Background: Sweet potato [Ipomoea batatas (L.) Lam.] plays an important role in ensuring food security and incomes for local communities. It is particularly grown in southern region of Benin, and its production over the last few years has declined due to disease and severe pest infestation. Therefore, it was imperative to carry out this study to identify the main constraints related to the recent decline in sweet production and more specifically analyzing the production and marketing constraints of sweet potato in the townships of Dangbo and Bonou. Results: The results of the survey revealed that many varieties of sweet potato were grown, mainly “Vobodouaho” (local name in Goun language), the most preferred variety by producers. Weedicides and insecticides were used to control weeds and insect pests, respectively. There was no efficient control methods against black rot, Alternaria blight, cylas spp., and caterpillar among the pathogens and insects that damaged sweet potato production in the study areas. The main constraints reducing sweet potato production in the townships of Dangbo and Bonou are: lack of adequate methods for controlling pest and diseases, lack of financial resources due to no access to credit, absence of modern equipment, scarcity and high cost of labor and absence of best methods for long-term storage. The average yield of sweet production per hectare ranged from 6.5 to 15.1 tons fresh matter/ha. The market value of sweet potato is still low at farmers’ level when compared to that of other stakeholders along the value chain. Conclusion: This study calls for the attention of public and private sectors and policy makers for more investment in sweet potato research. Avenues for further research on sweet potato have also been suggested. Keywords: Actors in sweet potato, Horticulture, Limitations, Productivity, Revenue Roots (PDRT) in collaboration with partners for devel- Background opment such as International Fund for Agricultural Benin is an essentially agricultural country where 70% Development (IFAD) and West African Bank of Devel- of the population lives in rural areas . This population opment (BOAD) . The program aims at rationalizing basically practices agriculture of subsistence. Among the sustainably production, transformation and marketing main staple food crops cultivated are tubers and roots. of tubers and roots through reinforcement of techno- In order to encourage the development of these crops logical capacities. Among tubers and roots are cassava, and improve their contribution to the food security, taro, yam, potato and sweet potato. The findings of the Benin government, through its policy of diversification present research strengthen the Ministry of Agricul- of agricultural production and fight against poverty, has ture in its program of intensify tubers and roots and initiated the Program of Development of Tubers and ultimately stimulate calls for attention for more invest- ment in sweet potato research in order to help farmers *Correspondence: firstname.lastname@example.org; email@example.com increase their productivity and revenues. Sweet potato Department of Crop Production, Faculty of Agricultural Science, University of Abomey-Calavi, Abomey-Calavi, Benin can adapt to different ecological conditions and requires Full list of author information is available at the end of the article © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Ezin et al. Agric & Food Secur (2018) 7:15 Page 2 of 12 few inputs for its cultivation . It is an important food Methods and vegetable crop in most developing countries where Study site and choice of study area it was ranked fifth economically after rice, wheat, maize The municipalities of Dangbo and Bonou are located in and cassava . Sweet potato is grown mainly for the the department of Ouémé. Dangbo Township is bounded fresh market. The fresh market sweet potato tubers are in the north by Adjohoun Township, in the south by sold in the surrounding markets around the study areas, Aguégués Township, in the east by Akpro-Missérété which need to be improved upon for high price and sub- Township and in the west by Sô-Ava Township. As for sequent high income. The sweet potato value chain of Bonou, it is bounded in the north by the Ouinhi Town- different innovative platform approaches is required to ship, in the south by Adjohoun, in the east by Sakété and facilitate work in the farms and postharvest operations Adja-Ouèrè Townships and in the west by Zê and Zog- and at the same time improve the quality of sweet potato bodomé Township. Dangbo and Bonou cover a total land products including improve nutritional value and food area of 149 and 250 km , respectively. and nutritional security; and strengthen the capacity of With the poor distribution of rainfall observed nowa- all stakeholders in order to alleviate poverty along the days, the seasons