University of Ghana http://ugspace.ug.edu.gh RELATIVE ABUNDANCE OF MIRIDS OF COCOA IN DIFFERENTLY MANAGED SYSTEMS IN THE EASTERN REGION OF GHANA BY DARKO OKYERE JAMES 10395317 THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF MPHIL ENTOMOLOGY DEGREE INSECT SCIENCE PROGRAMME UNIVERSITY OF GHANA Joint Interfaculty International Programme for the Training of Entomologists in West Africa. Collaborating Departments: Animal Biology and Conservation Science (faculty of science) and Crop Science (School of Agriculture, College of Agriculture and Consumer Sciences) University of Ghana, Legon JULY, 2014 University of Ghana http://ugspace.ug.edu.gh DECLARATION This is to certify that this thesis is the result of research undertaken by me, Darko Okyere James towards the award of Master of Philosophy in Entomology in African Regional Postgraduate Programme in Insect Science (ARPPIS), University of Ghana, Legon. This thesis has not been submitted either in part or in full for any other degree and all references to other peoples work have been duly acknowledged. …………………………………………………………… DARKO OKYERE JAMES (STUDENT) …………………………………………………………....... PROFESSOR KWAME AFREH - NUAMAH (SUPERVISOR) ………………………………………………………………. DR. RICHARD ADU - ACHEAMPONG (CO-SUPERVISOR) ………………………………………………………………... DR. ROSINA KYEREMATEN (ARPPIS CO-ORDINATOR) i University of Ghana http://ugspace.ug.edu.gh ABSTRACT The temporal distribution of four important cocoa mirid species (Distantiella theobroma Dist, Sahlbergella singularis Hagl, Helopeltis bergothii and Bryocoropsis laticollis) was studied in three differently managed cocoa farming systems from May 2013 to April 2014. In addition, the incidence of Bathycoelia thalassina, Characoma stictigrapta, Anomis leona, Earias biplaga, Eulophonotus myrmeleon, Oecophylla longinoda and Crematogaster africana, were recorded. The three systems were: Organically managed cocoa farms located at Akwadum, Experimental farms at CRIG, Tafo and Farmer‟s farms also at Tafo. Each system was replicated three times each of size one acre with an average of five hundred (500) cocoa trees. Sampling was done monthly on one hundred (100) randomly selected tagged cocoa trees per farm. Parameters which were assessed over the period included: population counts of mirids, incidence of other insect pests and natural enemies as well as climatic data on Rainfall, Temperature and Relative humidity. Records of insects were made from visual counting from the base of the cocoa tree to hand height (2 m) of each of the tagged trees. The owners of the farms were also interviewed on the type of farming systems they operate, knowledge on good agricultural practices and pesticides use pattern. The Organic and the Farmer‟s farms recorded the highest mirid numbers in September with peak populations of ninety nine (99) and fifty eight (58) respectively per three hundred (300) cocoa trees. The Experimental farms recorded the lowest mirid population of fifty (50) per three hundred (300) cocoa trees with the peak population occurring in March. Both the organic and Farmer‟s farms showed a similar trend in the distribution of mirids with the highest peak occurring in September. In addition the incidence of Bathycoelia populations found in the Farmer‟s ii University of Ghana http://ugspace.ug.edu.gh farms, Experimental farms and the Organic farms were twenty eight (28), seventeen (17) and six (6) respectively per three hundred (300) cocoa trees. Two seasonal peaks of Bathycoelia were observed in all the three farming systems with the highest peak occurring between May and August and the second between January and April. The number of pods damaged by Bathycoelia was high even at low pest densities. The organic and the Farmer‟s farms recorded the highest of 50 and 45 pod damage per 300 cocoa trees in September with the Experimental farms recording 11 in October which was the highest over the period. There were 57, 55 and 29 individuals of Characoma per 300 cocoa trees in the Organic, Farmer‟s and Experimental farms respectively. The number of Cocoa trees with mealybugs out of 300 trees per plot were 123, 94 and 29 for Organic, Farmer‟s and Experimental farms, respectively. There was a negative correlation between natural enemy population and pest incidence. Peak relative humidity data of 86.7% and 83.8% were recorded in July and August and the lowest temperature of 28.5C was also recorded in the same months favouring the multiplication of mirid numbers. iii University of Ghana http://ugspace.ug.edu.gh ACKNOWLEDGEMENTS I am extremely grateful to my supervisors Prof. Kwame Afreh-Nuamah and Dr. Richard Adu Acheampong for their guidance and useful suggestions. My sincere thanks also goes to the Executive Director of Cocoa Research Institute of Ghana for permitting me to carry out this research work in their premises and also providing me with labour and transport every month to the various farms. I am also grateful to Dr. Emmanuel Agyemang Dwomoh, Dr. Ernest Felix Appiah and Mr. Godfred Awudzi for their interest in the study and for their valuable suggestions. My appreciation also goes to Messrs. Ebenezer Kwapong, and Emmanuel Owusu of the Entomology division at CRIG for assisting me in the assessment of mirid populations, as well as in the area of insect identification. My appreciation also goes to the cocoa farmers whose cocoa farms were used for the survey especially the chairman of the cocoa organic farmers association (COFA) Mr. Francis Otu Acquah for his assistance in selecting the farms. My special commendation also goes to my mother Mrs Victoria Darko, father Mr E. O. Darko and siblings for their generous support and prayers during my writing up period. I am also grateful to my wife Abigail Okyere Darko and two children Kwabena Ampem Darko Okyere, Kofi Amakye Okyere Darko and Naana Asah Okyere Darko for their encouragement and spiritual support. iv University of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENTS Content Page Declaration ........................................................................................................................... i Abstract ............................................................................................................................... ii Acknowledgements ............................................................................................................. v DEDICATION…………………………………………………………………………………………………………………………………. Table Of Contents ............................................................................................................... v List Of Tables .................................................................................................................. viii List Of Plates....................................................................................................................... x CHAPTER ONE ................................................................................................................. 1 1.0 Introduction ................................................................................................................... 1 1.1 Justification ................................................................................................................... 3 1.2 Objectives .................................................................................................................... 4 1.2.1 Main Objective ....................................................................................................... 4 1.2.2 Specific Objectives ................................................................................................. 4 v University of Ghana http://ugspace.ug.edu.gh CHAPTER TWO ................................................................................................................ 6 2.0 Literature Review.......................................................................................................... 6 2.1 Dynamism in insect pests control ................................................................................. 6 2.2 Theobroma Cacao: Origin And Description ................................................................. 9 2.2.1Classification Of Cocoa ........................................................................................ 11 2.2.2 Cultivation Of Cocoa ........................................................................................... 12 2.2.3 Cocoa Production In Ghana ................................................................................. 13 2.2.4 Economic Importance Of Cocoa .............................................................................. 14 2.3 Cocoa Insect Pests....................................................................................................... 15 2.3.1 Cocoa Mirids ....................................................................................................... 16 2.3.2 Mirid Damage ...................................................................................................... 17 2.3.3 Ecology Of Cocoa Mirids .................................................................................... 18 2.4 Shield/Stink Bug, Bathycoelia Thalassina(Hs.) (Hemiptera:Pentatomidae) .............. 19 2.5 Podborer, Characoma Stictigrapta Hmps (Lepidoptera: ............................................ 20 Noctuidae) ......................................................................................................................... 20 2.6 The Cocoa Stem Borer, Eulophonotus Myrmeleon .................................................... 21 2.7 Termites Macrotermes Spp( Isoptera: Termitidae) ..................................................... 22 2.8 Anomis Leona Schauss And Earias Biplaga Wlk ...................................................... 23 2.9 Aphids (Toxoptera Aurantii) And Psyllids ................................................................. 25 2.10 Mealybug Vector For CSSV ................................................................................... 25 2.11 Beneficial Fauna In Cocoa Ecosystem (Ants Mosaic) ............................................. 28 2.12 Recommended Management Practices In Cocoa Farms ........................................... 31 2.12.1 Weed Control ..................................................................................................... 31 2.12.2 Pruning ............................................................................................................... 32 vi University of Ghana http://ugspace.ug.edu.gh 2.12.3 Shade Management ............................................................................................ 32 2.12.4 Insect Pests Control ............................................................................................ 33 CHAPTER THREE .......................................................................................................... 34 3.0 METHODOLOGY .................................................................................................... 34 3.1 Experimental Period.................................................................................................... 34 3.2 Study Site .................................................................................................................... 34 3.3 Sampling of Mirids and other insects of cocoa ........................................................... 37 3.4 Statistical Analysis ...................................................................................................... 37 CHAPTER FOUR ............................................................................................................. 