ON FARM AND POST-HARVEST MANAGEMENT OF MANGO STONE WEEVIL 

(Sternochetus mangiferae F.) 

 

 

This thesis is submitted to the  

UNIVERSITY OF GHANA, LEGON  

GRADUATE SCHOOL OF NUCLEAR AND APPLIED SCIENCES 

COLLEGE OF BASIC AND APPLIED SCIENCES 

  

DEPARTMENT OF NUCLEAR AGRICULTURE AND RADIATION PROCESSING 

 

 

BY  

EKOW NENYI GYANNDADZE ABOAGYE  

(10701478) 

 

 

IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF  

 

MASTER OF PHILOSOPHY IN RADIATION PROCESSING DEGREE  

(ENTOMOLOGY OPTION)  

 

MAY, 2022 

 

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DECLARATION 

 
I hereby declare that this work is the result of my research and that this thesis has neither in 

whole nor part been presented anywhere for a degree. All authors whose work were cited have 

been duly acknowledged as reference.  

 

 

 Signature    Date:  

EKOW N. G. ABOAGYE 

(Student) 

 

 

 

 

 Signature    Date:  

 DR. MICHAEL YAO OSAE 

(Principal Supervisor) 

 

 

 

 

Signature   Date:  

DR. EBENEZER ATO EWUSIE 

(Co-supervisor) 

  

    

 

 

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DEDICATION 

This is work is dedicated to Jehovah God for keeping me alive. I also dedicate it to my mother 

Madam Lucy Dennis and my brother Mr Nathan Dennis for their remarkable financial and 

spiritual support throughout my studies. God bless you.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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ACKNOWLEDGEMENT 

My profound gratitude and appreciation go to my supervisors Dr Michael Y. Osae, the Director 

of Biotechnology and Nuclear Agriculture Research Institute (BNARI), GAEC and Dr 

Ebenezer A. Ewusie, Senior Consultant and Adjunct Lecturer, Metropolitan Research and 

Education Bureau / Ghana Institute of Management and Public Administration (GIMPA) for 

their guidance and direction throughout the research. May the favour of God be upon you 

always. 

To all the Senior Members and Staff of the Nuclear Agriculture and Radiation Processing 

Department, especially Mr Selorm Ofori who made impactful contribution to this work. I say 

God bless you. Mr Justice Frimpong and Ebenezer Kondo were also phenomenal during the 

data analysis.   

Professor Harry Amoatey the former Head of Department of NARP, Dr Samuel Amiteye Head 

of Department, Dr Fedelis Ocloo Deputy Director BNARI and Professor Daniel Asare your 

advice and encouragement brought me this far. God bless you beyond measure.  

Am also thankful to the executives and members of the Yilo Krobo Mango Famers Association 

(YKMFA). I would be ungrateful if the following personalities are not mentioned Mr Okley of 

Modest Farm, Mr Simon of Enyonam Farm, Mr Benedict Buertey and Brother Kweku of 

Matesco Farm and Ras Ekow of Power of Trinity Farm and Construction Ltd. May you never 

lack.    

     

 

 

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ABSTRACT 

A questionnaire composed of twenty-three (23) open and closed-ended questions was 

administered to thirty (30) mango farmers within the eastern mango enclave to investigate the 

level of mango stone weevil (MSW) infestation within the eastern mango enclave. Data 

obtained from the questionnaire was analysed using the SPSS version 25.0 and presented as 

tables in percentages. Chi-square was used to determine the association between selected 

parameters. The response from farmers revealed that 40.7% of farmers grow only one variety 

of mango and the common variety is Keitt which is cultivated by 33.7% of the farmers. About 

eighty-seven percent of the farmers admitted to the presence of the mango stone weevil on their 

farms. Fifty percent of the farmers were found to be relying on insecticides for controlling the 

MSW. About seventy-seven percent of the respondents viewed the mango stone weevil as a 

major pest because it is a pest of phytosanitary importance. The major mango season was 

considered to have the highest infestation as indicated by 90% of respondents. Responses from 

farmers revealed that 76.7% spend about GH¢2000:00 – 5000:00 per acre every season in 

controlling the mango stone weevil. A survey was conducted during the major and minor 

mango seasons immediately after the questionnaire administration. During the survey, thirty 

(30) farms were visited. On each farm, fifty (50) matured fruits were randomly picked and 

dissected to check whether the seeds are infested or free from weevils. The survey brought to 

light that, the MSW is at its highest level during the major season as compared to the minor 

season. Infestation levels on the average were 23.6% and 19.13% for the major and minor 

seasons respectively. To determine the effect of trunk banding using a sticky band, grease and 

insecticide in the control of MSW, the sticky band proved to be the most efficient method. The 

sticky band had lower fruit infestation levels (i.e., 11.5% for minor mango season and 10.5% 

for the major mango season) which were significantly different from the fruit infestation levels 

of the grease banding for both minor and major seasons. Although an X-ray imaging technique 

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could not capture the image of mango stone weevil within infested fruits, it was able to capture 

the image of damaged cotyledon which resulted from feeding by mango stone weevils. The 

findings of the research showed that the mango stone weevil is persistent in the study area, 

mango stone weevil infestation levels are high during the major mango season, the sticky band 

is more effective in controlling the mango stone weevil and lastly soft X-ray technique can be 

used to detect internal infestation of mango by the stone weevil. These findings would go a 

long way to address the menace of MSW infestation, the efficient and effective method of 

controlling mango stone weevil and a non-destructive method of detecting MSW infestations 

which would improve the fortunes of Ghana in the export of fresh mango fruits.    

 

 

 

 

 

 

 

 

 

 

 

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TABLE OF CONTENT 

Number Content Page 

 Declaration  i 

 Dedication ii 

 Acknowledgement iii 

 Abstract  iv 

 Table of Content vi 

 List of Tables x 

 List of Figures xi 

 List of Appendices xiii 

 List of Abbreviations xiv 

 CHAPTER ONE 1 

1.1 Introduction. 1 

1.2 Problem Statement. 4 

1.3 Justification. 7 

1.4 General Objectives. 8 

1.5 Specific Objectives. 8 

 CHAPTER TWO 9 

2.0 Literature Review. 9 

2.1 The Mango Crop. 9 

2.1.1 Botany. 10 

2.2 Mango Varieties. 11 

2.2.1 Haden. 12 

2.2.2 Keitt. 13 

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2.2.3 Kent. 14 

2.2.4 Palmer. 15 

2.2.5 Tommy Atkins. 16 

2.3 Mango production in the world. 17 

2.3.1 Mango production and distribution in Ghana. 18 

2.4 Economic importance of mango. 20 

2.5 Constrains of mango production. 23 

2.5.1 Pest and Diseases. 24 

2.6 The mango stone weevil. 26 

2.6.1 Biology and ecology of the mango stone weevil. 26 

2.6.2 Taxonomy, description and distribution of the mango tone weevil. 28 

2.6.3 Importance of MSW on mango production and export in Ghana. 31 

2.6.4 Management of mango stone weevil. 32 

2.6.4.1 Chemical control method. 32 

2.6.4.2 Biological control method. 33 

2.6.4.3 Cultural control method. 34 

2.6.4.4 Pest-resistant varieties. 34 

2.6.4.5 Physical and mechanical control. 35 

2.6.4.6 Quarantine and phytosanitary measures. 36 

2.6.7 Detection of mango stone weevil within the fruit. 

CHAPTER THREE 

37 

40 

3.0 Materials and methods. 40 

3.1 Study area. 40 

3.2 Knowledge, attitude and practices mango farmers use on mango stone 

weevil and its management.  

42 

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3.3 Survey of mango stone weevil infestation. 42 

3.4 Evaluation of different management methods against the MSW.  43 

3.4.1 Sticky band  44 

3.4.2 Chlorpyrifos (Dursban 4EC) 45 

3.4.3 Grease Banding  46 

3.5 Non-destructive detection of internal infestation of mango stone weevil.  47 

3.6 Data analysis. 48 

 CHAPTER FOUR 49 

4.0 Results. 49 

4.1 Knowledge, attitude and practices of mango farmers towards MSW 49 

4.1.1 Demographic characteristics of mango farmers used in the survey 49 

4.1.2 Farm size and mango varieties on farms were captured in the survey. 51 

4.1.3 Farmer’s knowledge on pest and pest control.    53 

4.1.4 Pest and pest management on mango farms in the study area. 55 

4.1.5 Finance of mango farmers covered in the study area 59 

4.2. Level of MSW infestation within the eastern mango enclave.  62 

4.3 Effect of different treatments in controlling the mango stone weevil. 65 

4.4 The non-destructive method of detecting MSW using soft X-ray 

technology. 

67 

 CHAPTER FIVE 69 

5.0 Discussion 69 

5.1 Demographic characteristics of mango farmers in the study area. 69 

5.2 Farm size and mango varieties cultivated. 71 

5.3  Farmers’ knowledge of pests and pest management. 72 

5.4 Pest and pest management on mango farms. 74 

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5.5 Finances of mango farms 77 

5.6 Mango stone weevil infestation levels in the eastern mango enclave. 79 

5.7 Evaluation of different management methods against the MSW. 80 

5.8 Non-destruction detection of mango stone weevil.  82 

 CHAPTER SIX 84 

6.0 Conclusion and recommendation 84 

6.1 Conclusion  84 

6.2 Recommendation  86 

 References  87 

 Appendix  97 

 

 

 

 

 

 

 

 

 

 

 

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LIST OF TABLES 

Number Title of table Page 

2.1 Top ten mango-producing countries 18 

2.2 Nutrient component of 165g of sliced mango 22 

3.1 List of communities captured during the survey   43 

4.1 Number of years in farming 50 

4.2  Pest encountered 54 

4.3 Control measures employed against MSW 55 

4.4  Annual income from fruit sales 61 

4.5  Annual expenditure on pest control 61 

4.6 Annual expenditure on mango stone weevil control 62 

4.7 Mango stone weevil infestation levels within the eastern mango enclave 63 

   

   

   

 

 

 

 

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LIST OF FIGURES 

Number Figure Page 

2.1 Haden 13 

2.2 Keitt 14 

2.3 Kent 15 

2.4 Palmer 16 

2.5 Tommy Atkins 17 

2.6 Egg-laying mark of mango stone weevil 29 

2.7 A larva of mango stone weevil  29 

2.8 Pupa of mango stone weevil 29 

2.9 Adult mango stone weevil 29 

2.10 Geographical distribution of MSW in Africa 30 

3.1 Map of the study area 41 

3.2 A mango tree with a sticky band 45 

3.3 The trunk of a mango tree treated with chlorpyrifos 46 

3.4 The trunk of a mango tree treated with grease 47 

4.1 Age of respondents 49 

4.2 Farm size of respondents 51 

4.3 Varieties of mango cultivated by respondents 52 

4.4 Number of varieties cultivated by respondents 53 

4.5 Time farmers usually control MSW 56 

4.6 The developmental stage of mango fruit at which MSW usually attacks 57 

4.7 Status of the mango stone weevil as a major pest of mango 58 

4.8 Season and infestation levels 59 

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4.9 The targeted consumers 60 

4.10 Average level of infestation of MSW for minor and major season  65 

4.11 Total number of infested fruits during the major and minor season 66 

4.12 The X-ray image of an uninfected mango fruit  67 

4.13 The X-ray image of infected mango fruit with a damaged seed and a spongy 

tissue  

68 

 

 

 

 

 

 

 

 

 

 

 

 

 

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List of Appendices 

Appendix  Title of appendix Page  

1 Results of analysis from the questionnaire using SPSS 98 

2 Chai-Square analysis of selected parameters to determine the 

association between selected parameters. 