underwent noticeable change (PDC2 value chain. Bonou, 2013–2017). In the last 20 years, the total average From nutritional point of view, all the parts of sweet annual rainfall is 1237 mm (ASECNA, 2012) with a tem- potato are rich in food fibers, the leaves and the stems perature that varies between 25 and 30 °C. The number of contain high content in minerals, particularly iron and rainy days turns around 135 days per year and the period carotene, vitamin B2, vitamin C and vitamin E . The of vegetative growth varies between 229 and 251 days. tubers of sweet potato are rich in starch, sugar, vitamin The valley of Ouémé consists of four municipalities, C, β-carotene, iron and several other minerals [5–7]. namely Dangbo, Bonou, Adjohoun and Aguégué. Our According to , sweet potato tubers proved to be richer survey was conducted in Dangbo and Bonou Munici- in proteins than cassava and the yam tubers. All these palities. Each municipality is divided into several villages features indicate that sweet potato is an important crop among which ten were investigated (Fig. 1). capable of playing a significant role in food security. In These villages were chosen for two main reasons: spite of these assets, sweet potato still remains a margin- alized crop in the development programs of the country. • Favorable zones for sweet potato production. Given Moreover, from 2012 to 2015, the area of production that the needs in water of the sweet potato are esti- of sweet potato compared to other tubers and roots mated at 600 mm of water per cycle, with high quan- declined from 2.21 to 2.01% and a decrease in produc- tity of water at the early stages of crop development tion from 69,829.43 to 55,404.97 tons was also recorded; and adequate temperatures between 22 and 33 °C, henceforth, a slight reduction in production area, i.e., and it is also required between 120 and 210 days for 0.20% and a drastic yield reduction of 20.65% . It has crop development . We can say that the rainfall been basically due to a certain number of factors such conditions and temperature in the survey zone are as pathogens, weevils (Cylas spp.), sweet potato virus propitious to the requirements of the sweet potato disease, low market value tubers harvested by farmers, production; and lack of certified planting materials resistant to abiotic • Areas of high sweet potato production. and biotic elements and modern storage facilities for long-term conservation. Jackai et al.  reported that Sampling and data collection there are losses of millions of dollars annually only due In order to achieve the objectives of this work, the survey to infestation of sweet potato by weevils and these insect was carried out in two (02) phases: an exploratory phase pests are more prevalent in the tropical regions. Based and an in-depth survey phase. on this decline in sweet potato production and taking The exploratory phase consisted in establishing con - into account its high potentiality, it could be important tact with people in charge of CARDER (Regional Action to intensify research efforts to increase its production for Center for Rural Development), the different produc - the benefit of the producers and consumers and sort out ers of the two townships. The contact was established the problem of food insecurity. To this end, this survey through the person in charge of rural development and was conducted in the valley of Benin more precisely in the adviser in crop production representing the ministry the townships of Dangbo and Bonou to analyze the tech- of agriculture in the locality for the list of farmers grow- niques of production systems and marketing of the sweet ing sweet potato. potato by identifying the constraints that prevent the The exploratory survey enabled us to obtain some development of this sector. primary information about sweet potato through Ezin et al. Agric & Food Secur (2018) 7:15 Page 3 of 12 Fig. 1 Geographical localization of the ten villages investigated interview with producers (target group and individual In the in-depth survey phase, a total of 150 producers discussion) selected randomly and observations made were randomly surveyed but due to the heavy infestation in the field. This phase was also of great help for setting of caterpillars and cylas spp. and some pathogens in the proper questionnaire for the in-depth phase. last few years, complete information were obtained only Ezin et al. Agric & Food Secur (2018) 7:15 Page 4 of 12 from 100 producers while incomplete information were as cutting of vines, planting and tuber gathering for stor- obtained from those who abandoned sweet potato pro- age were observed. duction as at the time of the study. Thus, 100 produc - The education level of respondents surveyed is pre - ers with complete information were used in this study. sented in Fig. 2. From the analysis of this figure, most Therefore, the