1 Ag84Ah SWEETPOTATO CULTURE AND DISEASES Agriculture Handbook No. 388 Í 5. r> ' f/5 -w --; r í73 en Agricultural Research Service UNITED STATES DEPARTMENT OF AGRICULTURE Some of the information given in this handbook is similar to that form- erly contained in U.S. Department of Agriculture Farmers' Bulletin 2020, "Commercial Growing and Harvesting of Sweetpotatoes," and in Farmers' Bulletin 1059, "Sweetpotato Diseases." Both of these reports are now out of print. Mention of a trademark name or a proprietary product does not con- stitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable. PRECAUTION Pesticides used improperly can be injurious If a pesticide is spilled on your skin or clothing, to man, animals, and plants. Follow the direc- remove clothing immediately and wash skin tions and heed all precautions on the labels. thoroughly. Store pesticides in original containers under Do not clean spray equipment or dump excess lock and key—out of the reach of children and spray material near ponds, streams, or wells. animals—and away from food and feed. Because it is difficult to remove all traces of herbicides from equipment, do not use the same Apply pesticides so that they do not endanger equipment for insecticides or fungicides that humans, livestock, crops, beneficial insects, fish, you use for herbicides. and wildlife. Do not apply pesticides when there is danger of drift, when honey bees or other Dispose of empty pesticide containers pollinating insects are visiting plants, or in promptly. Have them buried at a sanitary land- ways that may contaminate water or leave il- fill dump, or crush and bury them in a level, legal residues. isolated place. Avoid prolonged inhalation of pesticide sprays or dusts; wear protective clothing and NOTE: Some States have restrictions on the equipment if specified on the container. use of certain pesticides. Check your State and local regulations. Also, because registrations of If your hands become contaminated with a pesticides are under constant review by the pesticide, do not eat or drink until you have U.S. Department of Agriculture, consult your washed. In case a pesticide is swallowed or gets county agricultural agent or State extension in the eyes, follow the first aid treatment given specialist to be sure the intended use is still on the label, and get prompt medical attention. registered. ¿/Mpééáoüá4s^Jéé^ POU.OW THC LABBI. ' U.S. »trAITMINT or ACIICttlTUM SWEETPOTATO CULTURE AND DISEASES Agriculture Handbook No. 388 Agricultural Research Service UNITED STATES DEPARTMENT OF AGRICULTURE Washington, D.C. Issued June 1971 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 — Price $1.25 CONTENTS Part I: CULTURE Page Page Introduction 1 Amounts of seed stock required 26 Importance 2 Field planting 28 Uses 3 Methods of transplanting 28 Botany 5 Preplanting fungicidal treatment of Varieties 7 plants 29 Varietal types 7 Size of plants 30 Varietal improvement 8 Time of planting 30 Properties and characteristics of impor- Plant spacings 30 tant varieties 9 Weed control and cultivation 32 Growth requirements of sweetpotatoes _ 13 Weed control by cultural methods 32 Climatic adaptation 13 Chemical weed control 33 Soils for sweetpotato culture 13 Water requirements and irrigation 34 Crop rotation 14 Harvesting the crop 35 Land preparation 15 Methods and equipment 35 Ridge height 15 When to harvest 38 Fertilizers 16 Handling and grading in the field 41 Composition and rates of application 16 Selecting and storing seed stock 42 Nutrient deficiency symptoms 17 Curing and storing 42 Fertilizer placement 17 Purposes and requirements 42 Types and sources of planting materials 18 Storage house operation 44 Use of clean seed stock 19 Preparing sweetpotatoes for the fresh Foundation, registered, and certified market 46 seed 20 Washing 47 Producing plants 21 Sorting and grading 47 Location of plant beds 21 Treating to prevent decay 47 Types of plant beds 21 Waxing 47 Preparation of seed stock for bedding 24 Packaging 47 Bedding procedures and bed care 25 Shipping 48 Part II: DISEASES Agents causing sweetpotato diseases 49 Septoria leaf spot 60 Fungi 49 White rust 61 Nematodes 49 Nematodes and their control 61 Viruses 49 Storage rots and their control 64 General procedures for controlling sweet- Soft rot 64 potato diseases 49 Black rot 65 Field diseases 49 Surface rot 66 Storage diseases 49 Java black rot 66 Field diseases and their control 50 Dry rot 68 Stem rot 50 Virus diseases and their control 68 Black rot 53 Internal cork 68 Foot rot 55 Chlorotic leafspot 69 Scurf 56 Yellow dwarf 69 Root rot 57 Feathery mottle 70 Mottle necrosis 58 Russet crack 70 Soil rot 59 Literature cited 71 Phyllosticta leaf blight 60 Appendix 72 SWEETPOTATO CULTURE AND DISEASES By CLARENCE E. STEINBAUER, research horticulturist, retired, and LEATON J. KUSHMAN, research plant physiologist, Plant Science Research Division Agricultural Research Service Part I: CULTURE INTRODUCTION The sweetpotato (Ipomoea batatas (L.) from 1960 through 1965 (i,5).