Sweetpotato:Sweetpotato:Sweetpotato: MajorMajorMajor PPPests,ests,ests, Diseases,Diseases, andand NutritionalNutritional DisordersDisordersDisorders T. Ames, N.E.J.M. Smit, A.R. Braun, J.N. O’Sullivan, and L.G. Skoglund ISBN 92-9060-187-6 Sweetpotato: Major Pests, Diseases, and Nutritional Disorders T. Ames, N.E.J.M. Smit, A.R. Braun, J.N. O’Sullivan, and L.G. Skoglund International Potato Center (CIP) C O N T E N T S The International Potato Center (CIP) is a scientific, nonprofit institution dedicated to the increased and more sustainable use of potato, Page sweetpotato, and other roots and tubers in the Foreword vii developing world, and to the improved management of agricultural resources in the Acknowledgments viii Andes and other mountain areas. CIP is part of the global agricultural research network known as the Consultative Group on Introduction 1 International Agricultural Research (CGIAR). CGIAR Insect Pests of Sweetpotato and Their Management 3 International Potato Center Apartado 1558 Storage Root Feeders 4 Lima 12, Peru Sweetpotato Weevils (Cylas spp.) 4 West Indian Sweetpotato Weevil (Euscepes ISBN 92-9060-187-6 postfasciatus)10 Press run: 1000 Rough Sweetpotato Weevil (Blosyrus sp.) 12 Printed in Lima, Peru August, 1997 Clearwing Moth (Synanthedon spp.) 14 Peloropus Weevil (Peloropus batatae)14 Cover: Photo of chlorotic spots with and without purple margins induced White Grubs 15 by SPFMV (taken by S. Fuentes). Stemborers and Feeders 16 T. Ames, N.E.J.M. Smit, A.R. Braun, J.N. O’Sullivan, and L.G. Skoglund. Clearwing Moth (Synanthedon spp.) 16 1996. Sweetpotato: Major Pests, Diseases, and Nutritional Disorders. International Potato Center (CIP). Lima, Peru. 152 p. Sweetpotato Stemborer (Omphisia anastomasalis)18 Striped Sweetpotato Weevil (Alcidodes dentipes and 1. Sweetpotato – Insect pests. 2. Sweetpotato – Diseases. A. erroneus)22 3. Sweetpotato – Nutritional disorders. 4. Sweetpotato – Integrated manage- Sweetpotato Weevils (Cylas spp.) 24 ment. I. International Potato Center. Minor Stemborers and Feeders 25 Peloropus Weevil (Peloropus batatae)25 Sweetpotato Bug (Physomerus grossipes)26 Long-Horned Beetle 26 Foliage Feeders 28 Sweetpotato Butterfly (Acraea acerata)28 Tortoiseshell Beetles (Aspidomorpha spp. and others) 30 Sweetpotato Hornworm (Agrius convolvuli)34 Armyworms (Spodoptera eridania, S. exigua, S. litura) 36 iii Page Page Leaf Folders (Brachmia convolvuli, Herpetogramma Sweetpotato Sunken Vein Virus (SPSVV) hipponalis, and others) 40 (Whitefly-transmitted closterovirus) 68 Strobiderus Beetle (Strobiderus aequatorialis)43 Sweetpotato Virus Disease (SPVD) 69 Rough Weevil (Blosyrus sp.) 43 Sweetpotato Mild Mottle Virus (SPMMV) Sweetpotato Weevils (Cylas spp.) 43 (Whitefly-transmitted potyvirus) 70 Minor Leaf Feeders 44 Other Viral Diseases 71 Grasshoppers and Locusts (Zonocerous variegatus, the variegated grasshopper and Attractomorpha Bacterial Diseases 72 psitticina, the slant-faced grasshopper, Bacterial Stem and Root Rot (Erwinia chrysanthemi)72 and others) 44 Bacterial Wilt (Pseudomonas solanacearum)74 Soil Rot (Streptomyces ipomoea)76 Virus Transmitters 46 Aphids (Aphis gossypii and others) 46 Foliar and Stem Diseases Caused Whiteflies (Bemisia tabaci)48by Fungi 78 Leaf and Stem Scab (Elsinoe batatas, Sphaceloma Mites 50 batatas)78 Erinose caused by Eriophyid mites, Aceria sp. 50 Alternariosis, Anthracnose, Blight (Alternaria bataticola) 80 Eriophyes gastrotrichus 50 Phomopsis Leaf Spot (Phyllosticta Leaf Spot) (Phomopsis ipomoea-batatas Natural Enemies 52 (Phyllosticta batatas)) 82 Earwigs 53 Minor Leaf Spot Fungi 84 Spiders 53 Chlorotic Leaf Distortion (Fusarium lateritium)86 Pheidole and Other Predacious Ants 54 Fusarium Wilt (Fusarium oxysporum f. sp. batatas)88 Beetles 56 Violet Root Rot (Helicobasidium mompa)90 Flies and Parasitic Wasps 58 Sclerotial Blight and Circular Spot (Sclerotium rolfsii) 92 Viruses 61 Black Rot (Ceratocystis fimbriata)94 Fungal Pathogens (Metarrhizium anisopliae and Beauveria bassiana)62Storage Root and Postharvest Diseases 96 Diseases and Pathogens of Sweet- Foot Rot (Plenodomus destruens)96 potato and Their Management 65 Java Black Rot (Lasiodiplodia theobromae (Diplodia gossypina)) 98 Viral Diseases 66 Charcoal Rot (Macrophomina phaseolina) 100 Sweetpotato Feathery Mottle Virus (SPFMV) Soft Rot (Rhizopus stolonifer, Mucor sp.) 102 (Aphid-transmitted potyvirus) 66 iv v Foreword Page This field guide presents information on common pests, Diseases Caused by Nematodes 104 diseases and nutritional disorders of sweetpotato. It is Root-Knot Nematode (Meloidogyne spp.) 104 intended primarily as a tool for correct identification of Brown Ring (Ditylenchus destructor, D. dipsaci) 106 these problems and ailments, as an essential first step Reniform Nematode (Rotylenchulus reniformis) 108 Lesion Nematode (Pratylenchus spp.) 110 in their control. Disorders of Unknown Origin 112 The principal entries in the guide are accompanied Fasciation 112 by photographs or illustrations, and pinpoint where specific problems occur. Additional information is provided on Nutritional Disorders and Their symptoms and recommended control practices, with Management 115 emphasis on integrated crop management. Causes of Nutritional Disorders 116 We believe that researchers, extension agents, stu- Diagnosing Nutritional Disorders 117 Correcting Nutritional Disorders 118 dents and farmers alike will find this guide useful, as Nutrient Requirements of Sweetpotato 120 it can assist them in controlling pests and diseases while Nitrogen Deficiency 122 safeguarding the natural environment needed for sus- Phosphorus Deficiency 124 tainable agriculture. Potassium Deficiency 130 Magnesium Deficiency 132 Wanda Collins Boron Deficiency 134 Deputy Director General for Research Iron Deficiency 136 International Potato Center Acid Soils and Aluminum Toxicity 138 Salinity 140 Literature Consulted 142 About the Authors 146 Photo Credits 147 Index 148 vi vii Acknowledgments Introduction The information on nutritional disorders of sweetpotato The purpose of this field guide is to aid researchers presented in this field guide was derived from a research and extensionists throughout the world in the identification project of the Australian Centre for International Agricultural of common pests, diseases, and nutritional disorders of Research (ACIAR). The author of the section on nutritional sweetpotato (Ipomoea batatas). This guide is based on disorders, J.N. O’Sullivan, is a member of the project based the authors’ experiences with the crop in various regions at the University of Queensland, Australia. of the world since 1990. We would like to thank virologist Richard W. Gibson In contrast to most other major staple food crops, of the Natural Resources Institute for contributing to the sweetpotato is able to produce a comparatively high yield section on virus diseases. under relatively adverse conditions; however, a number of pests, diseases, and nutritional disorders affect the crop. Among the pest and disease constraints, sweetpotato weevils (Cylas spp.) and virus diseases probably contribute the most to yield losses, although leaf-feeding insects, such as the sweetpotato butterfly (Acraea acerata), can cause significant losses during outbreaks. Nutritional disorders can cause slight to complete yield loss, and are the main factor limiting most unfertilized crops. They may also reduce tolerance of pests and diseases. The basis for successful management of sweetpotato pests, diseases, and nutritional disorders is integrated crop management. This implies prevention of insect infestation and infection by pathogens through the use of adequate cultural practices, and the conservation of natural enemies. Adequate cultural practices include the selection of healthy planting material from well-adapted varieties, rotation, good field sanitation, and maintenance of soil fertility. Conser- vation of natural enemies involves avoidance of pesticide use, enhancement of natural enemy action through favorable cultivation practices, and the introduction of natural enemies if necessary. viii 1 Insect Pests of Sweetpotato and Their Management Integrated crop management for sweetpotato is cov- Many insect species attack sweetpotato and the im- ered comprehensively in the Farmer Field School Guide portance of different species varies between agroecological for Sweetpotato Integrated Crop Management. This pub- zones. Within a zone, the importance of a species depends lication can be obtained from the CIP Regional Office for on the season; many insect pests are a problem mainly East and Southeast Asia and the Pacific or from CIP in dry periods. headquarters in Lima.1 Nutritional disorders are covered comprehensively in the publication Nutritional Disorders In this guide, we divide pest species into three groups of Sweet Potato,2 available from the Australian Centre for according to whether the damage is caused to leaves, International Agricultural Research. stems, or roots. Defoliation reduces yield depending on the severity of infestation and the growth stage of the The photographs in this publication were assembled sweetpotato crop in which it occurs. In some areas, from the collections of the authors and their colleagues, sweetpotato is grown for its foliage and leaf feeders can and are acknowledged as such. be a problem. In addition to feeding, certain insects, such as aphids and whiteflies, transmit viruses. Extensive stem damage can result in wilting or even in death of the plant. Damage to the vascular system caused by