producers were surveyed through inter - of producers did not attend schools and were primary views, participating and/or direct observations and focus school dropouts. group. Qualitative and quantitative data were collected. Table 2 shows the classification of respondents accord - The parameters included sex, age, size of the household, ing to the cultivated areas. From the analysis of the level of education, cropped area, number and types of results, 44% of respondents grew sweet potato on farm- varieties, mode of land acquisition, and types of labor, soil land of 1 to 2 ha, 36% in lesser than 1 ha of land and 20% fertility management, development phase and yield of the of respondents in 3 ha of land. sweet potato. The producers were ranked based on the Figure 3 shows the distribution of the respondents size of areas cropped as follows: cropped area lesser than according to the mode of access to land. The analysis of 1 ha as small producers; between 1 and 2 ha as average the results of Fig. 3 reveals that the mode of access to scale farmers and cropped area greater or equal to 3 ha land the most observed was the inheritance (50%) fol- as large scale producers. As far as the constraints are con- lowed by purchase (30%) and renting (20%). It should be cerned, they were ranked based on farmers’ percentage. noted that women were less involved in farm activities due to the fact that they are not entitled to land heritage Data analysis in Africa context, mainly because of their significant roles The collected data in survey sheets were examined and in the household affairs. codified and then entered into Microsoft Excel. The Table 3 shows the different types of labor used by pro - descriptive statistics with the aid of Minitab software ducers. The analysis of the results of this table reveals was computed and averages, frequencies, minimum and that the most observed was labor (75%) followed by fam- maximum of some parameters such as sex, age, size of ily workforce (25%). Mutual aid was also observed in the household, the level of education and the availability complement of family workforce. Family labor was only of the land were determined. used during weekend and holidays. Male producers made use of the two types of labor whereas female producers Results Profile of farmers The producers of sweet potato investigated in the town - ship of Bonou and Dangbo were all native (40% were from sèto and 60% from Whémé). Majority of sweet potato producers in study area were men (56%) with ages between 40 and 60 years while those of less than 40 years and older than 60 years were 12% (Table 1). This impor - tant number of men in sweet potato production could be justified by the toughness of the works on the vertisols. About 80% of respondent households were within the range of working age (< 40 to 60 years old), whereas only 12% of them were elder (> 60 years old). Despite the high Fig. 2 Educational level of producers investigated number of men, an increase in women in some tasks such Table 1 Socio-demographic characteristics of respondents according to their age, sex, ethnic group and townships Township Age Ethnic group < 40 40–60 > 60 Sèto Whémé M F M F M F Bonou 10 0 32 10 8 0 60 Dangbo 2 2 24 8 4 0 40 Total 12 2 56 18 12 0 40 60 Frequencies (%) 12 2 56 18 12 0 40 60 Ezin et al. Agric & Food Secur (2018) 7:15 Page 5 of 12 Table 2 Typology of producers according to the areas cultivated Areas cultivated Sex Townships Total Bonou Dangbo Number Fre % Number Fre % Number Fre % < 1 ha Male 16 16 8 8 36 36 Female 4 4 8 8 1–2 ha Male 20 20 2 2 44 44 Female 4 4 18 18 > 3 ha Female 14 14 4 4 20 20 Female 2 2 0 0 Total 60 60 40 40 100 100 22%. The main constraints to loan access are several for - malities to complete at the banks, the long distance that separates these banks from producers, the non-return of the loans by some farmers in past and the high interest rate. Sweet potato production and storage: constraints and adaptive strategies The propagation by cuttings was performed 2 weeks after the application of herbicides. It should be noted that problem of input supply arises in the study area. The problem of weedicide and insecticide supply in the study Fig. 3 Distribution of producers according to the mode of land access area could be justified by the long distance between the area of cultivation and CARDER headquarter especially because of the river of Ouémé separating the two sites. Some producers buy an important quantity (liters) of pes- Table 3 Different types of labor used by the producers ticides that is more than what is needed for their farms Labor Number Frequency (%) and resell at high price to other producers. The cost of a liter of the inputs ranged between 4000 and 5000 FCFA Labor 75 75 (US $8 and US $10) when bought from CARDER and Family aid 25 25 5000–6000 FCFA (US $10–12) when bought from local Total 