^ Sweetpotatoes Lam.) has been used as human food for many- are of prime importance in the food supplies centuries. However, early peoples of Africa, and economies of many countries. (See Appen- Asia, Australia, and Europe apparently did not dix.) Production is especially large in the Afri- use, or know of, the sweetpotato, and there is can, Far Eastern, and Latin American regions ; no available evidence that this plant was known is moderate in the North American region ; and to the ancient Arabs, Chinese, Egyptians, is notably smaller in the European, Near East- Greeks, Hebrews, Indians, or Romans. Primi- ern, and Oceanic regions (table 1). tive peoples in tropical areas of Central and The sweetpotato was used in tropical regions South America, as well as in numerous tropi- of Central and South America long before the cal islands in the Pacific, were using this plant Spanish explorations. Columbus found the na- long before first written historical records came tives in the West Indies using it, and he is into existence. In spite of the more or less re- reported to have presented a sweetpotato to stricted areas of the world in which the sweet- Queen Isabella upon his return to Spain. Other potato was known in early times, the subsequent Spanish explorers later found the plant in Mexi- spread of the plant throughout other areas of co and in South America. It probably was not the world has been very extensive. This crop cultivated in what are now the 48 contiguous plant has been referred to under numerous States of the United States before the time of names. Some of these synonyms are listed in Columbus. It may have been introduced into the Appendix of this handbook. this country later through trading among Cen- It is not possible to accurately determine in tral and North American Indian tribes. Early just what part of the world the sweetpotato American settlers probably obtained sweetpota- originated. Some authorities believe it evolved toes during trading with the West Indians. The in tropical America; others believe it evolved crop was introduced into Virginia sometime be- somewhere in the tropical South Pacific Islands. fore 1560. The evidence appears to favor American origin, Early records give only sketchy, incomplete however, because a considerable number of descriptions of the sweetpotato. Very likely the other closely related wild plant species belong- forms referred to in those early records were ing to the same botanical genus (Ipomoea) as notably different from the sweetpotatoes grown the sweetpotato are native to the American commercially in the United States today. Selec- tropics and subtropics. Among these other spe- tion and propagation of naturally occurring cies are believed to be the progenitors of the sports or mutations over the years have resulted sweetpotato. in numerous productive forms (varieties) pos- Wherever it originated, the spread of this sessing desirable horticultural characteristics. crop plant to other climatically suitable areas Some early varieties probably arose through of the world has been very extensive. Today selection of naturally occurring hybrids among sweetpotatoes are grown in tropical, subtropi- flowering types. Since 1937, with controlled cal, and warmer temperate areas throughout breeding and selection programs, rapid progress the world. The Food and Agriculture Organiza- tion of the United Nations, in Production Year- books in 1963 and 1965 estimated the world pro- ^ Italic numbers in parentheses refer to Literature duction and yields of sweetpotatoes and yams Cited p. 71. AGRICULTURE HANDBOOK 388, U.S. DEPARTMENT OF AGRICULTURE TABLE 1.—Estimated average annual produc- dredweight was produced on 1,059,000 acres. tion and yields of sweetpotatoes and yams Since that time, acreage planted, total produc- in various regions, from 1960 through tion, per capita consumption, and relative im- 1965^ portance of sweetpotatoes among vegetable Production Yield crops have decreased. These changes have oc- Region area per acre Production curred in spite of rapid increases in population and substantial increases in yields of sweet- 1,000 acres Cwt. 1,000 cwt potatoes produced per acre (table 2). Africa 2 6,323 2 61 2 392,040 Far East 4,150 89 367,048 A number of factors have contributed to Latin America 1,131 65 74,096 changes in status of the crop. Increased urban- North America 200 81 16,214 ization of our population and mechanization of Oceania 3 49 4 67 4 3,300 our industry and agriculture have reduced the Europe 35 108 3,740 Near East 11 175 1,892 overall average physical labor requirements and the needs for high-calorie foods. As a result of ^ Calculated to acres and hundredweights from metric this and of changed dietary concepts, the per units shown in Production Yearbook 1963 (4, table 26) capita consumption of all starchy foods, includ- and Production Yearbook 1965 (5, table 27).