Asian Journal of Agricultural Research

Year: 2020 | Volume: 14 | Issue: 2 | Page No.: 41-48
DOI: 10.3923/ajar.2020.41.48

Sweetpotato Production Practices and Cylas species Management Options in Southern Ghana

Yaw Danso , Kingsley Osei, Joseph Adomako , Umar Sanda Issa, Ernest Baafi , Bismark Abugri and Hugues Baimey

Abstract: Background and Objective: Cylas species infestation is a serious pest threat to sustainable sweetpotato production in Ghana. For integrated Cylas species management, exploiting the potential of entomopathogenic nematodes, noting and appreciating sweetpotato farmers’ production practices is essential. Sweetpotato production practices and Cylas spp. management options in some major growing areas of southern Ghana were assessed. Materials and Methods: Farmer-level structured questionnaire was designed, pretested and used to collect information from 270 respondents employing both qualitative and quantitative techniques. Results: Seventy-nine percent of the farmers cultivated local sweetpotato cultivars. Eighty-six percent practiced sole cropping while 47% managed their own planting material from the previous crop. Sixty-nine percent cited Cylas species as the most important sweetpotato pest. Ninety-seven percent responded positively to awareness of Cylas spp. infestations in sweetpotato production. Major Cylas species management options indicated by farmers were; insecticides application, early harvesting, earthing up, crop rotation and weed control in order of significance. Seventy percent (70%) did not manage Cylas species infestations in sweetpotato production. Conclusion: Cylas spp. management with synthetic farm insecticides must be discouraged on grounds of human and environmental health concerns. Biological control, which involves incorporating entomopathogenic nematodes should be encouraged in an integrated pest management system for environmental friendliness.

Keywords: weevil pests, Entomopathogenic nematodes, IPM, Ipomoea batatas, environmental friendliness and Biological control

INTRODUCTION

Sweetpotato (Ipomoea batatas L. (Lam) provides good ground cover and prevents soil erosion¹. It has high β-carotene content than any other root and tuber crop². It has numerous medicinal uses which include managing menstrual problems and osteoporosis³. Sweetpotato is also used in industrial starch production⁴, microbial hydrogen⁵and ethanol fuel production⁶.

However, high sweetpotato crop productivity is constrained by Cylas spp. infestations. Cylas spp. is the most serious biotic threat to sustainable sweetpotato production worldwide. Tuber losses between five and 97% have been recorded in areas where Cylas species infestations occur⁷. There is often a positive relationship between vine damage or weevil population density and tuber damage. Major symptom of a heavy infestation is yellowing of the vines and tuber mining by Cylas species larvae. Infested storage roots are often riddled with cavities, spongy in appearance and dark in storage root flesh color. This greatly reduces the food and market value of the economic harvest. The tunneling damage caused by Cylas species larvae predisposes the storage roots to other soil-borne pathogens. Even low levels of the larvae feeding on tubers induce a chemical reaction that imparts a bitter taste and bad odor to the storage roots⁸. The damage ultimately renders sweetpotato storage roots unwholesome for human and farm animals’ consumption.

Entomopathogenic nematodes have the potential for practical biological suppression of Cylas spp. Strains of Steinernema carpocapsae (Nematoda: Steinernematidae) and Heterorhabditis bacteriophora (Nematoda: Heterorhabditidae) penetrate the soil and storage roots to infest and kill storage root damaging Cylas species larvae⁷. Entomopathogenic nematodes occur naturally in cropland soils and the infective juveniles are often persistent; remaining active for up to four months. In some cases, entomopathogenic nematodes are more effective than insecticides at reducing damage caused by Cylas species in sweetpotato production⁹. Integrating entomopathogenic nematodes in sustainable Cylas species management, noting and appreciating sweetpotato farmers’ production practices is essential. In this study, sweetpotato production practices in some major growing areas of southern Ghana were assessed especially with regards to options for indigenous management against Cylas species.