38 4.0 RESULTS ................................................................................................................... 38 4.1 Management practices in Organic, CRIG And the Farmer‟s Farms . Error! Bookmark not defined. 4.1.1 Organic farms ........................................................ Error! Bookmark not defined. 4.1.2 Farmer‟s farmers ................................................... Error! Bookmark not defined. 4.1.3 Experimental farms .............................................. Error! Bookmark not defined. 4.2 Mirids Population........................................................................................................ 38 4.2.1 Trend of S. Singularis populations in the three sytems compared. ...................... 39 4.3 Other insect pests of cocoa population studies ........................................................... 41 4.4 Natural enemies temporal distribution ........................................................................ 54 4.5 Mirids population compared to the climatic factors ................................................... 56 4.6 Comparison of Mean S. Singularis population in the three systems .......................... 61 CHAPTER FIVE .............................................................................................................. 61 5.0 DISCUSSION ............................................................................................................. 62 5.1 Management practices in the three systems ................................................................ 62 vii University of Ghana http://ugspace.ug.edu.gh 5.2 Mirids population and trend in the three systems ....................................................... 64 5.3 Other insect pests on cocoa sampled .......................................................................... 67 5.4 Natural enemies populations ....................................................................................... 70 5.5 Influence of climatic factors (Rainfall, Temperature And Relative Humidity) on the population of S. Singularis ................................................................................................ 71 CHAPTER SIX ................................................................................................................. 73 6.0 CONCLUSION AND RECOMMENDATIONS ....................................................... 73 6.1 Conclusion ................................................................................................................... 83 6.2 Recommendations ........................................................................................................ 84 REFERENCES …………………………………………………………………………………………………………………………….86 LIST OF FIGURES Fig. 3. 1 Map of Eastern Region showing Districts surveyed with dots………… 43 Fig. 4.1 Total population of the four species of mirids in the three systems…. 49 Fig. 4.2 Trend of S. singularis populations in the three systems……………….. 51 Fig.4.3: Population of Bathycoelia thalasina in the three systems………….. 52 Fig. 4.4: Trend of Bathycoelia population in the three systems…………….. 53 Fig. 4.5: Trend of Bathycoelia damage pods in the three systems…………….. 54 Fig.4.6: Population of Characoma in the three systems ……………………….55 Fig. 4.7: Trend of Characoma incidence in the three systems…………………. 56 Fig. 4.8: Population of Eulophonotus in the three systems……………………. 57 viii University of Ghana http://ugspace.ug.edu.gh Fig.4.9 Population of Anomis leona in the three systems…………………… 58 Fig.4.10: Population of Earias biplaga in the three systems………………….. 59 Fig.4.11: Population of Termites in the three systems………………………….. 60 Fig.4.12: Number of cocoa trees with Mealybugs in the three systems…………. 61 Fig. 4.13: Trend of mealybugs incidence in the three systems………………….. 62 Fig. 4.14: Number of cocoa trees with Aphids in the three systems……………. 63 Fig.4.15: Number of cocoa trees with Psyllids in the three systems………….. 63 Fig.4.18 Mean monthly climatic conditions during the study period. (Source: CRIG Meteorological Department)…………………………..……. 66 Fig.4.17: Influence of Rainfall on Sahlbergella population in the organic farms... 67 Fig.4.18: Influence of Rainfall on Sahlbergella population in the Experimental farms…... 67 Fig.4.19 Influence of Rainfall on Sahlbergella population in the Farmer‟s farms………………………………………………………………… 68 Fig.4.20: Influence of Temperature on Sahlbergella population in the organic farms………………………………………………………………… 68 Fig.4.21: Influence of Temperature on Sahlbergella population in the Experimental farms……………………………………………………………… 69 Fig.4.22: Influence of Temperature on Sahlbergela in the Farmer‟s farms.. 69 ix University of Ghana http://ugspace.ug.edu.gh Fig.4.22: Influence of Relative Humidity on Sahlbergella in the organic farms. … 70 Fig. 4.24: Influence of Relative Humidity on Sahlbergella in the Experimental farms…… 70 Fig.4.25: Influence of Relative Humidity on Sahlbergella population in the Farmer‟s farm………………………………………………… 71 LIST OF PALTES Plate 1 : S. singularis feeding on cocoa pod……………………………….. ……….18 Plate 2 : B. thalassina on cocoa pod premature ripening of cocoa pod……………..20 Plate 3 : C. stictigrapta larva and damage to cocoa pod…………… ………………..22 Plate 4: Anomis leona on cocoa leaves……………………………………………….24 Plate 5: E. biplaga on cocoa leaves…………………………………………………..25 Plate 5: Planococcoides njalensis on cocoa pod……………………………………28 x University of Ghana http://ugspace.ug.edu.gh CHAPTER ONE 1.0 INTRODUCTION The cocoa plant, Theobroma cacao L. is reported to have been introduced into Ghana in 1879 (Manu and Tetteh, 1987). It is a major cash crop cultivated in the tropical regions of West Africa, the Caribbean, South America and Asia. In West Africa, where over 70% of the world‟s cocoa is produced, it is a significant component of the rural economy, as the industry is dominated by large numbers of smallholder peasant farmers who depend on the crop for their livelihood (Acquaah, 1999; Appiah, 2004). This lower storey rainforest tree is grown in six regions of Ghana namely Eastern, Ashanti, Central, Volta, Brong – Ahafo and Western regions. Ghana is the second largest producer of cocoa beans in the world with a mean annual production of 879,347,90 metric tonnes after Ivory Coast (Cocobod, 2012). Two varieties of cocoa are cultivated in Ghana; Amelonado and Amazon. The amelonado variety is fast being replaced with the amazon hybrids because of superior growth vigour, high bean yield and tolerance to pest and disease (Opeke, 1992 ) Cocoa has been the bedrock of the Ghanaian economy over the last century. It continues to play major roles such as employment creation and earn the nation valuable foreign exchange, thereby providing a significant chunk of government revenue. Research findings indicate that some components in cocoa help to prevent cardiovascular disease. Cocoa beans contain a large number of phytochemicals which are physiologically active compounds found in plants, for example grapes, apple, tea, fruits, vegetables, etc. One group of these compounds is called flavonoids which are powerful anti-oxidants. Studies 1 University of Ghana http://ugspace.ug.edu.gh have indicated that cocoa flavonoids can inhibit the oxidation of the low-density lipoprotein (LDL-cholesterol) associated with heart disease. There is also emerging evidence which suggests that cocoa and chocolate may be able to contribute to reducing the risk of certain types of cancer (ICCO, 2004 ; 2005). The incidence of pests and diseases, low market prices, unavailability of production inputs such as insecticides, fertilizer etc. are among a number of factors negatively affecting cocoa production in Ghana (Anon, 1995). The insect pest complex that causes economic damage to cocoa in Ghana are the mirids or capsids, the mealybugs, Bathycoelia, Characoma, termites and the stem borers (Hill, 1993). In Ghana the brown cocoa mirid, Sahlbergella singularis (hemiptera; miridae) has been reported as the major economic insect of cocoa, capable of reducing yield by up to 30% (Owusu- manu, 2002). Padi (1997) reported a yield loss of 75% in cocoa farms due to attack by mirids in a period of 3 years if left unattended. Chemical control of cocoa mirids, Distantiella theobroma (Dist) and Salhbergella singularis Hagl was initiated when the insects were first recognised as serious pests of cocoa in Ghana (Dudgeon, 1910). The universal indiscriminate use of insecticides and the complications which have followed have directed attention in the last few years, to the need of radical change towards ecology in tackling pest control problems to the study of the environmental conditions under which pests could either be abundant or scarce so as to evaluate the factor or factors responsible (Hanna, 2009). Changes in regulations in the European Union (EU), North America and Japan have called for a reflection on crop protection practices in cocoa and other commodity crops (ICCO, 2007). 2 University of Ghana http://ugspace.ug.edu.gh For a correct and scientific solution of insect pest problems, it is of first importance to develop sound technique for the estimation of population as well as for quantitative measurement of factors governing population flactuation. Results from Owusu –Manu, (1971) who studied the population dynamics of S. singularis determined the least number of chemical application per mirid season and the best time to apply this rate. Adu acheampong et al. (2014), working on farmer‟s farms, came out with the population dynamics of mirids from five regions in Ghana. The current research focus on the relative abundance of the four species of mirids as well as other insect pests and the natural enemies of cocoa in three differently managed systems (Farmer‟s farms, Organic and CRIG Experimental managed cocoa farms). 1.1 Justification The current mirid control regime of spraying insecticides four times in the year between August and December was based on information on the peak periods of mirid attack, which usually coincided with the peak cropping season of Amelonado cocoa variety. With the introduction of the inter Amazon and other improved hybrids which produce pods throughout the year, the temporal and spatial distribution of mirids and other insects appear to have changed (Adu Acheampong et al., 2014). Moreover, changes in labour dynamics as a result of alternative livelihood, labour availability, cost of labour and changes in farm management have caused populations of mirids to increase (Adu Acheampong et al., 2014). 3 University of Ghana http://ugspace.ug.edu.gh There have been major shift from the use of organochlorine, organophosphate and carbamate insecticides (eg. Lindane,( gamaline 20), unden 200EC, Dursban 480) to the neonicotinoids (eg. Imidacloprid as confidor and thiamethoxam as Actara) and the synthetic pyrethroids (eg.bifenthrin as Akate master) and neem seed extract for organic products. The management and productivity of cocoa farms has been transformed over the last 20 to 30 years, largely through greater use of fertilizer and pesticides in order to increase yields ( The World Bank, 2011). As a basis for the correct timing and frequency of application of all available control methods, a study on the relative abundance of mirids and other insect pests on cocoa is therefore very necessary. 1.2 Objectives 1.2.1 Main objective To study the relative abundance of four species of mirids under three different managed systems. 1.2.2 Specific objectives 1. To study the relative abundance of four species of mirids in three differently managed systems. 