0 0.10 Semi-humid coast 42 (6) 41 11.0 3.3 2.6 0 0 Tanzania Lake zone plateau 20 (20) 21 1.7 2.6 0.7 11.0 40.10 Semi-humid coast 20 (20) 12 7.1 2.7 1.2 13.0 2.80 Humid coast 20 (20) 39 21.0 3.0 5.8 6.0 3.10 Malawi Central lakeshore 20 62 55.0 2.8 1.5 - - Northern lakeshore 9 52 34.0 2.7 1.0 - - Central plateau 12 11 3.7 3.0 1.3 - - Ghana Coastal savannah 10 76 44.0 2.2 11.8 - - Rainforest 25 69 23.0 2.2 1.5 - - Transition forest 25 74 54.0 2.5 1.0 - - Guinea savannah 20 68 44.0 2.4 0.3 - - Benin Transition forest 28 26 3.4 2.1 4.2 - - Wet savannah 19 43 0.5 2.1 0.7 - - Dry savannah 13 49 3.4 2.1 3.4 - - Nigeria Rainforest 25 83 3.9 2.4 3.1 - - Transition forest 25 32 2.7 2.1 2.6 - - Wet savannah 20 56 0 2.4 1.0 - - Dry savannah 10 45 2.4 2.2 0.3 - - Cameroon South-west 26 54 21.0 2.2 4.1 - - North-west 16 55 21.0 2.4 2.4 - - Centre-south 28 73 5.6 2.3 3.1 - - a. Fields: Figures in parentheses indicate number of sweetpotato fields sampled. b. CMD %: Total incidence of CMD, calculated as the average percentage of plants showing symptoms of virus disease from 30 plant samples recorded in each dataset (i.e., one field). c. Wfinf (miu): Incidence of plants infected with CMD whitefly in the current season, transformed to allow for multiple infection units (Gregory, P. H. 1948. The multiple infection transformation. Ann. Appl. Biol. 35: 412-417). d. CMD sev.: Severity of CMD symptoms, based on an arbitrary 1-5 scale, where 1 indicates low and 5 indicates high severity of symptoms. e. Cassava WF: Mean whitefly abundance for cassava recorded as the average number of adult whiteflies counted on the five uppermost leaves of 30 plant samples recorded in each field. f. SPVD %: Total incidence of SPVD, calculated as the average percentage of plants showing symptoms of virus disease from 30 plant samples recorded in each field. g. SP WF: Mean whitefly abundance for sweetpotato recorded as the average number of adult whiteflies counted in ten 1-minute counts made at random in the sampled field.
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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
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Uganda environment, host plant heal
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Uganda local varieties. Assessments
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Page 70 and 71: Kenya Recent epidemiological studie
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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
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Page 82 and 83: Tanzania Legg, J. P.; Raya, M. 1998
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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
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Page 104 and 105: Factors Associated with Damage CHAP
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Page 116 and 117: Conclusions and Recommendations Mal
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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
Page 164 and 165: Tanzania Nono-Womdim, R.; Swai, I.
Page 166 and 167: 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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