107 

3 ANOVA for the total number of infested mango fruits over the 

growing period for the major season  

112 

4 ANOVA for the total number of infested mango fruits over the 

growing period for the minor season 

114 

5 Questionnaire for mango farmers 117 

 

 

 

 

 

 

 

 

 

 

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LIST OF ABBREVIATIONS 

ACP-EU Africa, Caribbean and Pacific – European Union 

ANOVA  Analysis of Variance 

CABI  Centre for Agriculture and Bioscience International 

CCALS Cornell College of Agriculture and Life Science 

CORAF Central African Council for Agricultural Research and Development  

CRFG  California Rare Fruit Growers  

DAF Department of Agriculture and Fisheries  

EFSA European Food Safety Authority  

EPPO European and Mediterranean Plant Protection Organisation  

EU European Union 

FAO Food and Agricultural Organisation 

GDP Gross Domestic Product 

GEPA Ghana Export Promotion Authority  

GNA Ghana News Agency 

MOAP Market Oriented Agriculture Programme 

MoFA Ministry of Food and Agriculture 

MSW Mango Stone Weevil 

PVC Polyvinyl Chloride 

RDI Reference Daily Intake 

SPSS Statistical Package for the Social Science 

USAID United States Agency for International Development 

YKMFA Yilo Krobo Mango Farmers Association  

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CHAPTER ONE 

1.0 INTRODUCTION 

Mango (Mangifera indica L.), is an important tree crop which is cultivated throughout the 

tropical and semi-tropical regions of the world. Mango also referred to as the “King of fruits” 

is a drupe or a stone fruit containing a large seed in the middle. According to Raman (2018), 

the fruit is a good source of dietary fibre, and vitamins and has antioxidant properties. Sambrani 

et al., (2015), also stated that the mango fruit is very nutritious and rich in carotenes.  

The crop is cultivated in about ninety (90) countries worldwide with about 50.65 million metric 

tonnes produced in 2017 (Pariona, 2018). India accounts for approximately 38.5% as the 

leading producer of mango, followed by China and Thailand on the world table accounting for 

9.5% and 7.5% respectively (FAO, 2019). It is estimated that the continent of Asia produces 

about 56.5% of the world’s mango while Africa supplies only 10%. 

Egypt is the largest mango-producing country in Africa followed by Nigeria and Sudan ranked 

eighth, tenth and twelfth in the world respectively (Pariona, 2018). West Africa produces about 

one point five (1.5) million metric tonnes of mangoes annually representing about four percent 

(4%) of the global production (CORAF, 2019). 

Commercial cultivation of grafted mango varieties has been increasingly adopted by Ghanaian 

farmers since the late 1990s, mainly due to programmes on food security sponsored by the 

United States Agency for International Development (USAID) and efforts of the Ministry of 

Food and Agriculture (MOFA) (Van Melles and Buschmann, 2013). 

Mango cultivation in Ghana occurs in two (2) zones namely, the southern and northern zones. 

The northern zone is composed of Upper East, Upper West, Northern, Brong Ahafo and 

Ashanti regions while the Central, Eastern, Greater Accra and Volta forms the southern zone 

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(Abu et al., 2011). This vast land area provides a great window for an increase in mango 

production.  

The fresh fruit export market in Ghana is a profitable business, earning the nation millions of 

dollars in foreign exchange (Akotsen-Mensah et al., 2017; Abdulahi et al., 2011). It is projected 

that Ghana has more than 12,000 ha of land under mango cultivation and most of the fruits 

produced are exported to Europe and the Middle East. According to the Ghana Export 

Promotion Authority’s report on potential markets of mango (2017), Ghana was the third-

largest supplier to the United Kingdom in 2016, after Brazil and Peru. The growing interest in 

the export of fresh mango has therefore made mango production one of the fast-developing 

sectors of Ghana’s agriculture and it has been the strategy of the government to make mango 

the leading non-traditional cash crop expected to contribute to the highest foreign exchange for 

the country thus exceeding cocoa (GEPA, 2009). Abu et al., (2011) equally, stated that the crop 

has great potential to become a major foreign exchange earner. In terms of export earnings, the 

current yield per acre of cocoa stood over GH¢1000; citrus was GH¢1500 – 2500 but mango 

ranged between GH¢2500 – 4000 (Zakari, 2012).  

The government of Ghana and the private sector have realised this comparative advantage and 

are doing everything to promote mango production to meet the high export and local market 

demands for fresh fruits, and processed products including mango jams, dried fruits, flavours 

and juice. Mango is seen as one of the finest fruits and an important tree crop in tropical and 

subtropical regions of the world (Krishnan, et al., 2009). Van Melle and Buschmann (2013), in 

their research on the comparative analysis of the mango value chain models in Benin, Burkina 

Faso and Ghana, stated that Ghana has a comparative advantage over her next-door countries 

largely because it has double harvesting seasons in the south (i.e., major and minor). 

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Mango cultivation is one of the paramount farming activities in the Yilo Krobo Municipality 

of Ghana. Following the economic prospects and potentials presented by the cultivation of the 

crop, there have been both private and public sector interventions to enable the country to 

obtain optimum benefits from mango production. In Ghana, the Yilo Krobo Municipality is the 

only area in the country credited with a bimodal production system (MoFA, 2013) and almost 

forms the entire coastal savanna zone. 

Crop production in the tropics is however stifled by several factors such as high cost of inputs 

including fertilizers, poor quality of planting materials, insufficient and expensive labour costs 

for harvesting and other farming practices, post-harvest losses due to poor handling and 

marketing channels, inadequate processing machinery, pests and diseases infestation, etc. and 

mango cultivation is not an exception. Okorley et al., (2014) also established that pests and 

diseases, as well as the unstable market price of fresh fruit and inadequate funding were some 

of the major problems confronting most mango farmers in the Dangme West District of Ghana., 

Abu et al. (2011), in addition, said a substantial waste of fruits during harvesting, especially of 

exotic mango types, is a key constraint in mango production. With the above-listed constraints, 

the most devastating is the damages caused by pests and diseases. This is because if insect pests 

and diseases are not controlled, they can destroy an entire mango plantation, leaving the farmer 

with no income. (Akotsen-Mensah et al., 2017).  

Every crop plant has a good number of insect pests attack during its lifecycle and the mango 

tree is not exempted. Fruit flies, mango mealy bugs, thrips, aphids, scale insects, tree borers, 

mango stone weevils and mango hoppers are a few examples. However, the key pests of mango 

include the fruit flies, mango stone weevil, tree borers and mango hopper (Obeng-Ofori, 2007; 

Pena and Mohyuddin, 2000).  

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The mango stone weevil also known as the seed weevil is a monophagous insect pest of mango. 

According to CABI (2015), the complete development of mango stone weevil is only achieved 

on mangoes. It is a major problem in mango production all over the world. It occurs in India, 

throughout south-east Asia, parts of Australia, Africa, and the Americas.  

Follett (2002) and Verghese et al., (2005) stated that, controlling the mango stone weevil is 

important because it can increase fruit drops during early fruit development and may reduce 

germination capability of seeds. Peng and Christian (2007) also reported that the control of 

mango stone weevil is of great importance because adult oviposition activities lead to 

downgrading of fruit and as a result, the grower’s profit decreases.        

 

1.1 Problem Statement 

The mango stone weevil (Sternochetus mangiferae F.) is a key and an important quarantine 

pest for commercial mango production. Because of its quarantine status, some large mango 

importing countries, including the United States, China, Japan, the European Union, and certain 

countries in the Arabian Gulf, place quarantine restrictions on mangoes imported from affected 

areas. (Peng and Christain, 2007). 

According to CORAF (2019), the economies of mango-producing countries in West Africa 

(where Ghana is geographically located) and exporters have experienced substantial losses 

because of interceptions of mango export.     

Furthermore, most mango pests and diseases are of worldwide quarantine concern, and their 

presence in the production chain is enough to cause mangoes to be rejected on the export market 

(Clarke et. al., 2005). There has been a threat of banning mangoes from Ghana by importing 

countries such as the United State of America and the European Union since 2012, due to the 

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incidence of pests. When the United States banned the export of fruit from Ghana in 2013, the 

horticultural industry suffered a loss of over $10 million. (GEPA, 2014).      

According to Quartey (2008), Ghana's comparative advantage in the production of fresh 

mangoes, particularly the grafted variety, has the potential to drastically turn around and 

transform the economy if more attention is redirected and focused on mass cultivation of the 

fruit.  This enormous potential has yet to be realized and it is largely because of the mango 

stone weevil's presence in Ghana. There is a low motivation for farmers to control the mango 

stone weevil, since the fruit’s eating quality is unaffected (CABI and EPPO, 2015).  

The easy detection of the pest without destroying the fruit is also another headache, since 

infested fruits cannot be practically distinguished from uninfected fruits unless they are cut 

open because infested fruits are often not visibly damaged (Woodruff and Fasulo, 2006). There 

is a risk of the nation being banned because of infestation which cannot be easily detected.    

Farmers have been using insecticides to control the mango stone weevil, but the problem 

persists. This is partially due to the high cost of inputs and the difficulty of obtaining them 

(Micah and Inkoom, 2016). The insecticides also have the disadvantage of killing beneficial 

insects which helps in pollinating flowers leading to fruit sets since most of them are broad-

spectrum insecticides. Some insecticides are very effective in controlling the mango stone 

weevils but affect the quality of fruits due to the residual effects. Farmers do not also apply the 

insecticides at the right time. Time of application is very critical in the control of insect pests. 

The main approach in using these chemicals is to employ trunk application and foliar spray at 

the period of oviposition to target diapausing adults (EFSA, 2018).  

Good farm sanitation is another efficient method of reducing adult population. During and 

immediately after harvesting, all fallen fruit and fruits with seed damage must be destroyed 

(Peng and Christian, 2004). Although this cultural method is effective, it is practically difficult 

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to carry out on large plantations since this practice cannot be mechanised and should be done 

manually. 

The weaver ant (Oecophylla smaragdina) is reported to be the mango stone weevil's most 

efficient biocontrol agent (Peng and Christian, 2005). However, the mass rearing and release 

of the weaver ant requires much time and resources. The entomopathogenic fungus 

(specifically Beauveria bassiana) is also reported to control the mango stone weevil (Peng and 

Christian, 2007). 