2. To study the incidence of other insect pests in the three differently managed systems. 3. To study the incidence of natural enemies in the three differently managed systems. 4 University of Ghana http://ugspace.ug.edu.gh 4. Establish the relationship between the relative abundance of mirids and the incidence of the natural enemies on the three differently managed systems. 5. Determine the influence of specific climatic factors on the relative abundance of the dominant mirid species. 5 University of Ghana http://ugspace.ug.edu.gh CHAPTER TWO 2.0 LITERATURE REVIEW 2.1 Dynamism in insect pests control Before world war II, economic entomologists, in the absence of a potent weapon of defence against insects, had no option but to follow every possible approach to unravel any weak point in the life history of the pest which can lead to its effective control. Since the advent of DDT, BHC and organophosphorus insecticides some twenty years ago, economic entomologists found in their application the immediate answer to most of their problems ( Hanna, 2009). Overlooking the biological approach in insect control problems has led to the abuse of that valuable weapon which has been placed at our disposal. The stage has been reached that, when any pest appears attacking a crop, all that has to be done is to take a sprayer with DDT or any similar compound and treat the crop. At times elementary knowledge concerning the life history of the pest, which is so essential in guiding the entomologist to devise the control measures is completely lacking ( Hanna, 2009). Insects are powerful rapid adaptive organisms with high fecundity rate and short life cycle. Human interruption in agro-ecosystem and global climatic variations are disturbing the insect ecosystem. Erosion of natural habitats, urbanization, pollution and use of chemicals in agroecosystem manifold the intensity of environmental variations. Both abiotic (temperature, humidity, light) and biotic (host, vegetative biodiversity, crowding and diets) stresses significantly influence the insects and their population dynamics. In response to these factors insect may prolong their metamorphic stages, 6 University of Ghana http://ugspace.ug.edu.gh survival and rate of multiplication. Insect‟s immune responses as melanization, lysozyme level and phenoloxidase (PO) modify the physiology and morphological behavior against different factors like diets, gases and chemicals (khaliq et al., 2014). Global changes are responsible for wide range of anthropogenic and natural environmental Variation (Finlay-done and Walter, 2012). Climatic and weather changes affect insect pests population dynamics, distribution, abundance, intensity and feeding behavior (Ayres and Schneider, 2009). Intensity of change in climatic ecosystem noted by meteorological science has showed a direct and indirect effect on the prey and host relationship, their immune responses and rate of development, their fecundity and various physiological functions (Ayres and Schneider 2009). Abiotic disturbances particularly upper and lower thermal changes affect insect multiplication, diapauses, emergence, flight and the dispersal rate (Yamamura and Kiritani, 1998). Not only high temperature thresh hold is responsible for these variation but cool temperature play an important role in intrinsic properties of insect species (Regniere J.et al., 2012). In addition to abiotic factors, biotic changes are also equally responsible for the physiological, behavioral and morphological adaptations in the insects along with its population fluctuation ( Karl I. et al., 2011). Among biotic stresses of agro-ecosystem, terrestrial flora played most vital role in the development of various stages of terrestrial insects, their oviposition and hatching success (Lucas-Barbosa et al., 2011). In the years 1991, 1999, 2003 and 2012 Adu-Acheampong and others studied the temporal distribution of two important mirid species, Distantiella theobroma (Dist) and 7 University of Ghana http://ugspace.ug.edu.gh Sahlbergela singularis (Hgl) to determine the appropriate timing for the application of control measures in current farming systems. Mirid abundance on a total of 120 cocoa farms across six cocoa growing regions of Ghana; (Ashanti, Brong ahafo, Central, Eastern and Western regions) were sampled and measurement of mirid population dynamics made on a total of 23 farms during the 1999, 2003 and 2012 years. Because of the large variations between farms, they considered it unnecessary to compare data among the farms statistically. According to the report, there was high mirid population from January to April, dropping to low but constant levels until August. A second peak was recorded from October to November at most locations. An exception to this was in 1991, when a third peak was recorded in June. One of their recommendations at the end of the survey was that mass spraying is not all that necessary but there is the need for farmers to monitor the pest incidence before chemical application. Anikwe and others in 2010 also studied the population dynamics of the Brown cocoa mirid S. sigularis Hgl and its natural enemies. Mirid population and natural enemies abundance were correlated to monthly weather parameters (Temperature, Humidity and Rainfall). According to their result, the population of the pest rapidly build-up in August and this coincided with the main cropping season of cocoa where there are massive pod production. In 2008, Estay and others in Chile studied the population dynamics of two stored grain insect pests; Tribolium confusum and Callosobruchus chinesis. They concluded that, the 8 University of Ghana http://ugspace.ug.edu.gh results of the research will improve the communication with the general public and decision-makers which is a key aspect in integrated pest management. , Sana et al. (2009) studied the population dynamics of insects on cotton and their natural enemies. The experiment was conducted at the research farm of KPK Agricultural University, Peshawar, Pakistan. Density of insect pests such as Aphids, termites, Dyesdercus, Earias, Bollworm, cutworm, mites etc. and natural enemies such as S. invicta, C. septempunctata and Dictyna spp were recorded. The results showed that the population of the pests and their natural enemies peaked from June to October and they disappear completely after mid-October. 2.2 Theobroma cacao: origin and description Cocoa (Theobroma cacao) is one of 22 species of the genus Theobroma and from the family Sterculiaceae. It is a native of South America from where it has been introduced th to various part of the tropical forest belt since the 16 century (Kumar and Youdeowei, 1983). The species Theobroma cacao consist of a large number of highly morphological variable populations (Osei-Bonsu, 2005). Based on morphological traits and geographical origin, two main genetic groups had been defined within the species; Criollo and Forastero (Cheesman, 1944). The Criollo produces the most flavoursome cocoa but are difficult to establish and are also prone to attack by diseases and pests (Osei-Bonsu, 2005). The Forastero, which is produced widely in West Africa and 9 University of Ghana http://ugspace.ug.edu.gh constitutes the West Africa “Amelonado” is less flavoursome and can withstand disease and pest attack to compared to Criollo (Mossu, 1992). A third group, Trinitario is a hybrid of Criollo and Forastero. Their botanical features have all the intermediate features of Criollo and Forastero group (Mossu, 1992). Cocoa (Theobroma cacao) is cauliflorous or truncate, which means that the flowers develop on the older parts of the trunk and branches. Therefore, most of the fruits on the cocoa tree are developed around the trunk and to a lesser extent on older branches such as those forming the jorquette. The tree produces greenish white flowers at 1-5 years after planting in the field (Are, 1973). These flowers are produced seasonally from cushions that emerge on the bark of the trunk and stem (Thompson et al., 2001). A successfully pollinated flower produces pod. The development of the pod takes 5-6 month from pollination to ripening (Wood and Lass, 1985). When matured, the pods are dark green in colour and thin but firm in texture (Urquhart, 1961). The matured height of the tree is about 4-9m with a round canopy of 6-8m diameter if grown in isolation (Are, 1973). These fruits are called pods and contain 20–40 seeds (Urquhart, 1961; Are, 1973). The economic rotation for cocoa is estimated at 25 - 30 years, when yields may decline and replanting becomes necessary (Aranzazu, 1992). 10 University of Ghana http://ugspace.ug.edu.gh 2.2.1 Classification of cocoa Chessman (1944) classified cocoa into two major populations as follows: Criollo (native): Which include Central American Criollo and South American Criollo and Forastero (foreign): Which include Amazonian Forastero and Trinitorios. The Criollo Group: The Criollo populations are found cultivated in Mexico, Guatemala, Columbia, Venezuela, Madagascar, the Comoro Island, Sri Lanka, Indonesia and the Samoa Island (Mossu, 1992). They have pale pink staminodes and pods that are green or red before ripening, varying in shape, generally with very warty and thin pericarp and mesocarp that is only slightly woody and thin. The beans are round with white or very pigmented cotyledons. Criollo beans have strong aroma and are less bitter. They are, however, not very vigorous and are very vulnerable to the witches broom disease which occurs in Brazil (Mossu, 1992). The Forastero Group: The general name given to this type of cocoa is forastero (of the forest). The fruits are hardier than the Criollo type, grow stronger and yield more but have not so fine flavour. The Amazon Forastero: The fruit wall is hard and smooth on the surface. The beans are flat, deep violet in colour, and very bitter in taste and the resulting product is medium in quality. It is grown commonly in the Amazon basin (Brazil), in the Guyanas and along the Orinoco river in Venezuela, West Africa and South East Asia. 11 University of Ghana http://ugspace.ug.edu.gh The Upper Amazonian cocoa include the Forasteros collected during several expeditions from the Upper part of Amazon basin by many researchers. They bear the name of the place or the river in the region in which they have been traditionally harvested. These include Iquitos, Nanay, Paranari, Scavina, Morona, Moquique. Amelonado: This is the main and first cocoa type introduced into West Africa from Fernando Po by Tetteh Quashie (Are and Gwynne – Jones, 1974). It is a lower Amazonian Forastero coca. Most cocoa in West Africa is the Forastero type. The Amelonado cocoa of West Africa is a very homogenous population which can be distinguished from the newer Amazonian Forasteros that originated from the collecting expeditions since the later heterogeneous. 2.2.2 Cultivation of cocoa Cocoa is cultivated in the humid tropical belt (Motamayor et al., 2008). It requires a soil which can easily be penetrated by its roots, retain moisture during the dry season and permits the circulation of air and moisture (Urquhart, 1961). Good cocoa soils are deep well drained, non-gravelly top soil over a sandy clay loam layer with pH 8.5 and o o temperature maximum of 30-32 c and minimum of 18-21 C (Wood and Lass, 1985). The cocoa plant is highly susceptible to drought. In Ghana, cocoa cultivation is limited to the areas which receive not less than 250mm of rainfall from November to March (Adams and Mckelvie, 1955). The cocoa growing areas in Ghana are Ashanti, Brong Ahafo, Central, Eastern, Western and Volta regions (Manu and Tetteh, 1987). 