100 100 sellers. The majority of farmers used sweet potato plant - ing material from their previous crop or from their neighbors. often dependent on their husbands for help and occa- The land preparation consists in cutting weeds with the sionally used labor to supplement the family assistance. aid of sickles on the ridges of previous season. Accord- It should also be noted that in addition to the high cost ing to the majority of producers, this allows the decom- paid to manpower, producers also provided foods to the position of weed residues which are sources of nutrients workers during the period they carried out the work in to the growing sweet potato plants for better productiv- the field. ity. Moreover, it also helps to manage the harmful pests Capital funds invested in the production of sweet by destroying their habitat and also by preventing the potato by farmers include their own funds and loans. resumption of the adventitious tubers. To facilitate the Their own funds were from other agricultural-related work, the producers applied SHARP herbicide at a rate of activities. Producers took loans at interest from differ - 480 g/L, 2 weeks before land clearing. ent agricultural banks such as CLCAM (Local Bank for Irrigation (Fig. 4) was applied during the dry season to mutual agricultural loan) and ASF (Association of Finan- facilitate the plowing and water supply to plants. About cial Services), to be able to face labor payment and other (80%) of producers interviewed applied irrigation during input activities. The loans were repaid at interest rate of dry season for out-season production. Ezin et al. Agric & Food Secur (2018) 7:15 Page 6 of 12 Table 4 Traits of varieties of sweet potato grown in Bonou and Dangbo Morphotypes Color skin Water content Ability for storage Adjlè White Moderately low Good Atakan White Moderately low Good Ahotonon Red Moderately low Poor Amiwèdé White Low Good Zohoun Red Moderately low Good Vobodouaho White High Poor Adogoun White Moderately low Poor Minché White Moderately low Poor Fig. 4 Land irrigation The water content is based on farmer perspective All producers investigated (100%) plowed their lands “Vobodouaho” means you can be in debt without wor- manually and planted on ridges. The height of the rying. According to the producers, this variety by its ridges was 30 cm; the distance between the ridges was high productivity enables them to pay their debts. 50–80 cm. The length of each ridge ranged from 3 to According to the producers surveyed, the harvests were 6 m. performed at harvest maturity but there was also early Results on cropping systems indicated that most of harvest which was done at physiological maturity due to farmers did not practice mixed cropping. According to flooding. The potato reaches its physiological maturity the producers, the association of sweet potato to other when the stems and leaves began yellowing and leaves crops would affect the productivity and the expected started dropping. The harvest usually starts in April and yield of sweet potato due to the competition for nutri- ends in August. When it rains and the ridges are half ents, sun, air etc. They did not also practice crop rota - flooded, the producers immediately harvest them. The tion. Weeding was carried out at least twice, this men carried out the harvesting and the women picked depends on the proliferation of weeds, but some pro- up with a basin and then transport them to the place of ducers did a single weeding because of the high cost of packaging. labor. The majority of respondents did not use chemical The producers surveyed have several storage methods. fertilizers. Producers did use some methods to main- A first method consists on gathering the tubers in heaps tain soil fertility such as the burying of weeds and crop and covering them with plant debris (Fig. 5). The storage residues in the soils. period varies between 1 and 2 months if the ridges were The planting material used was obtained from at not flooded before harvest. A second method consisted least 5 months old plants. The lengths of the planting in packaging the sweet potatoes in the bags and cover- material vines varied between 30 and 40 cm and were ing them with vegetable debris (Fig. 6). None of the pro- immediately planted at a depth of 20 cm with a den- ducers interviewed had sophisticated facilities for long sity of 33,333–46,667 plants per hectare. When the period of storage. ridges to be made for planting were not ready, the vines All the producers surveyed estimated that for two were kept in moist soils under the shades in order to ridges (of 6 m long each) an average of 55 kg was har- maintain their viability. The majority of respondents vested but in case of pest attack at least six ridges of conserved the planting materials in the fields for next sweet potato were required before obtaining the 55 kg