Physical barriers such as the sticky band and grease have also produced good results (Muriuki 

et al., 2011). These are applied at the ends of tree trunks just at the time of flowering to prevent 

migrating of weevils to branches for egg-laying. 

Although researchers have conducted numerous investigations into the control and 

management of the mango stone weevil (Sternochetus mangiferae), the pest persists in the 

country (EFSA, 2018). Farmers and exporters therefore, have challenges in exporting their 

mango fruits due to quarantine restriction of which the mango stone weevil infestation is a 

factor (Zakari, 2012).   

 

 

1.2 Justification 

Crop production in Ghana is faced with numerous problems and mango production is not 

an exception. Amongst the problems confronting agriculture in Ghana is pest management 

which has tremendous impact on crop yield due the militating effect of crop pest.  

Identification and implementation of measures to eliminate the bottlenecks in mango 

production would open a new window to foster rapid growth and development of the 

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agricultural sector. The cultivation of mango offers employment to people, generates 

income for the farmer and has the potential to generate extra foreign exchange for the nation 

(MoFA, 1998) 

To propel agriculture to play its role in economic development especially in developing 

countries such as Ghana, studies must be carried out to find out some of the major 

constraints limiting growth in the agricultural sector and how to curtail them.  

This research aims at finding the most effective management measures for controlling the 

mango stone weevil within the eastern mango enclave. The outcome of this work would 

provide an idea of the infestation levels of the mango stone weevil and the right measures 

to adopt in the management of the MWS to help bring the MWS attacks to tolerable levels 

to ensure the availability of high-quality mango fruits for both the local and international 

market.   

 

 

 

 

 

 

 

 

 

 

 

 

 

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1.3 General Objective 

The study aims at reducing infestation and phytosanitary risk resulting from mango stone 

weevil (Sternochetus mangiferae F.) infestation. 

1.4. Specific Objectives 

▪ To assess the knowledge, attitude and practice of mango farmers towards the mango 

stone weevil. 

▪ To determine the levels of mango stone weevil infestation and distribution in the eastern 

mango enclave of Ghana. 

▪ To investigate the effect of insecticide application and trunk banding on infestation of 

mango stone weevil.  

▪ Assessment of mango stone weevil in harvested fruits using soft X-ray technique. 

 

 

 

 

 

 

 

 

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CHAPTER TWO 

2.0 LITERATURE REVIEW 

2.1 The mango crop  

Mango (Mangifera indica L.) is a tree crop thought to have originated in Southeast Asia and 

over thousand (1000) varieties have been discovered around the world (Rymbai et al., 2014). 

Yadav and Singh (2017), also stated in their work on the origin and distribution of mango that, 

mango originated from the Southern Asia's foothills of the Himalayas (eastern India, Burma, 

and the Andaman Islands) surrounding the Bay of Bengal, where it still grows wild in the hills 

of Assam and surrounding regions, dating back to 4000 BC. 

According to Singh et al., (2016), an extensive comparison of the anatomy and morphology of 

several modern-day species of the genus Mangifera with fossil samples supported the view that 

the mango genus originates from North-East India, where it spread into surrounding areas of 

South-East Asia. Today, the genus Mangifera has 72 species, the majority of which may be 

found in the rain forests of Malaysia and Indonesia.  

Mehta (2017) also added that scientific evidence suggests that the mango first appeared 25 to 

30 million years ago in North-East India, Myanmar, and Bangladesh, from which it spread 

south to Southern India. Wild mango species are also found in India, Sri Lanka, Bangladesh, 

Myanmar, Thailand, Kampuchea, Vietnam, Laos, Southern China, Singapore, Brunei, the 

Philippines, Papua New Guinea and the Solomon and Caroline Islands (Kole, 2011; Litz, 

2009).  

Mango seeds were imported into America from the West Indies, India and Cuba during the 

second half of the 19th century. In the 1830s, cultivars arrived in Florida. Most of the famous 

mango types grown throughout the world today are derived from the Florida mango (Yadav 

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and Singh, 2017). Presently mango is said to be one of the most adaptable and widely grown 

fruit crops of tropical and subtropical regions (Vasugi et al., 2012; Neguse et al., 2019).  

2.1.1 Botany 

The crop belongs to the family Anacardiaceae (the cashew family), order Sapindales, class 

Magnoliopside and the division Tracheophyta (the vascular plants) (Singh et al., 2016). Mango 

is a delicious stone fruit (drupe) produced by a variety of tropical tree species that belong to 

the flowering plant genus Mangifera, cultivated primarily for its edible fruit.  

Mango trees reach a height of 35–40 meters and have a crown radius of about 10 meters. The 

trees have a lengthy lifespan, with some specimens still bearing fruit after 300 years (CRFG, 

2015). It has a taproot which could descend to a depth of about 6m. The leaves are evergreen, 

alternating and simple. Young leaves are orange-pink, but as they grow, they turn a dark, glossy 

red and finally dark green. 

Flowers are generated toward the end of panicles of about 1040cm long; each flower is small 

and white with five petals of about 5–10mm long, with a mild and sweet fragrance (Morton, 

1987). There are over five hundred (500) known varieties of mangoes, many of which ripen in 

summer, while some produce a double harvest (Toptropicals, 2014). The fruit takes about four 

to five months from blossoming to ripening. 

The size, shape, colour, sweetness, and eating quality of ripened mango fruits varies depending 

on the cultivar. Fruits might be yellow, orange, red, or green, depending on the cultivar. The 

fruit has a single flat, oblong pit on the surface that might be fibrous or hairy and does not 

easily detach from the pulp. The fruits can be round, oval, or kidney-shaped, with lengths 

varying from 5–25 cm and weights ranging from 140 grams to 2 kilograms per fruit.  When 

fully ripe, the skin is leather-like, waxy, silky, and aromatic, ranging in colour from green to 

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https://en.wikipedia.org/wiki/Taproot
https://en.wikipedia.org/wiki/Panicle


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yellow, yellow-orange, yellow-red, or flushed with various shades of red, purple, pink, or 

yellow. (Morton, 1987).  

Morton (1987) further stated that, mangoes have a particular aromatic and sweet scent. A thin 

coating of 1–2 mm thick covers a solitary seed 4–7 cm long inside the pit.  Mango has a tough 

seed that does not like to be frozen or dried (Marcos-Filho, 2014). Mango trees are easy to 

establish from seed, with good germination success when received from mature mangoes.  

2.2 Mango varieties 

Rymbai et al. (2014), in their research stated that, there are over thousand varieties of mangoes 

identified around the world. Seedling populations and grafted variations are both available. In 

certain cases, the same mango variety is given several names depending on where it is grown. 

(Ravishanker and Misra, 2010). Although there are hundreds of mango varieties being 

cultivated around the world, the varieties of mango currently grown in Ghana include Keitt, 

Kent, Haden, Palmer, Eldon, Tommy Atkins, Zill, Amelie (Amini), Irwin, Julie (Saint Julian), 

Jaffna, Njala 5, Springfels (Springfield) and Sunset (Abu et.al., 2011).  

Akotsen-Mensah et al., (2017), in their work on pest management knowledge and practices of 

mango farmers in southeastern Ghana, said the mango types that are commonly produced in 

the study area covering Yilo Krobo (Somanya), Manya Krobo (Kpong), and Shai Osudoku 

(Ayikuma) included Keitt, Kent, Palmer, and Haden.  

Agyapong (2013) stated that, the common varieties of mango were Keitt, Kent, Palmer, Erwing 

(Irwin) and Haden. Frimpong (2013), also articulated that, mango varieties cultivated in Ghana 

are Keitt, Kent, Francine, Tommy Atkins, Palmer, Haden and Irvin (Irwin). 

Okorley et al. (2012), reported that about 68.9% of farmers grow two or more varieties with 

Kent, Keitt and Palmer as the most popular varieties in descending order. Zakari (2012), in his 

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work titled “National Mango Survey”, stated that, Ghana grows a variety of mangoes, however 

Keitt is the most common (approximately 80%), Kent (10%) and other fourteen varieties 

(Palmer, Tommy Atkins, Zill, etc.) recording very little quantities. Akurugu (2011), on the 

contrary stated that, the most popular variety is Kent (32.89%), Amelie (29.53%), Keitt 

(28.19%) and others sharing a smaller percentage of (9.39%). Fordjour (2014) also stated that, 

Ghanaian farmers grow Keitt 48%, Kent 25.6%, Palmer 10.4%, Haden 6.4% and the others 

totalling about 9.4%. 

This puts Keitt, Kent, Palmer, Irwin (Irvin or Erwing), Haden and Tommy Atkins as the 

common varieties. Because of their low fibre content and high demand in international markets, 

Kent and Keitt mangoes have received a lot of attention among the Ghanaian mango varieties. 

(Amos, 2014).   

 

2.2.1 Haden  

The Haden mango variety is a mid-season crop that originated from Florida, United States. The 

fruit is ovate-shaped with a rounded apex (Fruitrop.com, 2019). The skin is golden-yellow and 

crimson red blush when matured and can weigh about 350-650g. It has medium to low fibre 

with a rich and sweet, slightly turpentine flavour near the skin. It is monoembryonic (DAF, 

2014).      

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Figure 2.1: Fruit of the Haden variety of mango.  

Source: https://en.wikipedia.org/wiki/File:Haden_mango.jpg 

  

2.2.2 Keitt   

Keitt is a mango cultivar that blooms late in the season known to be a progeny of Brooks and 

originates from South Florida. The fruit is relatively large, with some reaching over 500g in 

weight. They have a rounded apex and no beak. The skin is usually green with a little red blush. 

It is fibreless, acidic and sweet, and a monoembryonic seed characterize the meat. It is one of 

the highly prized late-season types due to its high disease resistance (Campbell, 1992). 

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Figure 2.2: Fruit of the Keitt variety of mango.  

Source: https://en.wikipedia.org/wiki/File:Mango_KEITT_Asit.jpg 

2.2.3 Kent  

Kent originates from Florida and is believed to be an offspring between Brooks and Haden 

Campbell, 1992). The fruit is oval, measures 570–740g, and has a sweet, rich flavour. As it 

matures, it normally turns greenish-yellow colour with a red flush. The seed is monoembryonic, 

and if left on the tree for too long, it will sprout in the fruit. 

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Figure 2.3: Fruit of the Kent variety of mango. 

Source: https://en.wikipedia.org/wiki/File:Mango_Kent_Asit_fs8.jpg 

 

2.2.4 Palmer 

The palmer variety of mango which is believed to be a progeny of Haden and originates from 

Florida.  The fruit is huge, with some weighing over 600 grams. When ripe, the fruit is yellow 

with a crimson blush; nevertheless, the fruit becomes purple long before it fully matures. The 

flesh is orange-yellow in colour and has a moderate, aromatic flavour. It has a monoembryonic 

seed and is low in fibre. It is a late-season cultivar. It is a late-season cultivar (Campbell, 1992).  