12 University of Ghana http://ugspace.ug.edu.gh Cocoa, just as other widely grown perennials such as coffee (Coffea spp.), black pepper (Piper nigrum) and tea (Camellia sinensis) is grown under shade trees (Beer, 1987; Willson, 1999). In West Africa, cocoa farmers retain desirable trees to provide shade for young cocoa during clearing and land preparation (Oke and Odebiyi, 2008). Planting of cocoa is usually carried out from April to July during the rainy season. In Ghana, it is usually planted as nursery-raised polythene bag-type (Entwistle, 1972). When grown from seed, the cocoa tree fully develops at about 10 years; however, it is productive well before this age (Mossu, 1992). There are two main cocoa harvesting seasons in Ghana, the main and light crop season. The main crop season falls between September and February and the light crop season between March and August (Adzaho, 2007). 2.2.3 Cocoa producation in ghana There are many cocoa producing countries in the world but the major producers are from the African countries (Cote d‟Ivoire, Ghana, Nigeria, Cameroon), others major countries around the world include, Brazil, Ecuador, Papua New Guinea, Indonesia and Mexico (ICCO, 2011). World production of cocoa estimates rose from 3,593m tons in 2008/2009 cocoa season to 3,631m tones in 2009/2010 and 4,250m tones in 2010/2011 cocoa season (ICCO, 2011). Commercial production of cocoa in Ghana began when the cocoa pod was brought from Fernando Po by Tetteh Quarshie in 1897 (Hammond, 1962; Manu and Tetteh, 1987). In 13 University of Ghana http://ugspace.ug.edu.gh 1965/1966, cocoa production in Ghana reached an all-time peak of 560,000 tons but this fell to low of 150,000 tons in 1983/1984 season. This resulted in the country losing her position to Cote d‟Ivoire as the world largest producer of cocoa (Gill and Dutus, 1989). The ravages caused by insect pests and disease, low producer price, unavailability of production inputs such as insecticides, fungicides, fertilizer, spraying machines and labour, contributed to the dwindling of cocoa industry (Anon, 1995). In the 2010/2011 cocoa season, Ghana produced 1,024,150 tons, which was the highest production since Ghana registered its name in the international market as a producer of cocoa (Ghana Cocoa Board, 2011). Cocoa beans from Ghana are recognized because of their premium quality and therefore regarded as the world leader in premium quality cocoa beans (Ntiamoah and Afrane, 2008). 2.2.4 Economic importance of cocoa Cocoa is a main cash crop for several West African countries. It‟s a major source of income for many farmers in these countries (Motamayor et al., 2008). Cocoa is essentially important in areas where food security has been a problem (Belsky and Sibert, 2003). Since the introduction of cocoa into the country, the industry starting with rudimentary production technology, has made significant strides in major socio-economic contributions to date in such areas as employment, foreign exchange earnings, government revenue and gross domestic product (GDP). The cocoa industry in Ghana employs over 800,000 small holder farm families (Asamoah and Baah, 2003). Agriculture accounts for roughly one-quarter of G.D.P and employs more than half of the work force mainly small landholders (ISSER, 2014). 14 University of Ghana http://ugspace.ug.edu.gh The health benefits of cocoa cannot also be over emphasized. It helps to protect tissues against stress, and certain polyphenols work as preventive medicines for problems such as cardiovascular diseases, cancer, arthritis and autoimmune disorders. (Mursu et al., 2004) They act as antioxidants due to their free radical scavenging properties, their ability to reduce the formation of free radicals and their ability to stabilize membrane by decreasing membrane fluidity. (Aror et al., 2000 and Kromhout et al., 2002). Among botanical medicines, cocoa, ginkgo, elderberry and green tea are examples of rich sources of antioxidant polyphenols. (Lee et al., 2003). Some polyphenols (such as proanthocyanidins) exert beneficial cardiovascular effects through inhibition of platelet aggregation (Murphy et al., 2003). Other antioxidants found in cocoa beans include, catechins, epicatechin and procyanidins, polyphenols similar to those found in wine and tea (Carnesecchia et al., 2002; Hatano et al., 2002; and Hermann et al., 2006). 2.3 Cocoa insect pests Over 1,500 different species of insect pests have been recorded on cocoa but most of these have negligible effect on the plant (Mossu,1992). Important insect pests of cocoa worldwide include defoliators such as Adoretus lineola sp (Lepidoptera:Noctuidae); stem borers such as Tragocephala sp. (Coleoptera: cerambycidae); Zeuzera coffeae Nietn. (Lepidoptera : Cossidae), E. myrmeleon, Xyleborus sp. (Coleoptera: Scolytidae). Others are the pod borers Characoma 15 University of Ghana http://ugspace.ug.edu.gh stictograpta Hmps (Lepidoptera: Noctuidae); Ceratitis capitata (Wied) (Diptera: Tephritidae); the virus vectors Pseudococcus citri Risso (Homoptera: Pseudococcidae). Foliage feeders include Toxoptera aurantii B de F (Homoptera:Aphididae) and Tyora tessmani (Homoptera : Psylidae) ( Hill,1993). The insect pest complex that causes economic damage to cocoa in Ghana are the mirids or capsids (Heteroptera: Miridae), the mealybugs (Homoptera: Pseudococcidae) and, more recently the shieldbug, Bathycoelia thalassina (Heterptera: Pentatomidae), termites (Isoptera: Termitidae) and the stem borer, E. mymerleon (Lepidoptera: Cossoidae)(Hill, 1993). 2.3.1 Cocoa mirids The most widespread species in West Africa is S. singularis which is present from Sierra Leone to the Congo and in Fernando Po (known today as Bioko). D. theobroma attacks cocoa in Côte d‟Ivore, Ghana, Nigeria, but is rare in the Cameroon. Lavabre (1957) found it at Yaounde in the ratio of 1: 140 S. singularis is now the dominant species in Ghana (Padi and Adu-Acheampong, 2001). B. laticollis, perhaps synonyms with Brycoropsis cotterelli China in Bioko seems restricted to Ghana, Cote d‟Ivoire and Congo respectively . Odoniella reuteri (Hagl.) is known only from the Control (Entwistle and Youdeowei, 1964). To date, Caribbean cocoa-producing islands are free from mirid attack. On the other hand, more genera (Sahlbergella, Distantiella, Bryocoropsis, Odoneilla and Helopeltis ) 16 University of Ghana http://ugspace.ug.edu.gh attack cocoa in the Ethiopian and Madagascarene regions than elsewhere (Entwistle and Youdeowei, 1964). 2.3.2 Mirid damage D. theobroma was first noted in Ghana in 1909 and Nigeria in 1913 (Entwistle and Youdeowei, 1964). Young pods wilt or become severely distorted, cracked and with beans decayed but effects of feeding on mature pods are insignificant although attack by pathogenic fungi following attack on pods has often been reported for West Africa. Crowdy (1947) stated that in Gold Coast, fungus infected 80% of mirid lesions in the field. In Nigeria, 95% were infected (Anon, 1957). Crowdy (1947) concluded that the true position with regard to mirids attack is that neither the mirids nor the fungus alone normally does serious damage to the tree but, in combination. Their damage is one of the major problems facing the cocoa industry in West Africa. Mirid feeding may result in mirid blast where concentration of attack on branches leads to their death. The dead leaves turn brown, having withered, but remain on the branches for some time and this gives a characteristic scorched appearance. In Ghana blasting, occurs during the dry season i.e January – February. Feeding may also lead to the formation of mirid pockets which occur when the canopy of more or less discrete groups of tree is strongly degraded by intensive feeding on the branches. Two main phases of tree deterioration generally recognized are stag – headed trees and bare poles (Asante, 1997). 17 University of Ghana http://ugspace.ug.edu.gh Plate 1 : S. singularis feeding on cocoa 2.3.3 Ecology of cocoa mirids Factors which determine the distribution, occurrence and abundance of mirids include the presence or absence of alternative hosts, parasitoids and predators, the level of overhead shade, palatability of cocoa types and climatic conditions (Entwistle and Youdeowei,1964). Entwistle (1972) observed that a moderate rainy season was beneficial to mirids. 18 University of Ghana http://ugspace.ug.edu.gh In Ghana mirid attack usually begins when breaks occur in the tree canopy. S. singularis is usually the first coloniser due, according to Williams (1953), to its ability to feed better on fan branches than D. theobroma. The latter increase in numbers with regenerative chupon development. In Nigeria, cocoa is seldom shaded and mirid attack tends to be more diffuse, though pocket formation may result from breaks in the cocoa canopy itself. Mirid numbers fluctuate greatly during the year. Peak population of S. singularis and D. theobroma in Ghana and Nigeria occur from September to February with low populations from April to June. The factors affecting population change are little understood. In Ghana and Nigeria peaks of S. singularis and D. theobroma extend from the late rains into the dry season. Cotterell (1943) observed that number of S. singularis decreases rapidly in severe dry period and that 60% humidity is critical. 2.4 SHIELD/STINK BUG, Bathycoelia thalassina(HS.) (Hemiptera:Pentatomidae) B. thalassina also called “Atee” in the local language are large green insects which feed on cocoa pods. They lay their eggs on leaves, trunks and branches. Green pods fed on by B.thalassina adult and nymph stop growing, a condition known as “Immature Ripening”. They pierce the pod husk with their mouth parts and suck out the content of the beans. As a result young pods turn yellow and then black, large pods stop growing and becomes yellow. (Owusu Manu, 1975). The adult insect takes to wing when disturbed and during flight it produces a loud buzzing noise. Initially, both male and female insects would either fly in a spiral or a zig- zag formation for about 2 seconds and then go on a straight course. The normal period 19 University of Ghana http://ugspace.ug.edu.gh for newly emerged adult to fly was 3 days. Under field conditions, adult B. thalassina flew for short distances, from tree to tree but in an open field, it flew away over long distances and could not be seen again. Although there is some degree of dispersal in the larval stage, the bulk of dispersal occurs in the adult stage. Normally, when disturbed, the larvae drop to the ground and hide under cocoa litter. The second to fourth instar larvae behaved in a manner similar to that of fifth instars but the first instar larvae always climbed to the undersurface The loss due to this pest has been estimated as 18% of the total crop production (Owusu Manu, 1975). Plate 2 : B. thalassina on cocoa pod 2.5 Podborer, characoma stictigrapta hmps (lepidoptera: noctuidae) C. stictigrapta Hmps has in recent years become an important pest of cocoa in Ghana (Akotoye and Kumar, 1976) but little information is available on its biology and population dynamics. It is widely distributed in the tropics and in West Africa. In Ghana it has been found in the cocoa growing areas. It is able to colonize isolated cocoa stands. 