planting. It should be noted that none of the producers which reduced the average yield to about 6.5 tons/ha. interviewed used certified planting materials because Therefore, the average yield of sweet production per hec - breeders and seed agencies did not make this available tare without disease and pest infestation and at optimal to them. conditions was 15.125 tons. Table 4 presents the eight varieties of sweet potato The main constraints were diseases and insects viz used by farmers and their different traits. The variety black rot, Alternaria and caterpillars (Lepidoptera larva), “Vobodouaho” was grown by all producers interviewed. which cause serious damage to the tubers (Fig. 7). This The choice of this variety is based on the following: insect is called “Hlo” in local language. The causal agent preferred by consumers, short cycle of 4 months, high of black rot was identified as Ceratocystis fimbriata while yields and big tubers when compared to other varieties. that of Alternaria species was Alternaria solani and Ezin et al. Agric & Food Secur (2018) 7:15 Page 7 of 12 attacked. Acraea acerata attacked the leaves by perforat- ing them. In the dry season, this caterpillar caused tre- mendous damage and resulted in poor yields (Fig. 7). To control this insect, the producers used active ingredient of super action insecticides and super cydim containing cypermethrin. It should be noted these insecticides are normally used for other market gardeners, which are not specific to sweet potato pests. None of these pesticides control Cylas puncticollis as reported by the farmers. Further studies must then be initiated to find the most suitable pesticides and other control measures for the control of sweet potato pests and diseases. Other constraints identified by farmers surveyed were high temperatures, high moisture content of tubers, flooding of potato fields and late harvesting. Producers also listed weeds as serious constraints in the Ouémé val- ley where the lands are rich in nutrients. Some producers used herbicide SHARP 480 SL as control measures. Fig. 5 Heaping of sweet potatoes on the farm Table 5 presents the various constraints in order of importance as perceived by the producers and the adap- tation strategies developed. The adaptation strategies developed by the producers aim at reducing the effects of these constraints for a good productivity of sweet potato. Marketing of sweet potato products and constraints Producers marketed their sweet potato produces in sev- eral local markets, namely Dangbo, Ouando (Porto- Novo), Tatonnonkon, Dasso, Assrossa, Bonou and Dantokpa (Cotonou). But none of the producers did export their products to the subregion and international markets. The marketing options include direct sales to consumers and selling to wholesalers or retailers. During the periods where sweet potato tubers are much more available, the supply becomes greater than the demand. This causes the producers to sell their products at a low price. This is due to the lack of storage facilities and the financial needs of producers. The sweet potato tubers Fig. 6 Storage in bags of sweet potatoes were sold either in a basin (Fig. 9) or packed in bags and transported by canoes (Fig. 10) to the markets. The bas - ket was between 3500 and 4000 FCFA and the bag was insect was identified as Acraea acerata commonly known 6000 FCFA. There is rapid growth in demand for sweet as “wanvi” in local language by producers. Another insect potato in urban areas because it is fried every afternoon species identified was Cylas puncticollis, a weevil, known in every corner of the cities and it is also boiled but in as vâ in local language, and it does cause galleries (hol- rural areas it is boiled and pounded together with yam lows) on tubers (Fig. 8). It causes the root losses result- and eat as food with sauce. This has created huge oppor - ing in crop failure. It also leads to poor quality of tubers tunities to sell and market sweet potato in urban and that are no longer accepted in the market. Ceratocystis rural areas. The main constraints in marketing sweet mbr fi iata caused the yellowing of young leaves and the potato tubers is due to the infestation of some tubers by blackening of the underground parts of the stem while insect pests which lower its quality and nutritional value it caused circular holes on the tubers. Alternaria solani and therefore make the consumers not to be interested showed brown rings on the leaves and black lesions on in it because oftentimes some farmers fail to remove the the petiole and stem. The matured leaves were the most damaged tubers from the healthier ones. But most often Ezin et al. Agric & Food Secur (2018) 7:15 Page 8 of 12 bought the wholesale from wholesalers; they were trad- ers and they bought in large quantities at a price that could be estimated at 5000 FCFA/basket. The retailers