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Figure 2.4: Fruit of the Palmer variety of mango. 

Source: https://en.wikipedia.org/wiki/File:Mango_Palmer_Asit_fs8.jpg 

  

  

2.2.5 Tommy Atkins  

The Tommy Atkins variety of mango is a seedling of Haden. fruits are a medium to large sized 

mango variety with an oval or oblong shape, averagely weighing up to 450-710g (CRFG, 

2015). The skin has a dark red blush with green and yellow highlights that covers much of the 

fruit and its thick. This variety is valued for its long shelf life and resistance to bruising and 

deterioration during handling and shipping.  

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Figure 2.5: Fruit of the Tommy Atkins variety of mango. 

Source: https://en.wikipedia.org/wiki/File:Mango_TommyAtkins03_Asit.jpg 

 

2.3 Mango production in the world 

Mango is cultivated on approximately 3.7 million hectares worldwide and places second out 

of the tropical fruit crops (Jahurul et al., 2015). Despite being classified as a tropical crop, 

mangos are increasingly grown in subtropical climates in eighty-nine nations of the world. The 

major mango growing countries are India, Pakistan, Bangladesh, Myanmar, Sri Lanka, Florida 

and Hawaii of USA, Australia, Brazil, Thailand, the Philippines, Malaysia, Vietnam, 

Indonesia, Fiji Islands, Egypt, Israel, South Africa, Sudan, Somalia, Kenya, Uganda, Tanzania, 

Niger, Nigeria, D. R. Congo, West Indies Islands, Cambodia, etc. (Yadav and Singh, 2017). 

According to the FAO (2019), estimated that, the global production volume of mango was 

about 48.36 million metric tonnes in 2017. Asian countries accounted for about 74.69%, Africa 

14.9% and the rest of the world produced about 10.41%. Below is a table showing the world's 

top ten mango producers with their respective output for the year 2017.   

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Table 2.1. Top ten mango producing countries in the world for year 2017. 

Rank Country Production (Tonnes) Percentage (%) 

1 India 19,686,900 51.51 

2 China  4,870,100 12.74 

3 Thailand  3,838,600 10.04 

4 Indonesia  2,239,300 5.86 

5 Mexico 1,581,700 4.14 

6 Pakistan  1,525,200 3.99 

7 Egypt  1,397,000 3.65 

8 Bangladesh  1,155,600 3.02 

9 Kenya 1,024,500 2.68 

10 Brazil  904,100 2.37 

TOTAL  38,223,000 100 

Source: FAO (2019). Major tropical fruits - Statistical compendium 2017. 

 

2.3.1 Mango production and distribution in Ghana 

According to Yadav and Singh (2017), Portuguese traders brought mango to West Africa in 

the 17th century. Abu et al., (2011), also argued that Ghanaian farmers have been cultivating 

mangoes since the 1920’s. In Ghana, mango is produced in large quantities in Somanya in the 

Yilo Krobo District of Eastern Region. Because there is a guaranteed dual harvest in a year, 

both during the major and minor season. 

In 2016, Ghana was said to have exported about 476,200 metric tonnes of mangoes (GEPA, 

2017), which was about 16.78% higher than mango exports made in the year 2015. The main 

destination of mango produced in Ghana is the European market with the United Kingdom 

importing about 57.2% of Ghana’s export according to GEPA (2017). Ghana can compete in 

the European markets with the Latin American suppliers since there is a guaranteed dual 

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harvest in a year (Frimpong, 2013). The country’s location geographically, gives her a greater 

advantage as its closer to Europe and the Middle East. However, exports to the Middle East 

countries such as Lebanon is dominated by Egypt (GEPA, 2017). 

Grumiller et al. (2018), stated that, Ghana is battling to improve fresh produce exports but is 

specialized in the processed mangoes (mainly fresh sliced and dried fruits). Mango production 

is currently around 110,000 tonnes, accounting for 0.3 percent of agricultural GDP. With over 

30% post-harvest losses (MOAP, 2016), the volumes accessible for processing are around 

30,000 tonnes, whereas 40,000 tonnes are typically eaten locally as fresh fruits.  In West Africa, 

Ghana is second to Burkina Faso, producing about 800-1,000 tonnes of dried mango for 

exports, whiles the latter exports about 2,000 tonnes per year Grumiller et al. (2018). 

The Ghana News Agency (GNA, 2017) stated that, about 2,218 metric tonnes of fresh cut and 

dried mangoes were exported in 2015 to countries in Europe, South Africa, Israel, USA, China, 

Russia and Niger. The institution also revealed that, about seventy percent (70%) of all 

mangoes produced in the country is traded on the local market as fresh or processed, while 432 

metric tonnes were imported to feed some local processing industries mainly in the off season, 

as well as 479 metric tonnes of mango juice were also imported.  

Abu et al. (2011), stated that, mango producing areas in Ghana has been put into two zones, 

the Southern comprising parts of Central, Eastern, Greater Accra, and Volta Regions (now Oti 

and Volta regions) and the Northern zone made up of Ashanti, Brong Ahafo (now Bono East, 

Ahafo and Bono regions), Upper East, Northern (now Northeast, Northern and Savannah) and 

Upper West Regions. The Western Region (now Western and Western North Region) was the 

only region where mangoes are not commercially cultivated. The southern zone enjoys two 

seasons mainly because of the bimodal rainfall pattern whiles the Northern zone has one mango 

season presumably due to the unimodal raining season in the guinea savannah zone.  

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Ghana, according to agronomists, has a superior comparative advantage in Africa in terms of 

rainfall, soil, and proximity, and might become a major producer in a few years if the country 

invests in the sector (Quartey, 2008).          

2.4 Economic importance of mango 

Mango has numerous uses and due to that it has been given different names such as “Golden 

Tree”, “Next Cash Crop”, “Gold Mine”, “Ghana’s Future”, etc., (Avah, 2008). The mango fruit 

is used at all the stages of its development be it mature or not. Chutney, pickles, and juice are 

all made using the raw fruit. Aside being used as a desert, the ripe fruit is also used in preparing 

products such as squash, syrups, nectars, jam and jellies. The kernel also has 8-9 percent high-

quality fat that can be utilized to make soap as well as a substitute for cocoa butter in 

confectionary (Agricoop.gov).     

According to Timesofindia.com (2017), quercetin, fisetin, isoquercitrin, astragalin, gallic acid, 

and methyl gallate are antioxidants found in mangoes. Breast cancer, colon cancer, prostate 

cancer, and leukaemia are all prevented by above mentioned antioxidants found in mango. 

Mangoes are also abundant in vitamin C, fibre, and pectin, making them an excellent fruit for 

lowering cholesterol. 

Mangoes are known to cleanse the skin from deep within the body when consumed. Mango 

leaves can equally be boiled or soaked overnight to treat diabetic patients. In addition, since 

mango has a low glycemic index, it will not raise blood sugar levels if consumed in moderation 

(Raman, 2018).  

Mangoes are high in tartaric and malic acids, as well as traces of citric acid, which assist the 

body maintain its alkali reserve. The fruit is high in fibre which aids in normal digestion, 

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preventing many stomach-related ailments, and burning unneeded calories from the body, 

assisting in weight loss. (Timesofindia, 2017).   

The mango, often known as the 'king of fruits' and the 'love fruit,' has aphrodisiac properties 

that boost libido and stamina. The mango tree is regarded as a symbol of love, and people 

believe that it could grant desires. (Yadav and Singh, 2017). 

The abundance of vitamin A in mangoes, makes t is an excellent fruit for improving vision. 

Mangoes also contain vitamins C and A, as well as a variety of carotenoids, all of which are 

vital and advantageous to maintaining a robust and healthy immune system (Raman, 2018). 

Individuals with difficulties in concentration and low memory, could gorge on mangoes. The 

high iron content in mango is a natural remedy for anaemic people (Timesofindia.com, 2017). 

Mangoes are not only delicious, but they also have a high nutritional value. According to Raman 

(2018), one cup (165g) of sliced mango provides the following nutrients as shown in the table 

2.2. on page 22. 

The mango tree aside providing us numerous nutritional benefits, is a major foreign exchange 

earner for the nation. According to SelinaWamucii.com, before 2019, a kilogram of mango was 

sold for US$6.34 in 2017, US$6.59 in 2018 and increased to US$7.26 in 2019. The total values 

in export for mangoes in Ghana were US$2,223,000, US$59,326,000, US$68,149,000 and 

US$68,322,000 for the years 2016, 2017, 2018 and 2019 respectively (Selinawamucii.com).   

 

 

 

 

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Table 2.2: Nutrient component of 165g of sliced mangoes 

 

Nutrient Component in grams (g) Component in percentage (%) 

Calories 99  

Proteins 1.4  

Carbohydrate  24.7  

Fat  0.6  

Dietary fibre 2.6  

Vitamin C  67% of reference daily intake 

(RDI) 

Copper 

 

 20 RDI 

Folate   18 RDI 

Vitamin B6  11.6 RDI 

Vitamin A  10 RDI 

Vitamin E  9.7 RDI 

Vitamin B5  6.5 RDI 

Vitamin K  6 RDI 

Niacin   7 RDI 

Potassium   6 RDI 

Riboflavin   5 RDI 

Manganese   4.5 RDI 

Thiamine   4 RDI 

Magnesium   4 RDI 

Source: https://www.healthline.com/nutrition/mango#nutrition 

 

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2.5. Constrains to mango production 

The cultivation and management of mango just as any other crop is bedevilled with several 

constrains or challenges. According to Micah and Inkoom (2016), production constraints are 

factors that limit farmer’s ability to achieve their production objective as best as possible 

Shinde and Sawant (2006), stated in their work that, the major constraints in mango production 

at Maharashtra in India were unavailability of inputs, quality of mango grafts, lack of 

knowledge regarding improved technology, poor rates offered by middlemen and lack of 

knowledge in exporting of fruits. 

Micah and Inkoom (2016), in a research survey also stated that, the constraints faced by mango 

farmers in the Yilo Krobo Municipality included accessibility and high cost of inputs, access 

to credits and unavailability of skilled labour. Access to transportation systems, fluctuating 

market price for mango fruits, and access to export market were also captured as challenges. 

They further indicated that, land tenure systems, and access to government support are some 

of the factors limiting the production potentials of farmers. Pest and disease control, effective 

pruning, harvesting, and fruit drops were cited as some of the production activity related 

constraints limiting mango productivity in the Municipality.  

According to Van Melle & Buschmann (2013), the major constraints facing mango farmers 

included quality issues, poor negotiation power, high transaction cost and lack of irrigation 

infrastructures. Okorley et al, (2014) added that, most mango producers in Ghana's Dangme 

West District faced a variety of challenges, including fluctuating market prices for fresh fruit, 

pests and diseases, and a lack of cash. In 2015, Abdul-Razak et al, also conducted a research 

in the Savelugu/Nanton Municipality in the Northern Region of Ghana and stated that, disease 

and pest attacks, low yields, bushfire outbreaks, lack of cash credit, inadequate inputs, lack of 

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irrigation, no flexible contract terms and delayed payment were the significant obstacles facing 

mango farmers.  