20 University of Ghana http://ugspace.ug.edu.gh This moth is an active flyer and can transverse intervening vegetational zones to reach cocoa paches. However it can utilize other host plants such as kola and other Sterculiaceae (Akotoye and Kumar, 1976). C. stictigrapta is a grayish cryptic moth sometimes with a conspicuous discoid black spot situated dorsally and centrally on the forewings of both sexes. The female can live for about 11 days and the male for about 33 days. Adults mate 2 to 4 days after emergence with a preoviposition period of 5 to 6 days. The green eggs are laid singly at the rate of 15 to 18 per female in a 5 to 6 day oviposition period. They hatch 5 to 6 days later(larvae,11-12 days; pupae,12-14 days). The caterpillar is pinkish throughout its 5 intars (Akotoye and Kumar, 1976). The damage is done by the larva which bores holes into pods of all sizes. It produces a mass of frass held together by silk at the entrance of the holes. If the pod is very young and soft (cherelle) then it wilts. Plate 3 : C. stictigrapta larva damage to cocoa pods 21 University of Ghana http://ugspace.ug.edu.gh 2.6 The cocoa stem borer, Eulophonotus myrmeleon Most past information on the pest did not portray it as an important pest. (Cotterell,1928; Alibert, 1951). This is a moth. Losses from this insect are usually low but high numbers can seriously affect yield and tree health. Stem borers have been said to spread as a pest in cases of heavy pesticide abuse on trees, which kills off the natural predators of this pests. However from the late 1990s onwards, stem borers have become more noticeable, even on farms where no pesticides are used. A further problem is that stem borer entrance holes also serve as entry points for diseases such as Canker. Symptoms of the pest damage on cocoa include: presence of sticky sap on cocoa tree bark, branches lose their leaves, dry out and die off and presence of silk threads on branches. Rational use of pesticides example spot application helps to keep insect pests in check and to preserve natural enemies of stem borer. Barrier crops which are not attractive to stem borers such as sweet potato, cocoyam, leucaena sp. Could be planted to check their population (Awudzi et al., 2009). 2.7 Termites macrotermes spp( Isoptera: termitidae) Termites may live either in the canopy or in the underground. They attack seedlings or young trees at the base and without control, trees may wilt and die. This type of damage also happen to full-grown trees. In full-grown trees, some types of termites attack injured and dead wood. Other types chew into the roots and tunnel up into the branch. 12Termites can attack living cocoa wood. They chew the wood, which causes openings for diseases such as Canker. Symptom includes presence of mud tents on the trunk. 22 University of Ghana http://ugspace.ug.edu.gh Attack results in severe and sudden wilt of branches. They can be controlled by keeping trees undamaged to make them less attractive to termite attack. Spot application of botanicals such as neem rather than chemical pesticides (as chemical pesticide may kill the natural enemies of termites) are recommended ( Ackonor and Nkansah, 2001). Termites eat the roots and stems of cocoa and can cause death of plants. They cut down seedlings mostly in the dry season. Damage is common where dead decaying wood and leaves are gathered close to the base of stems. Their damage also causes leaves to wilt but remain hanging on plant ( Afreh-Nuamah, 1999). 2.8 Anomis leona Schauss and Earias biplaga WLK Anomis Leona and Earias biplaga belong to a group of insects called defoliators. The larvae (cater pillars) of the moths cause the damage. The A. Leona larva is green in colour with yellow markings on its sides whereas that of E. biplaga is black, hairy with white or brown patches on the body. The two species are common at the onset of the rains and all the five larval stages of both insects feed on tender leaves, creating a number of holes. They also feed on growing tips of the shoots and thereby delay the plant growth and canopy formation ( Awudzi et al., 2009). Their feeding activity prevents the plant from growing properly to form canopy. The attack is more where there is no shade over the cocoa. Their attack therefore may be prevented if fast growing shade trees are provided over cocoa that has been freshly planted ( Awudzi et al., 2009). 23 University of Ghana http://ugspace.ug.edu.gh Plate 4 : Anomis leona damage on cocoa leaves Plate 5 : Earias biplaga damage on cocoa leaves 24 University of Ghana http://ugspace.ug.edu.gh 2.9 Aphids (Toxoptera aurantii) and Psyllids Aphids are soft- bodied insects which suck sap from fresh succulent shoots and flowers . Infested flowers drop while development of infested seedling is retarded. Psyllids are also called jumping plant lice. Adults of both sexes are winged , feed on flowers and buds and thereby retard their growth. During drought periods, psyllids deposit large numbers of eggs in terminal buds resulting in desiccation and death of the bud and growth retardation in the shoots of young cocoa trees. Aphids and Psyllids are not showing any signs of serious pest. They may cause economic damage on unshaded matured cocoa. The insects are usually not controlled but serious outbreaks may be controlled on young Cocoa (Awudzi et al., 2009). 2.10 Mealybugs vector for CSSV. CSSV is primarily transmitted by mealybugs. Species within the family Pseudoccidae act as vectors for CSSV, but Planococcoides njalensis and Planococcus citri are the most important mealybug vectors (Belshaw and Bolton, 1993). Transmission is semi- persistent, meaning that the virus is taken up into the vector's circulatory system, but does not replicate within it. The feeding period required for acquisition of the virus is, at minimum 20 minutes, but optimally 2–4 days. Once acquired, the virus can be transmitted within 15 minutes, but optimal transmission occurs 2–10 hours after acquisition (Gibbs and Leston, 1970). No transmission of the virus occurs through the mealybug eggs. 25 University of Ghana http://ugspace.ug.edu.gh Light intensity has the effect of reducing swelling in shoots while plants in the shade show more severe symptoms. Temperature and nutrition have no significant effect (Ackonor, 1984).Since mealy bugs are the vectors of the virus, environmental conditions favorable to mealy bugs could increase the spread of the virus. Planococcus njalensis population density is closely correlated with density of ants in the Crematogaster genus, which build protective carton tents over the mealy bug colonies. High-density planting can facilitate the spread of the virus when mealy bugs are able to go from plant to plant through the interlocked canopy. Aside from crawling from plant to plant, mealy bugs can be dispersed by wind as well. In controlled trials, 340 feet was the maximum distance a mealy bug could be spread from an infected plant to a cacao seedling by wind dispersal. In dry conditions, aerial dispersal is increased (Dejean et al., 1993). Eradication of infected trees has been the most widely used means of control. In Ghana, between 2006 and 2010, over 28 million trees were removed for being visibly infected or for being in contact with infected trees. This serves to remove the source of inoculum to prevent spread of the virus; however the method has not succeeded to significantly control the disease. Since there are alternative host species that could also serve as inoculum, their removal has been advised too. Although it has been suggested that the importance of alternative hosts in cacao re-infection is not that great compared to cacao- cacao infection, it is still advised by Dzahini-Obiatey et al. (2005) that alternative hosts, such as Cola gigantea, be removed from newly planted fields. Before planting any new plantation, it is advised that all obviously infected trees in the surrounding plantations be removed beforehand. Also, a cordon, or gap, should be left 26 University of Ghana http://ugspace.ug.edu.gh around the entire plantation, putting the new plants a recommended 10 meters away from any old plantations that could possibly contain infected trees (Leston, 1972). It is also recommended that the cordon be planted with a CSSV-resistant crop to provide a physical barrier to the mealy bug vectors. This issue is being addressed by suggesting alternative cash crops such as citrus and oil palm, which have promise as barriers that prevent the spread of CSSV (Mckey, 1984). If only a single seedling is infected in a new plantation, it may seem insignificant at first. However, once the canopy starts to grow together with interlocking branches, mealy bug movement is facilitated and the virus can quickly spread to the whole plantation (Dejean et al., 1993). Planococcoides njalensis population density is closely correlated with density of ants in the Crematogaster genus, which build protective carton tents over the mealy bug colonies. Crematogaster populations however are negatively correlated with populations of ants of the Oecophylla genus. This could be a natural biological control that is worth considering if agents to control the Crematogaster ants are developed, since they should not target Oecophylla ants as well. 27 University of Ghana http://ugspace.ug.edu.gh Plate 6 : Planococcoides njalensis on cocoa pod 2.11 Beneficial fauna in cocoa ecosystem (ants mosaic) Ants have been described as the dominant social insects, both numerically and with regard to their wide distribution (Wilson, 1971). Individuals vary greatly in their food preferences (Carroll and Janzen, 1973; Petal, 1978): some obtain all or a large part of their food by predation, some subsist on seeds, while others rely on mutualistic relationships with plants (Janzen , 1966) and sap-sucking insects (Way, 1963). Leston (1970, 1973) and Majer (1972, 1976 a, b,c) working on cocoa, and Greenslade (1971) on coconut plantations, showed that the most numerous or dominant ants form a three- dimensional mosaic, and are associated with a distinctive fauna resulting from negative 28 University of Ghana http://ugspace.ug.edu.gh associations with group of insects which they prey upon and positive associations encouraging homopterans. Mutualism between ants and plant-feeding Homoptera is common. The ants obtain honeydew, a complex mixture of nutrients including free amino acids, amides, protein, minerals and B-vitamins, and ants play a diversity of roles in terrestrial ecosystems. Ants act as predators, scavengers, herbivores, detritivores, and granivores (Holldobler & Wilson 1990) and participate in an astonishing array of associations with plants and other insects (Beattie 1985, Holldobler & Wilson 1990). Ants, in turn, are preyed upon by a variety of specialist predators, including reptiles (Pianka & Parker 1975), mammals (Redford 1987), spiders (Porter & Eastmond 1982), and insects (Gotelli 1996) and are host to both dipteran (Feener & Brown1997) and hymenopteran parasitoids (Heraty 1994). Ants also serve as important agents of soil turnover, nutrient redistribution, and small-scale disturbance (Ho11dobler and Wilson 1990). For these reasons, and because they can be sampled and identified with relative ease, ants figure prominently in ecological studies and have become a key indicator group in studies of diversity and ecosystem function (Agosti et al., 2000). The widespread success of ants stems in large part from their elaborate social behavior, which is itself a tremendously rich source of information for studies of kin selection, reproductive skew, levels of selection, foraging behavior, and self-organization (Wilson 1971 and Holldobler & Wilson 1990). 