MATERIALS AND METHODS

A farmer-level structured questionnaire was used to collect data on sweetpotato production practices from farmers employing both qualitative and quantitative techniques¹⁰. The questionnaire was administered in nine major sweetpotato growing districts in southern Ghana. The study areas covered three regions; Central, Volta and Eastern (Table 1). Two hundred and seventy active sweetpotato farmers were purposely selected as respondents across nine districts (30 respondents per district). Farmer selection was done in collaboration with local Agricultural Extension Agents of Ministry of Food and Agriculture in the respective districts. The survey was conducted between February and May 2017. Data collected were analyzed with SPSS and results presented in tables and graphs.

RESULTS

Across the districts, 71% of the respondents were males (Fig. 1). In the Fanteakwa and Ketu North Districts, 54 and 10% of the farmers respectively, had no formal education (Table 2). In the Ketu North district, 35% of the respondents had cultivated sweetpotato for over 20 years whilst 20% in the Upper Manya Krobo and Upper West Akyem districts had the same wealth of experience in sweetpotato cultivation (Table 3). Sixty-three percent respondents were cultivating sweetpotato primarily for cash income whilst, 26% cited “quick returns’’ or “early maturing” as the most important reason for growing the crop (Fig. 2).

Averagely, 79% of respondents cultivated local sweetpotato cultivars (Fig. 3). None from Twifo Heman Lower Denkyira district cultivated sweet potato crop above five acres (Table 4).

Land preparation methods employed for growing sweetpotato were flat ploughed, mounds and ridges. In the Akatsi South, Komenda Edina Eguafo Abirem and Upper West Akyem districts, none used flat ploughed to cultivate sweet potato. In the Upper West Akyem district, all the farmers used mounds to cultivate the crop, whilst none used ridging in the Upper Manya Krobo district (Table 4). Six, 8, 16 and 4% were growing Santom Pona, Sauti, Ogyefo and Tek Santom improved sweetpotato varieties, respectively (Fig. 4).

In the Ketu South and Fanteakwa districts, all the farmers practiced sole cropping whilst 93%, 93% and 94% farmers in the Ketu South, Ketu North and Upper West Akyem districts respectively, practiced same (Table 5).

Averagely, 47% of respondents managed their own sweetpotato planting material from the previous crop. Almost 18%, 23% and 12% got their supply from the Ministry of Food and Agriculture, friends and open market, respectively (Fig. 5).

Ninety-seven percent (respondents) did not subject their sweet potato planting material to any form of chemical treatment prior to planting to ward off pre-existing pests and pathogens (Fig. 6).

Farmers responses to major sweetpotato pests across the districts were; weevils (69%), caterpillars (14%), grasshoppers (6%), millipedes (4%), viruses (3%), centipedes (1%), beetles (1%), whiteflies (1%) and termites (1%) (Fig. 7).

Ninety-seven percent of the farmers responded positively to awareness of sweetpotato Cylas species infestations (Fig. 8).

Seventy percent of the respondents never managed Cylas species infestations in sweetpotato production (Fig. 9).

DISCUSSION

Majority (71%) of the respondents across the study area were males. Illiteracy rate found among the sweetpotato farmers was below the 46% Ghanaian adult illiteracy rate as cited by Ghana Education Service in 2012. Sixty-six percent of farmers who had adopted improved sweetpotato cultivars were growing Apomuden variety (Orange Fleshed Sweetpotato, a precursor for pro-vitamin A). This may be due to cultural norms that designate sweetpotato as men’s crop in the study areas or the drudgery nature of land preparation which may be unbearable for prospective sweetpotato women farmers. In a similar study involving 120 sweetpotato farmers in four districts of Ghana, 69% of the respondents were males¹¹. Adoption of improved agricultural practices is positively correlated with education, whether formal or informal¹². Sweetpotato farming was found to be a lucrative venture as 63% of respondents were cultivating the crop primarily for cash income. However, the profit margin for sweetpotato traders far outweighed that of the farmers due to lack of storage and processing facilities which compelled the farmers to sell off their produce quickly at the farm gate¹¹. Land preparation methods recorded agreed with the study of others who posited that sweetpotato in southern Ghana was planted mainly on constructed mounds¹³. Sweetpotato farmers used other land preparation methods but said that planting was easier on mounds than on ridges. Mounding was prominent in sweetpotato production¹¹ and most preferable because of the easier harvesting of the produce. Land preparation for sweetpotato cultivation in the southern and middle belt of Ghana consisted of bush burning or tractor ploughing after which hoes and or mattocks were used to prepare mounds^14,15.