In addition, Abu et al, (2011) wrote that, the substantial waste of fruits during harvesting, 

particularly of exotic mango types, is a key restriction in mango production. Akurugu (2011), 

stated that, a substantial portion of mangoes harvested are wasted annually due to improper 

harvesting and post-harvest practices, diseases and lack of facility and technology to extend 

the storage life.  

Agyapong (2013), disclosed that, harvesting labour is insufficient and untrained, heavy 

occurrence of diseases and pest, lack of cold storage facilities, mechanical accidents because 

of improper handling, a weak road network, insufficient transportation, and poor packing and 

fewer number of processing plants as the major problems faced by handlers of mango fruits.  

Micah and Inkoom (2016), also added that, productivity of farmers depends on several factors, 

such as quality of previous crop, weather and soil conditions, altitude, control of pest and 

diseases, fertilizer application and cultivar.  

The common factor in most of the research findings relating to challenges or production 

constrains were pest and diseases, inadequate credit facilities, lack of technology to extend 

shelf-life and lack of irrigation.  For the mango sector to explore its full potential as the nation’s 

next “cash crop”, Ghana’s future or “gold mine”, these constraints which serves as hindrances 

must be curtailed. 

2.5.1 Pest and diseases 

According to Ravishankar and Misra (2010), over 492 insect species attack mangoes around 

the world. Out of this number, 298 species of insects and mites both significant and minor, 

have been identified: fruit feeder (87), foliage feeder (127) and feeds on inflorescence (26), 

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buds (33) and branches and trunk (25). In badly infested orchards, they inflict a 20 to 100 

percent loss. Although mango is plagued by several insect pests, a few are particularly 

damaging to the industry and are responsible for significant losses in Ghanaian mango 

production. 

Fruit flies, mango stone weevils, tree borers, and mango hoppers are the most common pests 

on mango trees. (Pena and Mohiuddin, 1997). Reddy et al. (2018), also stated that, over 400 

insects and mites, are noted as pest of mangoes but, only a few are of economic importance. 

Out of the few insects of economic importance, fruit flies and the stone weevils are of 

quarantine importance and restrict international trade of mangoes (Reddy et al., 2018).       

Currently, the world's focus is on producing high-quality fruit for both domestic and 

international markets therefore, Insects that contaminate fruits by eating, scratching, or 

ovipositing in the pulp or seed can result in appreciable losses. (Aluja, 1994; Obeng-Ofori, 

2007).  

At every stage of its existence, mangoes suffer from a variety of diseases. Some of these 

diseases are economically significant because they cause significant losses in mango output. 

Reddy et al., (2018), further stated that, the major mango diseases of economic importance 

include powdery mildew, anthracnose, gummosis, dieback, sooty mould, stem end rot, scab 

and damping off.    

Hoque (1985), also stated that, there are many diseases of mango caused by fungi, bacteria 

viruses, phanerogamic parasites and nutritional deficiencies, however, number and severity of 

diseases vary as to cultivars. The major diseases are mango malformation, anthracnose, 

bacterial leaf spot, scab, fruit rot, sooty-mould black mildew, collar rot, brown felt, thread 

blight, pink disease, shoestring root, leaf spots, blight, powdery mildew, and red rust. Stem end 

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rot, black mould rot, soft rots, alternaria rot, dry rot, black spot, brown spot, phomispsis rot, 

bacterial soft rot and bacterial rot were also listed by Hoque (1985), as major diseases.    

2.6 The mango stone weevil 

2.6.1 Biology and ecology of the mango stone weevil 

Adult mango stone weevils during March and April, eat mango leaves and delicate shoots. 

(Subramanyam, 1926; CABI and EPPO, 2015). They are nocturnal, readily fly, generally feed 

from late afternoon until dusk, mate and oviposit. Adults experience a diapause after 

emergence, which varies in length depending on the geographic range. Adults emerging in June 

in southern India and Hawaii, for example, enter a diapause from July until late February the 

following year (Shukla and Tandon, 1985; CABI and EPPO, 2015).  

The mango stone weevils can withstand long and unfavourable conditions. During the non-

fruiting period, weevils hibernate in crevices near mango trees or under loose bark on trunks 

and branch terminals. Only a few adults experience two seasons, with a diapause interval in 

between (Peng and Christian, 2004; CABI and EPPO, 2015). 

Shukla and Tandon (1985), revealed that, females oviposit 3-4 days after mating. This occurs 

around mid-March and in the first week of April, it reaches its height. Peng and Christian 

(2004), also stated that, oviposition occurs around mid-August to early October in Australia 

and oviposition period varies from 3 weeks to 6 weeks. Females constantly oviposit on a variety 

of fruit sizes, ranging from marble-sized to full-sized unripe fruits. (Hansen et al., 1989; CABI 

and EPPO, 2015), and deposit eggs primarily on the fruit's sinuses, but sometimes on the stems 

(Shukla et al., 1985; Peng and Christian, 2004).  

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https://www.cabi.org/isc/datasheet/16434#C61FFDF1-231D-4E8F-AFDE-AA62A0E34BD9
https://www.cabi.org/isc/datasheet/16434#D544FB5C-CDB3-49D7-A37B-6A4684604E40
https://www.cabi.org/isc/datasheet/16434#5F18F8FD-086F-4304-9A81-9DAC18194619
https://www.cabi.org/isc/datasheet/16434#D544FB5C-CDB3-49D7-A37B-6A4684604E40
https://www.cabi.org/isc/datasheet/16434#5F18F8FD-086F-4304-9A81-9DAC18194619
https://www.cabi.org/isc/datasheet/16434#5F18F8FD-086F-4304-9A81-9DAC18194619
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The female weevil often makes a boat-shaped cavity in the skin (epicarp), deposits its’ eggs 

and covers each egg in a brown exudate with two small-angled tails on one end and cuts a 

crescent-shaped region in the fruit 0.25-0.50 mm. A sap flow is produced by the wound, which 

solidifies and coats the egg in a protective opaque layer. These oviposition marks are difficult 

to remove on the fruit packing line, resulting in fruits being devalued (Peng and Christian, 

2007). In the laboratory, one female could lay roughly 15 eggs each day, with a maximum of 

over 300 throughout a three-month period (Balock and Kozuma, 1964; CABI and EPPO, 

2015). 

Incubation of eggs varies from 5-7 days, depending on the season and temperature (Balock and 

Kozuma, 1964; CABI and EPPO, 2015). The larva tunnels through the flesh of the apple into 

the seed after hatching. The tunnel and seed entry are entirely ceiled when the fruit and seed 

mature, such that in time, unless the fruits are sliced open, it is impossible to tell the difference 

between infested and non-infested ones.  

The entire larval development, is common in the maturing seed, although it can also happen in 

the flesh on rare occasions (Follett and Gabbard, 2000). There are five or seven larval instars 

(Hansen et al., 1989). Pupation usually last about a week and mainly takes place within the 

seed. The pupal phase lasts approximately one week (Shukla and Tandon, 1985). However, 

Hansen et al. (1989) and CABI and EPPO (2015) reported that, pupae can be found from the 

end of May through the middle of July. 

Generally, an adult will mature per seed, despite the fact that there have been as many as six 

reported (Follett, 2002). They carve their way out of the naked seed, usually through a small 

circular hole in the endocarp's concave edge, 4-8 weeks after the fruit falls and decays. In the 

Northern Territory of Australia, adults were found to be in seeds for 15-40 days from October 

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https://www.cabi.org/isc/datasheet/16434#0ADEF42E-31CD-43FF-B4A3-CBD1C25F15E7
https://www.cabi.org/isc/datasheet/16434#0ADEF42E-31CD-43FF-B4A3-CBD1C25F15E7
https://www.cabi.org/isc/datasheet/16434#A610CD38-7644-4D31-800A-359E978D13B8
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to mid-November (Peng and Christian, 2004). Rather than flying, the weevils crawl out of the 

seeds and look for a hiding place. 

There are varied reports as to the time at which the stone weevil population is high. Adults of 

the next generation appear in Bangalore, South India, in June (Shukla and Tandon, 1985; CABI 

and EPPO, 2015), but in the Northern Territory of Australia, late November to December is 

the time when new generations emerge. According to Peng and Christian (2004), it takes 

between 45-58 days for an egg to develop into adult. Adults typically stay around the parent 

tree until the following fruiting season (Jarvis, 1946; CAB and EPPO, 2015) and year after 

year, significant infestations are reported in some areas, whereas low infestations are reported 

in others nearby (Hansen et al., 1989). This makes infestations localized, such that on one farm, 

the weevil may be on a section or a portion whiles the remaining section or portion would be 

free from the weevils. 

2.6.2 Taxonomy, description and distribution of the mango stone weevil 

The mango stone weevil, otherwise known as seed weevil, mango weevil and mango nut 

weevil, according to CABI and EPPO (2015), is an invasive and monophagous pest of mango 

belonging to the Kingdom: Metazoa, Phylum: Arthropoda, Class: Insecta, Order: Coleoptera, 

Family: Curculionidae, Genus: Sternochetus and Species: Sternochetus mangiferae. It was 

initially described in 1775 in the genus Curculio.  

Freshly laid, the eggs of the weevil are creamy-white and ovate in shape (Woodruff and Fasulo, 

2006). The larvae of the first instar are long, cylindrical, legless, and exceedingly slender. The 

head is black, while the body is white. The whitish and legless final instar larvae (4th or 5th 

instar) have a curled, classic curculionid shape. (Shukla and Tandon, 1985, CABI and EPPO, 

2015).  

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https://www.cabi.org/isc/datasheet/16434#D544FB5C-CDB3-49D7-A37B-6A4684604E40
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Fig. 2.6: Close-up of an egg-laying mark of      Fig. 2.7: A larva of a mango stone weevil 

mango seed weevil. 

Source: https://www.infonet-biovision.org  

When the pupae are first produced, they are whitish, but shortly before ecdysis, they turn a very 

pale red colour. The adults have a compact body with black scales that are grey or yellowish 

in colour. Adults can fly, although they are not known to be powerful flyers, and they don't 

venture far from the fruit-bearing tree (Woodruff and Fasulo, 2006). However, there have been 

reports that they can fly further than previously imagined. They act as though they are dead when 

touched or disturbed (Infornet.biovision, 2019).  

 
Fig. 2.8: Pupa of a mango seed weevil   Fig. 2.9: Adult mango seed weevil 

Source of Fig. 2.8: A picture taken from an orchard at Somanya, Ghana 

Source of Fig. 2.9: https://www.infonet-biovision.org  

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The mango stone weevil is a common pest that can be found all around the world. In Africa, 

the pest is said to be present in almost all mango growing countries. Countries that have 

reported the presence of the mango stone weevil are Central African Republic, Gabon, Ghana, 

Guinea, Kenya, Liberia, Madagascar, Malawi, Mauritius, Mozambique, Nigeria, Réunion, 

Seychelles, South Africa, Uganda, Zambia and Tanzania (EPPO, 2018). Below is the 

distribution map showing countries where the mango stone weevil persists in Africa. 