29 University of Ghana http://ugspace.ug.edu.gh Oecophyla longinoda (weaver ant) are arboreal ants, living in heavily forested areas. The way in which weaver ants build their nests reduces spatial limitations to their colonies, and one colony may occupy several trees at one time (Holldobler and Wilson, 1994). There are four stages to the life cycle of weaver ants: Egg; Larvae; Pupae; Adult. It takes approximately 30 days to develop from an egg into an adult worker. There are also at least three larval instars (larval growth periods) before the immature ant can pupate. O. longinoda pupates without enclosing itself in silk, as it spends its silk on nest construction. Instead, it remains exposed as it undergoes a complete metamorphosis from its larval, grub-like form into an adult ant. (Holldobler and Wilson, 1994). After her nuptial (copulatory) flight, the new queen will find a protected area on the outer regions of a tree. She chooses the outer regions probably because other queens may have chosen the same tree and the farther away they are from each other the safer their brood are from the others' workers. The single queen is responsible for all the reproductive needs of the colony. She lays one hundred eggs per day, which are carried to brood piles to be cared for by the minor workers. (Tan, 2001). The African weaver ants are primarily insectivorous, attacking and eating any ants or other insects that invade their nest. They will even attack and eat weaver ants from other colonies. Another main staple food for the weaver ant is the honeydew excrement from herds of scale insects colonies often maintain. ( Holldobler and Wilson, 1994) African weaver ants can be used to protect cacao tree crops. Utilizing African weaver ants to control populations of these insects can greatly reduce crop damages due to this disease (Taylor, 1998) 30 University of Ghana http://ugspace.ug.edu.gh Promoting use of ants in pest management Important attributes of useful ant species (Finnegan, 1974) are listed by Risch and Carroll (Risch and Carroll, 1982 ) as follows: (a) they are very responsive to prey density; they can remain abundant even when prey is scarce because they can cannibalize their brood and, most importantly, use honeydew-producing Homoptera as a stable source of energy; (c) they can store food and hence continue to capture prey even if it is not immediately needed; (d) besides killing pests, they can deter many others including some too large to be successfully captured; (e) they can be managed to enhance their abundance, distribution, and contacts with prey. The stability, social organization, and foraging behavior of some predatory ants enable them to react quickly to increasing prey density, and also make them uniquely able to protect crops from pest. Predacious ants also affect other natural enemies, but less than might be expected, and may indeed benefits some. Ants tend to overlap the food niches of other predators and may force them into one competitive system. 2.12Recommended management practices in cocoa farms 2.12.1 Weed control Weeds are one of the greatest biological problems of cocoa farms. They compete with cocoa for water and nutrients thus hindering growth, performance and yield. Weed is more serious in young cocoa with unclosed canopy than in mature cocoa with closed canopy. The complete canopy suppresses weed growth though weed may become a 31 University of Ghana http://ugspace.ug.edu.gh problem in mature cocoa where canopy is damaged or where trees are missing due to death, poor establishment or dieback caused by mirids. Some weeds species are shade tolerance (example Axonopus compresus, Asystasia gigantica) and can even grow under a heavy cocoa canopy (Adeyemi, 1992). In some cases the young seedlings are completely smothered by weeds resulting in poor establishment (Adeyemi, 2000). 2.12.2 Pruning Pruning is a routine practice in cocoa and carried out to control the height of cocoa trees, to give the desired shape and ventilate farms to reduce disease and insect pest incidence. All unnecessary branches including chupons are removed. This allow for easy operation and movement in the farm. There are heavy and light pruning. Heavy pruning is carried out during the rainy season whilst light pruning is done anytime of the year. Normally all cut surfaces are painted to prevent entry of pathogens. Poorly maintained cocoa farms are often infested with parasites and epiphytes including Bryophytes, Liverworts, Mosses and Lichens. High levels of parasites and the others mentioned, result in the degeneration of cocoa trees, high incidence of disease and insect pest and consequently high yield loss (Adeyimi, 2000). 2.12.3 Shade management Cocoa requires shade only in the early establishment years when the root system has not fully developed and the trees are unable to absorb water from any depth of soil. Provision of shade reduces water loss from leaves as well as from the soil surfaces. Young cocoa trees experience stunted growth, chlorotic leaves and poor survival rate 32 University of Ghana http://ugspace.ug.edu.gh when grown under no shade condition (Are et al, 1971). Food crops and tree crops identified during the survey used for shading include: plantain, banana, cassava, pawpaw, citrus, oil palm, cola and bigger trees left on the farm during preparation of the farm. When the farm has been established, reduction of the shade is done gradually by killing the trees. Improve aeration from the reduction of shade leads to high yield because of reduced incidence of pests and diseases. Increased light intensity increases yield as dry matter accumulation in cocoa leaves increases as the light intensity increases (Omotoso@ , 1973). Shade is not necessary for mature cocoa as the roots are well developed and the canopy at this stage is closed enough to provide adequate shade to minimize moisture loss from the soil (Adeyemi, 2000). 2.12.4 Insect pests control Mirids and other insect pests infestation in cocoa farms is reduced by cultural practices and chemical control. The cultural operations involve the pruning of infested branches, regular removal of breeding sites and infested young cocoa pods to deprive the pest of suitable feeding and breeding sites. Good establishment of cocoa farms to form a closed canopy and preventing gaps through which the pests can enter the farm has always helped to minimize mirids and the other insect pests infestation (Adeyemi, 2000). Cocoa insect pests infestation has been historically controlled through the applications of contact insecticides such as Gammalin 20 EC, DDT, Dursban etc. Best results are obtained when applications are done in August, September, October, and December,(Owusu Manu, 1971). 33 University of Ghana http://ugspace.ug.edu.gh CHAPTER THREE 3.0 MATERIALS AND METHODS 3.1 Experimental material and period of the study The research was conducted between May 2013 to April 2014 in three differently managed cocoa farms; three Cocoa Research Institute of Ghana (CRIG) farms and three farmer‟s farmers farms located at Tafo and three organic cocoa farms at Akwadum, in the East Akim District and Suhum Kraboa Coaltar District respectively; all in the Eastern Region of Ghan The GPS coordinates for the study farms were as follows; CRIG farms 1(N 06° 13.729 W 000° 21.126 elevation 238 m), 2 (N 06° 13.810 W 000° 21.206 elevation 221 m) 3 (N 06° 113.866 W 000° 21.222 Elevation232 m); Farmers farms 1 (N 06° 13.394 W 000° 20.787 elevation 228 m), 2 (N 06° 13.373 W 000° 20.851 elevation 234 m), 3 (N 06° 13.328 W 000° 20.919 elevation 217 m) and Organic farms 1 (N 06° 05.544 W 000° 19.646 Elevation 186 m), 2 (N 06° 05.617 W 000° 19.657 Elevation 181 m) and 3 (N 06° 06.623 W 000° 20.947 Elevation174 m). 3.2 Characteristics of farms The research was conducted in a total of nine cocoa farms; three experimental plots 15 - 20 years old at Cocoa Research Institute, three farmer‟s farms 40 – 70 years old and three Organic farms 30 – 70 years old each of size 1 acre between May 2013 to April 2014. The organic farms were characterized by the use of bio-pesticides of plant origin (extracts of Azadiractin indica; neem and others on the market) to control the insect pests. The spraying pattern was mostly twice in the year, first in September and the second in 34 University of Ghana http://ugspace.ug.edu.gh March. Due to lack of effective pruning, there were at least three cocoa trees per stand. The farmers only clear weeds when they are about to harvest the ripe pods. The farms were intercrop with food crops, tree crops and trees such as plantain, banana, cocoyam, oil palm, citrus, kola, pear, tall trees for timber etc. in the organic farms. The farmer‟s farms were also intercrop with food crops, tree crops and trees. There was poor weed control and ineffective pruning. The farmers use inorganic insecticides such as Thiomethoxam (Actara) Imidacloprid (200 SL) (Confidor), Bifenthrin (Akate Master), etc twice in a year the first in September and the second spray in March. Whereas the organic farmers use Bio-pesticides (organic pesticides). Management practices in the CRIG farms showed a clear distinction compared to the first two systems. There were effective weed control and pruning. There were few big trees and insect pest were controlled with inorganic insecticides such as Thiomethoxam (Actara) Imidacloprid (200 SL) (Confidor), Bifenthrin (Akate Master), etc twice in a year the first in Septem. 35 University of Ghana http://ugspace.ug.edu.gh Fig. 3. 1 Map of Eastern Region showing Districts surveyed with dots 36 University of Ghana http://ugspace.ug.edu.gh 3.3 Sampling of mirids and other insects on cocoa One hundred (100) cocoa trees were randomly selected and tagged from each farm. Monthly records were made from visual counting of the insects from the base of the cocoa tree to the hand height (2m) of each of the tagged trees. The sampling was insect specific. The four mirid species (Sahlbergella, Distantiella, Helopeltis and Bryocoropsis), Bathycoelia, Characoma, Anomis, Earias, Eulophonotus and spider were counted individually but insects such as mealybugs, termites, Aphids, Psyllids, Camponotus, Crematogaster and Pheidole are social insects so the cocoa trees on which they were found were counted except in the case of Oecophylla where their nests on the cocoa trees were counted. 3.4 Statistical analysis Generalised linear models were used for data analysis. The data collected was square root transformed and Genstat statistical package was used to analyse the data. Analysis of variance was used to determine significance difference of mirids population in the different managed farms. Questionnair administration Owners of the cocoa farms were interviewed. The interview was based on one - on - one questionnaire for information on the following: name of farmer, age, sex, farm size, farming practices, cocoa varieties, age of the farm, pesticides use pattern, application of the insecticides and the frequency of application of the insecticides. 37 University of Ghana http://ugspace.ug.edu.gh CHAPTER FOUR 4.0 RESULTS 4.2 Mirids population The populations of the four species of mirids in the three systems have been summarized in Fig. 4.1. A total of six hundred and forty six (646) mirids were sampled during the study period. D. theobroma was completely absent in all the three different systems. There were five hundred and fifty four (554) S. singularis individuals, accounted for 85.78% of the total sample, eighty five (85) Helopeltis formed 13.16% and seven (7) B. laticollis accounted for only 1.08% of the total sample. The mirids rapidly built up in between August to September coinciding with the major fruit bearing time of cocoa trees. There was a drop of the mirids populations in November in all the systems. This was observed to be associated with the peak harvesting period. During this period there was a reduction in the number of pods and site where mirids fed and reproduce. 