bought agricultural products at relatively high prices (7000 FCFA/basket) from semi-wholesalers compared to the purchase price practiced by semi-wholesalers from the wholesalers and the wholesalers from producers. They were market traders. The consumers bought from retailers for their own food needs. They bought at a rela - tively higher price. The semi-wholesalers sell 4 to 5 tubers per heap (200–400 FCFA) to the consumers. The produc - ers preferred to sell their products to wholesalers instead of going to the market in order to avoid paying transport fees. The transporters were responsible for transporting Fig. 7 Decayed tubers due to the attack of caterpillar products from the fields to the markets. Discussion The leaders of households interviewed were mostly males as the case in other African countries. Our results are similar with those of  who reported that over 60% of the farmers surveyed were men in their study in Kenya. 55% of the respondents were illiterate and only 35% com- pleted primary education (Fig. 2). This is below the mean national literacy level of adults to adopt some agricultural technologies. So, the illiteracy of farmers could be the rai- son behind some poor agricultural practices observed in the field, and the low yield recorded year after years. They could not read the instructions on the label on the inputs used unless they are associated with somebody who can help. But these producers were experienced enough to apply some good agricultural practices. These results are not consistent with those of  who reported that most (54.2%) of the interviewed households completed pri- mary education in southern Ethiopia, same results were obtained by . The production of sweet potato in the studied areas Fig. 8 Some sweet potato tubers attacked by Cylas puncticollis is still traditional. Crop production practices are car- ried out manually using rudimentary tools such as hoe, cutlass. The main difficulty was related to the prepara - it is sold at low price due to the low marketable root tion of the soil by making ridges, a difficult task on clay yields, which lead to low income. soils of the areas of study due to the rudimentary tools used. The 88% of respondents within the range of work - Value chain of sweet potatoes ing age possess the physical strength required to face The actors involved in the value chain are: producers, the challenge of sweet potato production with the use wholesalers, semi-wholesalers, retailers, transporters of rudimentary tools. Under these conditions, the use of and consumers (Fig. 11). The producers were the sweet modern tools for the production of sweet potato should potato farmers. They were involved in field production be explored in order to reduce the difficulties associated and they do receive input supply from CARDER and with sweet potato production. In another words, the use informal agencies who bought their inputs from Nige- of oxen and tractors would be of great help in plowing, ria. After harvest, the sales were carried out in the fields. weeding and harvesting, which will reduce root dam- The wholesalers were big traders of the locality; they ages especially during harvesting. In relation to plant- bought directly from the producers and the basket of ing, there is always problem of plant material scarcity, sweet potato is sold at 3500 FCFA. The semi-wholesalers i.e., lack of vines or seed tubers. Producers often do not Ezin et al. Agric & Food Secur (2018) 7:15 Page 9 of 12 Table 5 Constraints in order of importance and coping strategies Constraints Adaptive strategies Rank % farmers Climate hazards (flood and submergence) Temporary abandonment of fields 1 39 Absence of modern’s equipment for production Use of available means and materials of production 2 20 Lack of adequate methods for pests management Use of chemical products intended to market gardening 3 10 to reduce pest damage Scarcity and expensiveness of labor Use of family workforce, labor and mutual aid 4 8 Toughness of activities High use of labor 5 7.5 Absence of best storage methods for a long time Immediate sale of tubers after harvest 6 6 Inexistence of road system for tubers transport to the market Using pirogue to transport sweet potatoes 7 5.5 Slump in sales during harvest of tubers Early harvest of tubers and choice of short-cycle varieties 8 3 ( Vobodouaho et minché) Lack of training and aid to the members of their associations and Use of traditional practice for the production 9 1 from agricultural extension agents have planting material for the next growing season. This hectare for better productivity. The average yield of sweet problem is exacerbated by the flood from the overflow - potato ranges from 6.5 tons to 15.125 tons/ha. The high ing of the river which invades their field coupled with the yields were obtained with adequate control measures lack of supervision and training. Therefore, a training of and were of 275 basins or 15.125 tons per ha which was producers is necessary in order to provide all the tech- above the average yield in other African countries such as nical assistance for the best cultivation of the crop , Kenya and Ethiopia.  