 

Fig.2.10: Geographical Distribution of the Mango stone weevil in Africa (red marked) 

Source: CABI Updated on 10 July, 2019 

 

 

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2.6.3 Importance of mango stone weevil on mango production and export in Ghana 

One of the most critical quarantine pests for commercial mango production is the mango stone 

weevil. Because the mango seed weevil is a quarantine pest, certain significant mango-

importing countries have implemented quarantine measures. USA, China, Japan and Arabian 

Gulf countries are examples of countries that have impose quarantine restrictions on the 

importation of fruits from infested areas (Peng and Christian, 2007). Braimah and van Emden 

(2010), stated that, the presence of the MSW in the mango production system is sufficient to 

justify the fruits' rejection in the export market. 

The common reasons for rejection of fresh mangoes at the factory level includes mechanical 

abrasions, spoilage from fruit fly or stone weevil infestation (idhsustainabletrade, 2019).   

According to GEPA (2019), the European Union (EU) introduced new regulations governing 

the imports of mangos. These rules were made in response to high number of interceptions of 

mango imports due to the presence of fruit fly (non-European Tephritidae) which is one of the 

quarantine pests just as the MSW.  

ACP-EU, Newsletter (2013), stated that, because of the presence of insects declared as 

quarantine pests, mangoes supplied to certain European nations were intercepted, confiscated, 

and destroyed. This resulted in great economic losses to exporters. In 2012, there were twenty-

eight (28) interceptions of mangoes from Ghana and the cost per interception was 

US$39,348:00 (ECOWAS-TEN Newsletter, 2012). EUROPHYT (2017), reported that, one 

consignment was intercepted in Europe.  

According to CABI and EPPO (2015), the greatest damage caused by MSW is to interfere with 

fruit export, because of quarantine restrictions. Mango stone weevil infestation can also 

enhance fruit drop throughout fruit development, and seed germination capacity can be 

reduced.         

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 2.6.4 Management of Mango stone weevil 

2.6.4.1 Chemical control  

According to CABI and EPPO, (2015) and Villiers (1987), chemical control has had some 

success, and a variety of insecticides have been suggested. Spraying of the chemicals is targeted 

to diapausing adults by trunk application or foliar pesticide application during oviposition 

(EFSA, 2019). 

The Department of Agriculture and Fisheries, Queensland Australia (DAF, 2017), stated that, 

chemical sprays used to control other mango pest can also be used to kill adult mango stone 

weevils using one or two targeted sprays at the start of egg-laying. Reddy et al. (2018), 

suggested, spraying with deltamethrin when fruit are at marble stage as a management measure 

and added that, during the off-season, other pesticides used to control other pests should be 

applied to the trunk to kill adult weevils.  

Balock & Kozuma, (1964), added that, a number of pesticides have been tested for controlling 

adult mango stone weevils, particularly during the mango crop's flowering and fruiting periods. 

These insecticides, which includes Acephate, thiamethoxan, carbaryl, deltamethrin, 

dimethoate, endosulfan, ethofenprox, fenthion, fenvalerate, imidacloprid, monocrotophos and 

prothiofos have been effective in minimizing stone weevil populations and fruit infestations, 

and are all treated at least twice throughout flowering (Verghese et al., 2005b; Akotsen-Mensah 

et al., 2017). 

Ravinshankar and Misra (2010), reported that, spraying of carbaryl (0.2%) or fenthion (0.1%) 

on the stem, branches and fallen leaves kills hibernating adults. They further recommended the 

spraying of fenthion (0.1%) or deltamethrin (0.0025%) at the time of egg laying when fruits 

are of marble size.  Muriuki (2011), in his work on mango production practices and assessment 

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of chemical and physical barriers in the management of MSW, concluded that, trunk painting 

using chlorpyrifos ones per month during the fruiting period is most effective treatment for 

controlling MSW. Aboagye et al. (2014), suggested that insecticides such as alpha 

cypermethrin, acetamiprid and fenithion plus fenvalerate at different doses are effective in 

controlling MSW.    

2.6.4.2 Biological control method 

Peng and Christian (2004), in their research on the integrated control of mango seed weevil 

using weaver ants (Oecophylla smaragdina) as a major component in the Northern Territory 

of Australia reported that, the weaver ant (Oecophylla smaragdina) is an effective biocontrol 

agent of the mango stone weevil adults. In 2007, Peng and Christian again, established that, 

the weaver ants worked as predators and deterrents, reducing mango stone weevil damage. 

Mango stone weevil are often caught by the weaver ants on tree trunks. On the contrary, Louw 

(2008), stated that, the mango stone weevil has no natural enemy.  

Shukla et al. (1984), reported a baculovirus which attacks the larvae of MSW. Verghese et al. 

(2002), in their field survey, discovered a fungus-infected (Beauveria bassiana) dead weevil. 

In South Africa, strains of Beauveria bassiana have been tried on mango seed weevil adults. 

In a laboratory test, two strains caused 30% mortality within 14 days, none of the strains 

however, had an effect on the mango seed weevil in an orchard (Joubert and Labuschagne, 

1995). 

Pena et al, (1998) and Peng and Christian (2007), however, revealed that the mango stone 

weevil's effectiveness as a pest can be linked to the fact that it has no efficient natural enemies 

as they have not been capable of providing sufficient control. 

 

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https://www.cabi.org/isc/datasheet/16434#31992484-7F67-45EC-9078-8D6E080A813E
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2.6.4.3 Cultural control method  

This is a crucial method that involves manipulating the weevil's habitat in order to reduce its 

chances of survival and as a result, enhance the mango plant's healthy growth. Although the 

existing research suggests that farm sanitation as a control measure is ineffectual and labour-

intensive, it is valuable for its contribution to an integrated approach to the sustainable 

management of the mango stone weevil (Pena et al., 1998). 

Monitoring for egg laying markings on young fruits can help detect stone weevil attacks 

(Infornet.biovision, 2019). Good sanitation by collection and destruction of all scattered fallen 

fruits can reduce insect population. Chopping them finely or burying them deeply (50cm deep) 

is advisable. To prevent adult weevils from hiding, orchards should be cleansed of fallen fruits, 

seeds, and plant debris (Peng and Christian, 2004). Stopping the movement of fruits from 

known infested areas to uninfected areas and young orchards free of the seed weevil will greatly 

reduce the chance of infestation.   

Braimah et al., (2009), further stated that, pruning allows adequate light and ventilation into 

the tree canopy, resulting in a less humid microclimate within the canopy, making weevil 

aestivation less suited. Refusing to remove tall weeds decreases air movement and makes a 

plantation's environment damp, favouring the weevil. However, Hansen and Amstrong (1990), 

reported that no significant reduction in weevil populations was recorded in Hawaii in research 

which employed the cultural control method.  

2.6.4.4 Pest resistant varieties 

According to Godse and Bhole (2003), out of ninty two (92) cultivars used in research in India, 

only ten (10) were noted to be free from Sternochetus mangiferae infestation. Grove et al. 

(2007), proposed that, cultivars that produce no seed, form seeds with a hard or insect-toxic 

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shell early, or fruit off season are all potential mechanisms of host plant resistance. Obeng-

Ofori (2007), also added that, mango cultivars that are resistant to the mango stone weevil and 

have favourable features such as seedless, early seed formation and fruiting out of season would 

be valuable.  

Although most cultivars are susceptible to the stone weevil infestation (Hansen et al, 1989; 

Akotsen-Mensah et al., 2017), it is said that larval entry into Itamaraca seed is impossible 

(Balock and Kozuma, 1964; Akotsen-Mensah et al., 2017). In Ghana, the only variety that is 

near seedless, though it does not meet export requirements is Jacqueline. Braimah and Van 

Emden (2010), stated that, there are no cultivars in Ghana that bear fruit on a regular basis 

during the off-season.  

2.6.4.5 Physical and Mechanical control  

These are techniques that physically prevent pests from gaining access to their host. (Mahr, 

2007). Mechanical control has relatively little impact on the beneficial natural enemies of pests 

and other non-target organisms (Mahr, 2007). Elshafie (2019), explained that mechanical and 

physical controls make the environment unsuitable for pests, by restricting them from obtaining 

their resources. Important biological aspects of pests, such as feeding, reproduction, dispersal, 

and survival, are also affected by these approaches.  

Sticky band is an example of the barriers that are used in the control of insect pest. Deep Green 

Permaculture (2019) described the sticky band as an aggressive long-lasting adhesive in the 

form of a waterproof band covered in horticulture glue wrapped around the tree's trunk to 

produce a sticky barrier that keeps climbing insects out of the tree canopy where they can feed, 

mate, and lay eggs. According to Infornet.Biovision (2019), Sticky bands should be put to the 

upper end of the trunk before it branches to prevent weevils from traveling to the branches to 

lay eggs. CCALS (2020), added that, the sticky band act as both a monitoring and a 

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management tool. Even though these weevils are not strong fliers, some reports claim that, they 

can fly, and even with the banding, they might infest the trees (Infornet.Biovision, 2019).  

Research conducted on spotted lanternfly by the CCALS (2020), revealed that, sticky band 

cannot provide a sole source of management because once the sticky band is full, the remaining 

nymph are far less to become stuck. The researchers further stated that, sticky band are also 

less effective on fourth instar nymph and adults which are either strong enough to walk across 

band without getting stuck or avoid them by jumping or flying.  Swackhamer (2018), reported 

that, one disadvantage of utilizing sticky bands is that it can capturing other creatures of which 

some could be beneficial.  

Brigham and Smishek (1991) suggested that a substitute for the adhesive band (tangle trap) 

may be the automotive lubricating grease. The grease has a low cost, good water resistance, 

and excellent long-term adhesive capabilities. Horticultural glues should never be applied 

directly to a tree's bark, as trees with thin bark, particularly young trees, can be sensitive to 

such application. The tree will be ring-barked and die if the bark is injured all the way around 

its circumference (Deep Green Permaculture, 2019).  

2.6.4.6 Quarantine and phytosanitary measures 

Phytosanitary measures are quarantine and biosecurity measures which are used to safeguard 

the lives of humans, animals, and plants life from risk arising from the introduction, 

establishment and spread of pest and diseases arising resulting from food and feed additives, 

poisons and pollutants (Agriculture.gov 2020). According to FAO (2003), a quarantine pest is 

a pest that has the potential to be economically important to the area threatened by it but is not 

yet present or is present but not widely disseminated and is under official control. 

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Braimah and Van Emden (2010), stated that, phytosanitary measures aim at eliminating, 

regulating pests in exported fruits by sterilizing or killing them to prevent their introduction 

and establishment in new locations. The mango stone weevil is a major pest with a 1:40 

rejection rate in international quarantine (Braimah et al, 2009).  