Seventy percent of the 120 sweetpotato farmers were aware of improved sweetpotato cultivars out of which 21% cultivated one or more of the improved cultivars¹¹. However, earlier findings by others reported non-availability of improved sweetpotato cultivars in the southern and middle belt of Ghana¹⁴. In the current study, the use of local sweetpotato cultivars for cultivation was common. Similarly, most sweetpotato farmers didn’t have access to improved planting materials in southern Benin¹⁶. All the improved sweetpotato planting materials encountered in the current study were developed by CSIR-Crops Research Institute of Ghana, except Tek Santom which was developed by Kwame Nkrumah University of Science and Technology (KNUST), Ghana. Similarly, Santompona, Sauti, Faara, Okumkom and Apomuden were recorded as improved sweetpotato cultivars being cultivated by farmers in four districts of Ghana¹¹. Sole cropping was the most popular sweetpotato cropping system practiced among the 120 sweetpotato farmers¹¹. As was found in the current study, Cylas species and caterpillars were reported as major insect pests that damaged sweetpotato in Dangbo and Bonou townships of southern Benin¹⁶. Cylas species was also found to be a common pest infesting sweetpotato in Ghana¹¹.

Significantly, farmers reported of six major sweetpotato production practices with no mention of Cylas species management¹¹. There is reported lack of adequate methods for managing pests and diseases in sweetpotato production in Benin¹⁶. In the current study, 70% of the respondents did not practice any management options against Cylas species infestations. On the contrary, insecticides were used to control insect pests in sweetpotato production in southern Benin¹⁶. Actellic 50EC insecticide was reported to be commonly used to manage Cylas species in the Twifo-Ati Mokwa district of Ghana¹¹.

Subsequently, similar studies must be conducted in other major sweetpotato growing areas in other regions of Ghana to give a broader picture of cultivation practices especially with regards to Cylas species management. This study would guide Agricultural Extension Workers and other relevant stakeholders on the dissemination of improved sweetpotato production practices to promote integrated management of Cylas species in sweetpotato production, highlighting the potential of entomopathogenic nematodes as biological control agents. Hence, it is recommended that sweetpotato farmers should contact their Agricultural Extension Workers in their communities on improved sweetpotato production practices to increase the productivity of the crop. Some of the sweetpotato farmers were highly illiterate across the study areas. This made analyzing some of their responses tedious. Also, some of the respondents were reluctant to respond to the questions asked for fear that nothing would come out of the study just like other earlier research works.

CONCLUSION

For sustainable high sweetpotato crop productivity, Cylas species must be managed effectively. Cylas species management with synthetic farm chemicals must be discouraged on grounds of human and environmental health concerns. Biological control, especially employing entomopathogenic nematodes should be encouraged in an integrated pest management system for environmental friendliness. Agricultural Extension Agents, Crop Scientists and relevant NGOs should informally educate sweetpotato farmers on improved production practices that would promote biological control of Cylas species to minimize reliance on synthetic farm chemicals.

SIGNIFICANCE STATEMENT

This study discovered that Cylas species management that can be beneficial for increased sweetpotato crop productivity is regrettably unpopular in sweetpotato production in Ghana. This study will help researchers to uncover the critical areas of exploring entomopathogenic nematodes in an integrated management system against Cylas species in sweetpotato production that many researchers were not able to explore. Thus, a new theory on applying entomopathogenic nematodes in Cylas species management may be arrived at.

ACKNOWLEDGMENTS

The authors express profound gratitude to Bill and Melinda Gates Foundation (BMGF) for the financial assistance to carry out this work. The Agricultural Extension Agents of MoFA, Ghana who identified the respondents and led the research team in the various districts are also acknowledged.

REFERENCES