in their review on sweet potato particularly on the techniques of planting and multiplica- production constraints reported that the average yield of tion of cuttings and their conservation for next growing sweet potato in Ethiopia was 8 tons/ha but below 18 tons/ season. Sweet potato was mainly planted on ridges and ha in the Asian countries. This indicates that the produc - the density of seedlings was about 33,333–46,667 plants tion constraints need to be properly addressed in order to per hectare. These values were relatively higher than the improve the productivity of sweet potato in Benin so as ones recommended by , which is 30,000 plants per to better the yields obtained by Asia countries. Furthermore, the cultivation of sweet potato crop is facing with other difficulties such as weeding. This is a serious problem due to the nature of the soil (clay) and the lack of manpower in the areas of study. The results of our surveys showed that some producers, consider- ing the high cost of labor, reduced the number of weed- ing during the sweet potato development cycle. The decline in yield observed in some respondents’ fields was due to the lack of weeding. Our results are consist- ent with those of  who reported yield losses of 22% in India and 57% in Africa from non-weeded farms of sweet potato. Another constraint is related to the attack of pathogens and insect pests such as black rot, Alter- naria blight, cylas spp. (weevils) and caterpillars which cause enormous damage and reduced the market value of the produce. This could be due to the single-crop farm - ing adopted year after year in the areas. Tefera et al.  have also reported sweet potato virus disease as a major constraint of sweet potato production in Ethiopia and they also, reported that Alternaria blight was a constraint even though not serious. As a control measures,  in Nigeria reported that a mixture of 50 mL of neem seed oil extract and 30 mL of diazinon in either 2 or 10 L of Fig. 9 Basin of sweet potato tubers water and cuttings dipped for 30 min (unconventional Ezin et al. Agric & Food Secur (2018) 7:15 Page 10 of 12 or crop associations to avoid the buildup of diseases and insects of sweet potato in the farms. According to , these practices have many advantages in optimizing pro- duction and maintaining soil fertility. In the same vain,  also reported the need to improve and build the capacity of farmers. They further stated that the lack of resistant varieties as well as disease- and pest-free sweet potato planting materials were the major hindrance to pest and disease control. Henceforth, breeders need to identify resistant varieties as well as promote produc- tion of clean seed to improve sweet potato production. This is consistent with the study of  on resistance gene expression on sweet potato virus resistance. The farmers did not apply mineral fertilizers to sweet potato plants due to the fact that they considered their fields fertile. They stated that there is frequent inundation in every rainy season due to the overflow of the rivers and drought in dry season which help in maintaining the fer- Fig. 10 Transport of sweet potatoes tility of their soils. Producers are also confronted with water problems because of the poor distribution of rain- fall in recent years due to climate change, which hampers the development of seedlings and do affect negatively Producers the productivity. After the harvest, producers were com- pelled to sell their produces at low price because of the storage problem, i.e., the difficulties of conservation due to lack of adequate facilities and the recalcitrant nature of Wholesalers sweet potato tubers. The different methods of short stor - age observed by respondents are the collection of tubers by women during harvest and put them together in heaps Semi-wholesalers and covered them with plant debris as showed in Fig. 5. The storage period varies between 1 and 2 months if the ridges are not flooded before harvest. A second method consists in conditioning the sweet potatoes in the bags Retailers and protecting them with vegetable debris (Fig. 6). The storage period using this second method is just 7 days for the sweet potatoes to be sold to avoid rotting. Sweet Consumers potato producers really need better strategies that will allow them to better conserve their crops and sell high- Fig. 11 Sweet potato value chain quality sweet potatoes under the best storage practices, especially when demand is high in the market and for weevil control method) controlled Cylas puncticollis by high income. For sustainable field preservation in order 