CABI and EPPO (2015), reported that, fruits, mango seeds and plants provide a phytosanitary 

threat and as such mango-growing countries may exclude materials from countries where the 

pest is present. Fruits imported from countries where Sternochetus mangiferae is found may 

be quarantined.  

Mango stone weevils are thought to spread into clean areas by the transit of contaminated fruit 

for propagation and consumption, according to available evidence. Even in seed weevil-

infested locations, young orchards planted from weevil-free nursery stock have been 

demonstrated to be seed weevil-free for several years after planting. (DAF, 2017). 

2.7 Detection of mango stone weevil within the fruit  

The mango stone weevil spends a significant period of its life cycle in the mango fruit and has 

been described by several researchers as an insect pest that solely depends on mangoes for 

survival. Its attribute of growing mainly inside the fruit usually in the seed, makes it difficult 

to determine whether a fruit is free from the weevil or not. Farmers in Ghana most often than 

not turn to cut open sampled fruits to determine whether they are infested or not. According to 

Sambrani et al., (2015), mango varieties that have seed weevil or stone weevil infestation, are 

not visible externally in Indian mangoes.  

Infornet.Biovision (2019), stated that, Fruit infestation at a later stage is difficult to identify 

because there is no visible evidence of infestation other than an inconspicuous egg laying scar, 

and subsequent feeding activity in the seed stays unnoticed. It is impossible to tell the difference 

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between infected and uninfected seeds unless they are cut open. A seed splitting equipment is 

essential for detection because contaminated fruit is normally not visibly harmed (Woodruff 

and Fasulo, 2006). Thomas et al. (1995), also said that mango fruits infected with seed weevil 

have no evident outward signs of infestation but generate significant concerns. 

In research to determine the presence of mango stone weevil in Thailand, Unahawutti et al. 

(2005), resorted to cutting sampled fruits longitudinally open to inspect seeds for presence of 

the mango weevils. Follet (2002), reported that, as the fruit and seed mature, the weevils' 

tunnels and stationary spots are completely healed. This makes distinguishing between infested 

and non-infested fruits impossible unless the fruits are disserted to expose the state of the 

internal structures. (Follet, 2002).     

Peng and Christian, (2007), on the contrary, stated that, the hardened, amber-coloured 

secretion, which is sometimes sculptured with two angled tails at one end and remains attached 

to the site of oviposition, distinguishes afflicted fruits from uninfected ones. Maheswari and 

Purushottham (1999), stated that, the presence of reddish-brown patches and water-soaked 

areas in the pulp of immature mango fruits is a quick way to diagnose the presence of MSW in 

fruits. 

Sambrani et al. (2015), reported that, an effective and accurate solution that can detect spongy 

tissue and seed weevil infested mangoes was by instrumental means and grading good quality 

mangoes for consumption and export. Sambrani et al. (2015), therefore proposed the use of a 

totally non-destructive indigenous technology which employs Digital X-ray imaging. The 

researchers added that, mangoes that have been scanned with a digital X-ray are safe to eat and 

pose no health risks.  

According to Thomas et al, (1995), because of feeding by developing larvae, an X-ray 

radiograph of infested mangoes shows dark regions in the seed corresponding to distinct kernel 

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tissues. Non infested mangoes on the other hand, display a light-grey region that represents a 

wholesome kernel. A high degree of agreement was detected between X-ray images of fruits 

exhibiting weevil infestation and physical examination of cut fruits, suggesting the technique's 

trustworthiness. As a quality control method, X-ray imaging has a lot of potential in the 

processing sector and the export trade (Thomas et al, 1995).   

   

 

 

 

 

 

 

 

 

 

 

 

 

 

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CHAPTER THREE 

3.0 MATERIALS AND METHODS 

3.1. Study Areas 

The study was conducted in the eastern mango enclave of Ghana where mango is cultivated on 

a large scale for commercial purpose. The study was mainly concentrated in the Yilo Krobo 

Municipality in the South-Eastern part of Ghana. The municipality lies between latitude 60o 

00’ south and 00o 30’ North and between longitude 00o 30’ east and 10o 00’ west. It covers an 

area of about 805km2 which forms about 4.2% of the total land area of the Eastern region 

(ERCC, 2016). 

The Municipality shares border with Upper Manya Krobo on the north, Lower Manya Krobo 

to the east, Akwapim North Municipality and Shai-Osudoku District on the south, New 

Juabeng Municipal and East Akim Municipal on the west and Fanteakwa District on the north-

west.  

The rainfall pattern of the Municipality is bi-modal and reaches its maximum during the two 

peak periods of May – June and September – October. The annual rainfall ranges from 750 to 

1600mm. Temperature ranges between 24.9oC and 29.9oC (ERCC, 2016). 

The Yilo Krobo Municipal District lies within the semi-deciduous rain forest and the coastal 

savannah zone. Most common trees found in the municipality include oil palm, mango, nim, 

ceiba and acacia. And these factors underline the selection of the Yilo Krobo Municipal District 

as suitable place for carrying out this experiment. These attributes according to Aboagye 

(2009), makes the study area one of the few mango-growing areas assured of double harvest 

annually, with the major season falling between May-July and the minor harvest between 

October – November. Although the research was mainly conducted in the Yilo Krobo 

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Municipal District, the survey to investigate mango stone weevils took the researcher as far as 

Todekofe (Pricon Farms, N6o12’44.3484” E0o6’42.318”) in the Asuogyaman District. 

 

Figure 3.1: Map of the study area. 

 

The research work had four components (i.e., administration of questionnaire to evaluate the 

knowledge, attitude and practice of farmers in the management of mango stone weevil, a field 

survey to investigate the level of mango stone weevil infestation, application of different 

treatments to control the mango stone weevil and a non-destructive detection of mango stone 

weevils in fruits). 

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3.2 Knowledge, attitude and practices of mango farmers towards mango stone weevil 

and its management.   

Farmers from the Yilo Krobo Mango Farmers Association (YKMFA) were randomly selected 

for the study to answer questionnaires with the objective of investigating farmers’ knowledge, 

attitude and practice on the mango stone weevil (MSW) and its level of infestation on the field. 

The questionnaire was made up of twenty-three (23) questions which boarded on the biodata 

of respondents, knowledge on MSW and their management, farmer’s attitude towards MSW 

and their management and MSW management practices. The questions were made up of 

twenty-one (21) select type objectives of which respondents had alternative answers to choose 

from. Farmers offered their own replies to the remaining questions, which were of the supply 

type. The questionnaires were translated into Akan (Twi) and Dangme for farmers who were 

unable to read and write in English. 

3.3 Survey of mango stone weevil infestation 

To determine the extent of the mango stone weevil infestation, a survey was conducted within 

the Eastern Mango enclave of Ghana, thirty (30) mango orchards were visited during the minor 

and major season after interacting with farmers through questionnaire administration. 

Farms visited were located at villages near Somanya such as Akode, Alorley, Akuse road, New 

Somanya, Akode, Agomada, Asesease and Todekofe near Juapong. A greater percentage of 

the farms were however, located in the Yilo Krobo municipality. Thirty (30) farmers were 

visited on their farms during the minor season between November, 2019 and January, 2020 

when greater percentage of fruits were fully matured. On each selected farm, fifty (50) matured 

fruits that have dropped were picked at random and disserted using a cutlass to check mango 

MSW infestation. In instances where the mango stone weevil was present, record was taken on 

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the developmental stage of the insect. Where fruits had exit holes but no insect present, they 

were considered as infested, and the stage of development recorded as adult.   

The visits were repeated during the major season between May – July, 2020. These farmers 

were selected based on accessibility to their farms. Below is a table of farm sampled for the 

survey. 

Table 3.1: List of communities captured during the survey    

Town (community) Number of farmers 

Akorley  6 

New Somonya 7 

Akuse Road 8 

Akode  6 

Agomada 1 

Asesease  1 

Todekofe  1 

Total 30 

 

3.4 Evaluation of different management methods against the mango stone weevils  

Treatments applied to manage (trap or kill) mango stone weevil included Sticky band, Grease, 

Chlorpyrifos (Dursban 4EC) and a control. The sticky band and chlorpyrifos were purchased 

from Agrimat at Firestone near Madina - Accra whiles the grease was obtained from Goil filling 

station, Aburi. The Modest Step Farm (N6o2’19.644” W0o0’9.67788”) at Akorley was selected 

for the evaluation of the different management methods due to the presence of the weevils on 

this farm and its accessibility. These treatments were applied on fifteen (15) trees in total (i.e., 

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each treatment had five replications). Trees that received the treatments were sampled in a ‘W’ 

patterned transect.  

After the application of treatments, ribbons were used to identify the mango trees on which 

treatments were applied and labelled. The orchard was visited every week until maturity and 

ten (10) dropped fruits from each selected tree were cut into two halves in a longitudinal cross-

section. Any larvae, pupae or adult present were collected and preserved in a micro centrifuge 

tube containing 70% alcohol.  

Data collection lasted eight (8) weeks from 30th November, 2019 to 18th January, 2020 and 

repeated on 6th May to 24th June, 2020 for the major season. The treatments were reapplied on 

different trees on the same farm during the major season between May – July 2020.  

3.4.1 Sticky Band 

The sticky band is made up of a PVC sheet of dimension of 26cm×40cm (0.104m2) with 

tanglefoot (a sticky material) applied to both sides. It is sticky on both sides making it very 

efficient in trapping insect pest that land or crawl on the surface. A pair of scissors was used to 

cut the sticky band longitudinally to a dimension of 13cm×40cm (0.52m2). The sticky band 

was cut to make it sizeable and to reduce wastage since the target insect (i.e., the adult mango 

stone weevil) is about 8mm long (Infornet.Biovision.com). It was then fastened around the 

trunks of selected mango trees about 1m above the ground using 1inch long nails and a hammer 

to cover the entire circumference of the trunk. Five trees received the treatment, and each tree 

represented a replicate. Monitoring was done for eight weeks and observations such as trapped 

insects and their status (i.e., harmful or beneficial were recorded). 

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Figure 3.2: A mango tree with sticky band 

 

3.4.2 Chlorpyrifos (Dursban 4EC) 

Dursban 4EC (chlorpyrifos), a broad spectrum organophophate insecticide was diluted with 

water at a concentration of 1.25ml/l and applied on the trunks of selected trees to form a 10cm 

band about 1m above the ground. Great caution was taken to cover the entire circumference of 

the trunk and for the insecticide to enter all cracks and crevices on the trunk.     

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Figure 3.3: The trunk of a mango tree treated with chlorpyrifos  

 

3.4.3 Grease banding 

An automobile lubricating grease which is usually used by mechanics in lubricating machines 

was used as the third treatment in this research. The grease was applied to the trunks of five (5) 

selected mango trees around the circumference using a home-made scraper. The treatment was 

applied such that it was about 0.5mm thick and 5cm wide. Five (5) other mango trees were 

selected as control plants on which no treatment was applied.   