38 University of Ghana http://ugspace.ug.edu.gh 250 200 150 100 ORGANIC CRIG 50 NON-ORGANIC 0 Species of Mirids Fig. 4.1 Total population of the four species of mirids in the three systems. 4.2.1 Trend of s. singularis populations in the three sytems compared. Fig. 4.2 shows the trend of Sahlbergella populations in the three systems. Both Organic and farmer‟s recorded the highest Sahlbergella numbers in September with peak populations of ninety nine (99) and fifty (50) respectively. Except in CRIG farms where it occurred in March with a peak population of fifty eight (58). The farmer‟s had three peaks, first in June but dropped sharply until September where the peak was highest and dropping low again until February where the third peak occurred. Organic had two peaks with the first occurring in July but dropped sharply until September where the highest peak was recorded. 39 Population of mirids species per 300 cocoa trees per month University of Ghana http://ugspace.ug.edu.gh There was very low population of Sahlbergella at CRIG from May 2013 to January 2014 but increased drastically in March recording the highest peak. 40 University of Ghana http://ugspace.ug.edu.gh 120 100 80 60 ORGANIC CRIG 40 NON-ORGANIC 20 0 MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR Months Fig. 4.2 Trend of S. singularis populations in the three systems. 4.3 Other insect pests of cocoa population studies The population of Bathycoelia in the three systems have been summarised in Fig.4.3. There was a total of fifty one (51) Bathycoelia thalasina individuals in all the nine farms (three farms in each system). The farmer‟s farms recorded the highest population of twenty eight (28) representing 54.90%. The populations at CRIG and Organic farms were seventeen (17) and six (6) representing 33.33% and 11.76% of the total sample respectively. 41 Population of S.singularis per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh BATHYCOELIA 30 25 20 15 10 5 0 ORGANIC CRIG NON-ORGANIC Sytems Fig.4.3: Population of Bathycoelia thalasina in the three systems. In the organic farms Bathycoelia was present in only four months and with very low population numbers (March- 2, April- 1, July- 2 and November- 1). The insects were found in five months at CRIG (February- 5, March- 1, May- 3, June- 7 and July- 1). The inorganic farms recorded the highest incidence of the insects and were found in seven months (March- 6, April- 2, May- 2, June- 4, July- 9, August- 4 and October- 1) (Fig. 42 Population of Bathycoelia per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh 4.4). 10 9 8 7 6 5 ORGANIC 4 CRIG 3 NON-ORGANIC 2 1 0 MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR Months Fig. 4.4: Trend of Bathycoelia population in the three systems From the survey it was observed that one cocoa tree may have as many as eight (8) cherelles prematurely ripened with only one Bathycoelia present or sometimes the insect may be absent. The organic farms recorded Bathycoelia pod damages throughout the period except the first three months of the survey (May, June and July) with Sept recording the highest numbers. The numbers of damaged pods recorded in each month in the organic farms are: Aug- 24, Sept- 50, Oct- 7, Nov- 8, Dec- 3, Jan- 4, Feb- 8, Mar- 14, Apr- 5. The numbers of pod damages by Bathycoelia found in the CRIG farms were not as many as that of the other two systems. Again there were no records in the first three months of the survey and one other month (May, Jun, Jul and Nov) with Oct recording the highest numbers. The numbers of pod damages recorded at CRIG are as follows 43 Population of Bathycoelia per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh Aug- 1, Sept- 4, Oct- 11, Dec- 3, Jan- 3, Feb- 8, Mar- 5, Apr- 3. The numbers of Bathycoelia damages were highest in the inorganic farms and apart from July there were records of the insect damages in each month throughout the period with Sept recording the highest numbers of 45 premature ripened pods (Fig. 4.5). 60 50 40 30 ORGANIC CRIG 20 NON-ORGANIC 10 0 Months Fig. 4.5: Trend of Bathycoelia damage pods in the three systems Fig.4.6 shows the population of Characoma in the three systems. Out of the one hundred and forty one (141) Characoma individuals sampled, the Organic farms recorded the highest population of fifty seven (57) representing 40.43%. The farmer‟s farm and CRIG recorded fifty five (55) and twenty nine (29) representing 39.00% and 20.57% of the total sample respectively. 44 No. of pods damaged by Bathycoelia per 300 cocoa trees MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR University of Ghana http://ugspace.ug.edu.gh CHARACOMA 60 50 40 30 20 10 0 ORGANIC CRIG NON-ORGANIC Systems Fig.4.6: Population of Characoma in the three systems The study revealed that the insect population was highest in the months of August, November and December and lowest in March in the organic farms with numbers 7, 7, 7 and 2 out of 300 cocoa trees in each month respectively. In CRIG, the population of the insect was 6 in March which was the highest and the insect was absent in September and November. The highest number of 9 was recorded in February with May recording the lowest number of 1 in the inorganic farms. The insect was present throughout the period for both the organic and the inorganic systems. Fig. 4.7 shows the trend of Characoma population in each month. 45 Population of Characoma per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh 20 18 16 14 12 10 ORGANIC 8 6 CRIG 4 NON-ORGANIC 2 0 Months Fig. 4.7: Trend of Characoma incidence in the three systems Fig.4.8 shows the population of Eulophonotus in the three systems. A total of sixteen (16) Eulophonotus individuals were recorded during the period. There were eight (8) (50%) in the farmer‟s farm, six (6) (37.50%) in the Organic farms and two (2) (12.50%) in the CRIG farms 46 Population of Characoma per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh EULOPHONOTUS 12 10 8 6 4 2 0 ORGANIC CRIG NON-ORGANIC Systems Fig. 4.8: Population of Eulophonotus in the three systems. .Fig.4.9 shows the population of Anomis in the three systems. Out of the twelve (12) Anomis individuals recorded, there were six (6) (50.00%) in the CRIG farms, four (4) (33.35%) in the Organic farms and two (2) (16.67%) was found in the non-ogarnic farms 47 Population of Eulophonotus per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh ANOMIS 6 5 4 3 2 1 0 ORGANIC CRIG NON-ORGANIC Systems Fig.4.9 Population of Anomis leona in the three systems. The population of Earias in the three systems have been summarized in Fig. 4.10. Only three (3) Earias individuals were recorded in the Organic farms. The pest was absent in both the CRIG and the farmer‟s farms. 48 Population of Anomis per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh EARIAS 3 2.5 2 1.5 1 0.5 0 ORGANIC CRIG NON-ORGANIC Systems Fig.4.10: Population of Earias biplaga in the three systems Fig. 4.11 shows the number of cocoa trees with termites in the three systems. Out of the nine hundred (900) cocoa trees sampled, the insect were found on twenty six (26) cocoa trees (45.61%) in the farmer‟s farms. Organic farms recorded sixteen (16) cocoa trees (28.07%) and only fifteen (15) cocoa trees (26.31%) at CRIG had the insect. 49 Population of Earias per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh TERMITE 30 25 20 15 10 5 0 ORGANIC CRIG NON-ORGANIC Sytems Fig.4.11: Population of Termites in the three systems Fig.4.12 shows the number of cocoa trees with mealybugs in the three systems. Trees with either njalensis or citri were counted together. Out of the nine hundred (900) cocoa trees, two hundred and fifty six (256) cocoa trees had the insects. They were mostly found on the pods, between the stem and the pod, on the pod stalk and on the chupons of the cocoa trees. The Organic farm recorded the highest number of one hundred and twenty four (124) (48.44%) cocoa trees with the insects. The farmer‟s farms had ninety four (94) (36.72%) and in the CRIG farms thirty eight (38) (14.84%) cocoa trees with mealy bugs were found. 50 Number of cocoa trees with termites per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh MEALYBUGS 140 120 100 80 60 40 20 0 ORGANIC CRIG NON-ORGANIC Systems Fig.4.12: Number of cocoa trees with Mealybugs in the three systems. Trees with either njalensis or citri were counted together. The highest numbers of 18 cocoa trees having the mealybugs were recorded in December and the lowest numbers of 4 trees were recorded in February for the organic farms. CRIG recorded the highest numbers of 7 of trees with the insects in May and a single tree with mealybugs were recorded in November, January, Febuary, March and April. The highest numbers of 14 cocoa trees with mealybugs were recorded in June and the lowest numbers of 3 trees in April were found in the inorganic farms (Fig. 4.13). 51 Number of cocoa trees with mealybugs per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh 20 18 16 14 12 10 ORGANIC 8 CRIG 6 NON-ORGANIC 4 2 0 MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR Months Fig. 4.13: Trend of mealybug incidence in the three systems The number of cocoa trees having Aphids and Psyllids on them have been summarized in Figs.4.14 and 4.15. The results obtained show that psyllids were more dominant in all the three systems than aphids. CRIG farms recorded the highest population of fifty (50) cocoa trees out of three hundred trees with psyllids. The farmer‟s and organic farms had thirty eight (38) and twenty two (22) cocoa trees with psyllids respectively. In general, the population of aphids was low. The CRIG plots recorded the highest number of ten (10) cocoa trees with aphids. Six (6) cocoa trees were found having the insect in the organic while five (5) cocoa trees in the farmer‟s farms were having aphids on them. 52 No. of cocoa trees with mealybugs per 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh APHIDS 10 8 6 4 2 0 ORGANIC CRIG NON-ORGANIC Systems Fig. 4.14: Number of cocoa trees with Aphids in the three systems PSYLLIDS 50 40 30 20 10 0 ORGANIC CRIG NON-ORGANIC Systems Fig.4.15: Number of cocoa trees with Psyllids in the three systems 53 Number of cocoa trees with Number of cocoa trees with Aphids per Psyllids per 300 cocoa trees 300 cocoa trees University of Ghana http://ugspace.ug.edu.gh 4.4 Natural enemies temporal distribution Table 4.3 below shows the numbers of Oecophylla nests, numbers of trees with Camponotus, Crematogaster, Pheidole and the population of spider in the three systems. There were eight hundred and forty six (846) Oecophylla nests counted during the survey. The farmer‟s farms had the highest number of four hundred and fifty seven (457) (54.02%) nests with CRIG farms recording one hundred and ninety six (196) (23.18%) nests. The Organic farms recorded the least with one hundred and ninety three (193) (22.81%) nests. Out of the nine hundred (900) cocoa trees, five hundred and seventy six (576) were having Camponotus on them. CRIG farms recorded the highest with two hundred and ten (210) (36.46%) cocoa trees having the insects. The farmer‟s farms recorded one hundred and eighty six (186) (32.29%) and one hundred and eighty (180) (31.25%) cocoa trees were found in the Organic farms having the insect on them. Crematogaster were found on one hundred and thirty six (136) cocoa trees. The Organic farms recorded the highest number of eighty (80) cocoa trees