35.5%. Producers used the sweet potato planting materi- to avoid insect attack,  suggested the cutting of all the als from the previous crop because of the non-availability potato biomass at the end of the rainy season, the remak- of certified planting materials of sweet potato tolerant ing of the ridges so as to damage the eggs of the weevils to pathogens and pests in the country. This indicates and covering the exposed tubers and the regrowth should the reason why there are disease and pest infestations in be regularly cut. The tubers are thus kept in the field the field and low yields. Fuglie  carried out a survey until the beginning of the rains. This practice also makes work on constraints across many countries and similarly it possible to better conserve the tubers and to sell them found that lack of clean and enough planting material during periods of high demand . Hue and Low  was a major constraint in most of African countries. The also reported that many works have testified about the respondents’ training could help limit the number of suc- significant effectiveness of Bacillus thuringiensis in con - cessive crops on the same plot and adopt crop rotation trolling diverse pests of sweet potato including cylas spp. Ezin et al. Agric & Food Secur (2018) 7:15 Page 11 of 12 Consent for publication Conclusion The respondents were informed that their opinions were to be published in a Sweet potato is a crop with high nutritional value and scientific paper and gave their approval. is classified as the most energy-rich tuber. The findings Ethics approval and consent to participate of this work reveal that the lands are fertile to grow No ethical approval was needed for this study. Prior to data collection, partici- sweet potato in the area but it is yet to be grown in a pants gave oral consent to participate in the study. large scale as the farm size varies from < 1 to > 3 ha. Funding The main constraints are flooding, diseases and insect Not applicable. infestations which reduce the productivity of sweet potato in the area of study. Farmers don’t have access to Publisher’s Note certified planting materials resistant to pathogens and Springer Nature remains neutral with regard to jurisdictional claims in pub- insect pests. Therefore, appropriate measures need to lished maps and institutional affiliations. be taken for their proper control in order to increase Received: 29 June 2017 Accepted: 24 January 2018 the return of farmers. This is followed by poor tubers due diseases and insects, low market price, scarcity and high cost of labor, and the lack of better conservation methods for a long time, low yield. Additionally, farm- References ers don’t benefit from their labor when considered the 1. Adégbola P. Analyse de la filière patate douce au Bénin, PDRT/MAEP. Rap - profit made by other actors along the value chain and port final 2003; 162p. this need to be tackled by policy makers so as lessen 2. Egbe OM, Afuape SO, Idoko JA. 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Occurrence and intra-specific the manuscript. VE, QF, BFC, EMGK and AA supervised data analysis and variation of sweetpotato weevil (Brentidae: Coleoptera) in relation to its revised the manuscript. All authors read and approved the final manuscript. potential spread in southern United States of America and the Caribbean. In: ISHS acta horticulture 703: II international symposium on sweetpotato Authors’ information and cassava: innovative technologies for commercialization, p. 197–204, RHB and CMIK are Research Assistants at University of Abomey-Calavi. VE and International Society for Horticultural Science, Leuven, Belgium; 2006. QF (PhD) are lecturers in Plant breeding and genetics at University of Abomey- 10. Agueguia A, Fontem DA, Mbahe RE, Mboua JC, Mouen M, Ngo Som J, Calavi, Department of Crop Science. BFC is a lecturer in food science at Poné Kamdem D, Tchuanyo M, Zok S. La patate douce: un potentiel trop University of Abomey-Calavi. 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HortScience. 2007;42:1200–6. ment: a review. Psyche. 2015, Article ID 849560. http://dx.doi. 20. Degu G, Markos D, Bekele A, Kassie M. Community survey and on-farm org/10.1155/2015/849560. trials for conservation agriculture to enhance adoption and its impact. Int J Sci Eng Res. 2013;4:1225–35. Submit your next manuscript to BioMed Central and we will help you at every step: • We accept pre-submission inquiries • Our selector tool helps you to ﬁnd the most relevant journal • We provide round the clock customer support • Convenient online submission • Thorough peer review • Inclusion in PubMed and all major indexing services • Maximum visibility for your research Submit your manuscript at www.biomedcentral.com/submit
Agriculture & Food Security – Springer Journals
Published: Jun 1, 2018
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