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Figure 3.4: The trunk of a mango tree treated with grease 

 

3.5 Non-Destructive Detection of Internal infestation of Mango Stone Weevil  

The mango stone weevil spends greater part of its life cycle within the mango fruit, accounting 

for the difficulty in controlling it. Since it lives within the fruits, local farmers find it difficult 

to detect it unless they dissect sampled fruits. This further increases the post-harvest losses 

during the supply chain. As a result, a scanner using a soft X-ray was used to pick images of 

fruits that were harvested from mango trees.  

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Ten (10) fruits randomly picked from an infested farm and sent to the laboratory (in brown 

envelops). At the laboratory, the fruits were washed in salt solution (at a concentration of 

500g/l), cleaned and place in new envelops and labelled. The fruits were then sent to the 

medical laboratory where X-ray images of the fruits were taken. The specification of the X-ray 

image was voltage = 50kv, current = 10mAs and exposure time = 4s. Just after the X-rays were 

taken the fruits were immediately dissected to enhance easy comparison of fruits (i.e., whether 

infested or uninfected) and the content thereof with the image captured.  

3.6 Data Analysis 

Qualitative and quantitative data collected through questionnaire administration and data 

collected during survey was analysed with descriptive statistics in frequencies and percentages 

using the statistical package for social science students (SPSS) statistics for window, version 

25.0. Chi-square was used to determine the association between demographics of respondents 

and farm management practices.  

Data collected in evaluating different management methods against the mango stone weevil 

was subjected to analysis of variance (ANOVA) test and treatment means were separated using 

LSD at 0.05%. Normality and Homogeneity of data was done using Shapiro-Wilk test for 

Normality and Bartlett's test for homogeneity of variances respectively, using GenStart 

software 12th edition. Microsoft excel spreadsheet was used in preparing the bar graphs and pie 

charts.         

 

 

 

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CHAPTER FOUR 

RESULTS 

4.1 Knowledge, attitude and practices of mango farmers towards mango stone weevils. 

4.1.1 Demographic characteristics of mango farmers.  

Respondents’ demographic characteristics were very essential to the research because it could 

influence how respondent’s mange the mango stone weevil, control other insect pest and the 

acreage they cultivate. 

The result of socio-demographic characteristics of mango farmers interviewed on the field 

showed that, 90% of the respondents were male while the remaining 10% were females.  

A greater number of respondents fell outside the youth bracket. Sixty percent of respondents 

were aged, 36.7% were adults and 3.3% of the respondents were youth.  

 

Figure 4.1. Age of respondents 

 

Data obtained from the questionnaire showed that 30% of mango farmers had Basic Education. 

40% have experienced secondary education (i.e., vocational school, technical school and 

3.3%

36.7%

60%

Youth (Less than 25yrs) Adult (25-50yrs) Aged (Over 50yrs)

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secondary school), while the remaining 30% are products of tertiary institutions (i.e. College 

of Education, Nursing Training, Agricultural Colleges, Poly-techniques and Universities).  

The finding from the Chi-Square analysis showed that, the educational background of the 

respondent is independent of the annual income from fruit sales. Meaning that farmer’s level 

of education had no bearing with annual income from sales as a farmer. 

A mean of 2.97 was recorded as the number of years a farmer has been involved in mango 

farming. Seventy percent of farmers had cultivated mangoes for 11-20years. Thirteen percent 

of respondents said they have 5-10years experience in mango farming. Ten percent of the 

farmers interviewed also said they have farmed mango for 21-30years. Three-point three 

percent of the respondents said they have cultivated mangoes for less than 5years and over 

30years in each case. 

The evidence obtained suggests that the respondent's farm size has nothing to do with the 

number of years he or she has been farming. It implied that, the number of years of farming 

has correlation with farm size.  

Table 4.1. Number of years in mango farming  

           Years           Frequency  Percent  

 Less than 5yrs             1  3.3  

5-10yrs             4  13.3  

11-20yrs           21  70.0  

21-30yrs             3  10.0  

Over 30yrs             1  3.3  

Total           30  100.0  

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4.1.2 Farm size and mango varieties on the farms captured in the survey 

At the end of the survey, it was revealed that, 53.3% of the respondents were medium scale 

farmers, 33.3% were large scale farmers whiles the remaining 13.3% were small scale farmers. 

 

Figure 4.2: Farm size of respondents 

  

The research brought to light that, 36.7% of the farmers interviewed, were in the cultivation of 

the Keitt variety. Thirty-three-point three percent were growing Keitt and Kent on their farms. 

Ten percent cultivated Keitt, Kent and Palmer. Six-point seven percent had Keitt, Kent, Haden, 

and Palmer. Three-point three percent of the farmers were found to be involved in the 

cultivation of Kent only, Keitt and Haden, Keitt, Kent, Haden and Springfels, and Keitt, Kent, 

Haden, Sunset, Palmer, Springfels and Amilie in each case. 

13.3%

53.3%

33.3% Less than 5acres

5 - 20 acres

Greater than 20 acres

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52 
 

 

Figure 4.3: Mango varieties cultivated by farmer  

Response from farmers showed that, 40% of farmers cultivated two varieties on their farm. 

Thirty-six-point seven percent of respondents planted only one variety. Thirteen-point three 

percent were manging more than three mango varieties. The remaining 10% of the respondents 

were growing three varieties of mango on the same farm. 

3.3

6.7

3.3

10

3.3

33.3

3.3

36.7

0

10

20

30

40

50

60

70

80

90

100

Keitt,

Kent,

Haden and

Springfels

Keitt,

Kent,

Haden,

Palmer,

Sprinfels

and Amilie

Keitt,

Kent,

Haden and

Sunset

Keitt,

Kent, and

Palmer

Keitt and

Haden

Keitt and

Kent

Kent Keitt

F
ar

m
er

s

Varieties of mango in cultivation

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53 
 

 

 

4.1.3. Farmers’ knowledge on pest and pest control. 

All the respondents (100%) interviewed in the research, stated that, they encounter pest on their 

respective farms. 

Fruit flies and mango stone weevils were identified by 36.7% of the respondents as the 

main types of pests often encountered on mango farms. Sixteen-point seven percent of the 

farmers pointed fruit flies, mealy bug and mango stone weevil, and fruit flies and mealy bugs 

as the pest they often come across in each case. Six-point seven percent of the farmers said 

fruit flies only and mango stone weevil only in each case are the pest frequently encountered.  

 

40
36.7

10
13.3

0

10

20

30

40

50

60

70

80

90

100

One variety Two varieties Three varieties More than three

varieties

F
ar

m
er

s

Number of varieties

Figure 4.4: Number of mango varieties cultivated by farmers. 

 

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Table 4.2: Pests encountered by farmers 

             Pest         Frequency                Percent 

 Fruit flies          2          6.7 

Fruit flies, MSW and Aphids          1          3.3 

Fruit flies and Mealy bug          5        16.7 

Mealy bug and Aphids                                    1          3.3 

Fruit flies, Mealy bug and Aphids          1          3.3 

MSW          2          6.7 

Mealy bug          1          3.3 

Fruit flies and MSW        11        36.7 

Fruit flies, MSW and Mealy bug          5        16.7 

Fruit flies, MSW, Mealy bug, 

Aphids and Coconut bug 

         1         3.3 

Total        30           100.0 

All the thirty farmers (100%) used in the survey, knew about the nuisance posed mango stone 

weevil as a pest of mango. Almost eighty-seven percent of the farmers stated that, the mango 

stone weevils were present on their respective mango farms. Thirteen-point three percent of 

the respondents however, stated the contrary. 

Twenty farmers, representing 66.7% of the respondents said the mango stone weevil are still 

present on their individual farms. Twenty percent of respondents said, the mango stone weevils 

do not persist on their farms anymore. 

In the control of the mango stone weevil, 50% of the respondents on whose farms the mango 

stone weevils were not persisting stated that, they used chemical method in controlling the 

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mango stone weevil. Forty percent of respondents also said they used both chemical and 

cultural method. Ten percent on the other hand said, they used the integrated pest management 

method. 

There is no significant association between how farmers control MSW and Annual expenditure 

on MSW control. Here, it can then be concluded that controlling MSW is not likely linked with 

annual expenditure on MSW control. 

Table 4.3: Control measures employed by farmers in controlling MSW 

Control measures Frequency Percent 

Chemical Control 5 16.7 

Integrated Pest Control Method 1 3.3 

Chemical and Cultural Method 4 13.3 

Total 20 33.3 

Missing System 10 66.7 

Total 30 100 

 

4.1.4. Pest and pest management on mango farms in the study area. 

Thirty-seven percent of the farmers stated, they apply control measures at the flowering stage 

and after harvesting of fruits. Sixteen-point seven percent of the respondents said they control 

the mango stone weevil at the flowering stage. Respondents that applied control measures after 

harvesting were also sixteen-point seven percent. Farmer that applied the control measure at 

the golf ball size stage were 10%. About seven percent of respondents applied control measure 

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at flowering stage and golf ball size stage, and full maturity stage in each case. Three-point 

three percent of the farmers disclosed they controlled the pest at the tennis ball size stage, and 

the flowering stage, tennis ball size stage and the full maturity stage in each case.    

 

About fifty-three percent of the respondents had view that, the mango stone weevil attacks at 

the golf ball size stage. Thirteen-point three percent of the farmers also said the pest attacks at 

the flowering stage, and the flowering and golf ball size stages in each case. Ten percent of 

respondents indicated that, the mango stone weevil often attacks at the tennis ball size stage. 

Three-point three percent were of the view that, the pest in discussion attacks at full maturity, 

flowering stage and tennis ball size stage, and flowering stage, tennis ball size stage and full 

maturity in each case. 

16.7

10

3.3

16.7

6.7 6.7

36.7

3.3

0

10

20

30

40

50

60

70

80

90

100

Flowering Golf ball Tennis ball After

flowering

Flowering

and Golf

ball

Flowering

and Full

maturity

Flowering

and After

harvesting

Flowering,

Tennis ball

and Full

maturity

F
ar

m
er

s

Developmental stage of mango fruits

Figure: 4.5. Time farmers usually control MSW.

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Figure 4.6: Developmental stage of mango fruit at which MSW usually attacks. 

One hundred percent of the farmers interviewed said they sample some fruits from their farms 

and dissect to determine whether it is infested or not. The seeds of the dissected fruits were 

then inspected to see the presence of the weevil or otherwise.  

In responds to the question as to whether the mango stone weevil is a major insect or not, 76.7% 

of the farmers described the mango stone weevil is a major pest. The remaining 23.3% said the 

mango stone weevil is not a major pest. 

Thirty-seven percent of respondents said they see mango stone weevil as major pest because 

it’s a quarantine pest. Thirteen-point three percent of the respondents said, the pest is a major 

pest in mango production because, it’s difficult to detect, and difficult to control in each case. 

13.3

53.3

10

3.3