having the insects representing 58.82% of the total sample. The farmer‟s farms and CRIG farms had thirty eight (38) (27.94%) and eighteen 18 (13.24%) of cocoa trees having the insects respectively. Out of the nine hundred (900) cocoa trees sampled, Pheidole were found on three hundred and thirty eight (338) trees. Organic farm recorded two hundred and sixteen (216) (63.90%) cocoa trees with the insects, farmer‟s farms had sixty six (66) (19.53%) 54 University of Ghana http://ugspace.ug.edu.gh trees having the insects and fifty six (56) (16.57%) cocoa trees were found in the CRIG farms with the insects. Only eighteen (18) spiders were found on the nine hundred (900) cocoa trees sampled. The arthropods were counted individually. Ten (10) (55.55%) spiders were found in the organic farms, 5 (27.78%) in CRIG farms and 3 (16.67%) were in the farmer‟s farms. TABLE 4.1: Populations of natural enemies Total population Insect species Organic crig farmer’s O. longinoda (T) 193 196 457 Camponotus (T) 180 210 186 Crematogaster (T) 80 18 38 Pheidole (T) 216 66 56 Spider (T) 10 5 3 55 University of Ghana http://ugspace.ug.edu.gh 4.5 Mirids population compared to the climatic factors (rainfall, temperature and relative humidity) The influences of climatic factors on the population of S. singularis are summarized in figures 4.19 – 4.27. The peak relative humidity occurred in August with value of 86.7%. Second instar nymphs of S. singularis have been reported to thrive better at very high humidity and tend to desiccate at very low humidity (Entwistle P.F,1972). The gradual decline in the population of mirid in December was in consonance with the drop in the relative humidity of 77.2%. Maximum rainfall was recorded in the month of July and the minimum rainfall was recorded in August with values 231.4mm and 4.4mm respectively. The least mean monthly temperature of 28.5C was recorded in July and August while the highest temperature of 33.4oC was recorded in both February and March. 250 200 150 Rainfall 100 Temp. Humidity 50 0 MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR Month Fig.4.16 Mean monthly climatic conditions during the study period. (Source: CRIG Meteorological Department) 56 Mean of climatic conditions University of Ghana http://ugspace.ug.edu.gh Influence of rainfall on the population of S. singularis 120 250 100 200 80 150 60 100 Sahlbegerlla 40 Rainfall 20 50 0 0 Months Fig.4.17: Influence of Rainfall on Sahlbergella population in the organic system 70 250 60 200 50 40 150 30 100 Sahlberbella 20 50 Rainfall 10 0 0 Months Fig.4.18: Influence of Rainfall on Sahlbergella population in the CRIG system 57 Population of Sahlbergella Population of Sahlbergella in the in the CRIG System organic system Mean monthly Rainfall Mean monthly rainfall University of Ghana http://ugspace.ug.edu.gh 60 250 50 200 40 150 30 100 20 Sahlbergella 10 50 Rainfall 0 0 Months Fig.4.19 Influence of Rainfall on Sahlbergella population in the farmer’s system Influence of temperature on the population of S. singularis 120 34 33 100 32 80 31 60 30 29 Sahlbegerlla 40 28 Temperature 20 27 0 26 Months Fig.4.20: Influence of Temperature on Sahlbergella population in the organic system 58 Population of Sahlbergella in Population of Sahlbergella the organic system in the non-organic system Mean monthly Temperature Mean monthly Rainfall University of Ghana http://ugspace.ug.edu.gh 70 34 60 33 50 32 31 40 30 30 29 Sahlberbella 20 28 Temperature 10 27 0 26 Months Fig.4.21: Influence of Temperature on Sahlbergella population in the CRIG system 60 34 33 50 32 40 31 30 30 29 Sahlbergella 20 28 Temperature 10 27 0 26 Months Fig.4.22: Influence of Temperature on Sahlbergela in the farmer’s farm 59 Population of Sahlbergella in Population of Sahlbergella in the non-organic system the CRIG system Mean monthly Temperature Mean monthly Temperature University of Ghana http://ugspace.ug.edu.gh Influence of Relative Humidity on the population of S. singularis 120 88 86 100 84 80 82 80 60 Sahlbegerlla 78 40 76 Humidity 74 20 72 0 70 MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR Months Fig.4.23: Influence of R. Humidity on Sahlbergella in the organic system 70 88 60 86 84 50 82 40 80 30 78 Sahlberbella 76 20 74 Humidity 10 72 0 70 Months Fig. 4.24: Influence of R. Humidity on Sahlbergella in the CRIG system. 60 Population of Sahlbergella in Population of Sahlbergella in the CRIG system the organic system Mean monthly R. Humidity Mean monthly R. Humidity University of Ghana http://ugspace.ug.edu.gh 60 88 86 50 84 40 82 80 30 78 Sahlbergella 20 76 Humidity 74 10 72 0 70 Months Fig.4.25: Influence of R. Humidity on Sahlbergella population in the farmer’s system. 4.6 comparison of mean S. singularis population in the three systems Analysis of variance showed that there was no significant difference in the number of S. singularis population in the three systems. (Anova: F. pr = 0.925; p > 0.05 Results from the interview showed that the organic cocoa farmers do not use inorganic insecticides in controlling insect pests on cocoa as being used in the farmer‟s and CRIG farms. They use bio-pesticides such as neemasol (axtract from Azardiractin indica) and other available organic insecticides on the market. In order to promote the adoption of the organic system, CRIG and other organic cocoa buying companies provide some forms of incentives to the farmers. CRIG gave the farmers some money at the end of the two main harvesting seasons and the buying companies provided the bio-pesticides to spray their farms twice in the year (September and March) through the chairman of the organic cocoa farmers union. 61 Population of Sahlbergella in the non-organic system Mean monthly R. Humidity University of Ghana http://ugspace.ug.edu.gh CHAPTER FIVE 5.0 DISCUSSION 5.1 Management practices in the three systems Weed control was not effective in the organic farms. The only time the farmers cleared the weeds in their farms was when they were about to harvest the ripe pods these were between September and November and around February and March each year. The presence of weeds most of the time in the organic farms could be the reason for the high populations of mirids and the other insect pests as compared to the insect pests population in the CRIG farms which were always free from weeds. This confirms Adeyemi (2000)‟s findings that weeds serve as reservouir for diseases, insect pest and other rodents that devour cocoa pods. Some common weeds species identified in the course of the study were Chromolaena odorata, panicum spp. etc. The organic farmers hardly pruned their farms. Interacting with the farmers revealed that, they expected the extra chupons to turn to trees which will bear more cocoa pods. It was observed that, more than half of the cocoa trees sampled were made up of more than three cocoa trees per stand. The worse was the „replicate 2” of the organic farms which recorded an average of four cocoa trees per stand. Since proper farm sanitation through pruning and weeding allows ventilation and the removal of breeding sites for insect pests and pathogen (Adeyemi, 2000), this could have accounted for the high population of mirids and other insect pest in the organic systems. From the study cocoa farms with canopies recorded low numbers of the insect pests but those with both the cocoa trees canopy and overhead canopy by bigger trees had very few numbers of cocoa pods with subsequent low population of the insect pests. The first two 62 University of Ghana http://ugspace.ug.edu.gh organic farms were covered with thick overhead canopies from the interlocking branches of a lot of big trees left on the farms creating heavy shade reducing visibility even during the day. Although because of very few pods available all the time the total number of mirids recorded were less than 10 for the whole period but with drastically low yield compared to the other eight cocoa farms. The farm owner was advised on the importance of effective shade management at the end of the survey. Some of the trees identified were Terminalia superba, Ceiba pentandra, Khaya senegalensis etc. Apart from the organic farmers using bio-pesticides in controlling insect pest and inorganic insecticides on the farmer‟s farms, the rest of the management practices identified during the survey were almost the same as the organic system. Weed control was poor and they also cleared the weeds when they were about to harvest the ripe pods between September and November and around February and March each year. The high populations of mirids and the other insect pests could be due to poor weed control. 63 University of Ghana http://ugspace.ug.edu.gh The effective shade management at CRIG farms led to more cocoa pods and low levels of the insect pest population most of the time compared to the Organic and the farmer‟s farms. The low numbers of mirids and other insect pest population recorded in the CRIG cocoa farms could be due to the effective pruning. It was observed even in our last survey that the workers at CRIG pruned from the base of the cocoa trees up to the branches using ladder and removing plant parasites such as mistletoe and epiphytes found on both the stem and the branches. Workers at CRIG also used inorganic insecticides such as Thiomethoxam (Actara) Imidacloprid (200 SL) (Confidor), Bifenthrin (Akate Master) etc. in controlling insect pests twice in the year (September and March) in the institution farms. In addition fungicides such as Metalaxyl-M + Copper (1) oxide (Ridomil Gold WP), Copper hydroxide (Koside 2000 DF), Cupric hydroxide (Champion WP), Copper hydroxide and metalaxy (Fungikill 50 WP) were also sprayed specifically on the cocoa pods to prevent fungal infections in the lesions created by the mirids as well as black pod disease also caused by fungus. The general low numbers of mirid population recorded in the CRIG farms compared to the pest population in the organic and the farmers farms could be due to the regular weed control, effective pruning and regular application of insecticides. 5.2 Mirids population and trend in the three systems The results of the survey in terms of species dominance revealed that S. singularis was the most dominant species in all the three systems. The second economic important 64 University of Ghana http://ugspace.ug.edu.gh mirids species D. theobroma was absent in all the nine farms but a recent publication by Adu Acheampong et al. (2014) reported of a reasonable percentage of D. theobroma species in their study. Their study covered a wider area and more number of cocoa farms ( six regions in Ghana and the population of the pests were studied in 102 cocoa farms) as compared to 9 farms in only Eastern region. Helopeltis species was also found in all the three systems but with much lower population densities compared to the densities of S. sigularis. The forth species, B. laticollis was absent in both the Organic and farmers farms. It was only found in the CRIG farms. Economically, damages caused by Helopeltis and Bryocoropsis are not as severe as damages of S. singularis and D. theobroma if present. The population of mirids in the three systems revealed that mirids population build up coincided with increase in the number of pods in the field. This correlation was corroborated with the report of Adu Acheampong that higher population of mirids was positively pods related (length of time that trees carry pods). The mirids population was highest in September for both the organic and the farmer‟s farms. The reason being that, pod numbers on trees were highest during this period. Williams (1953) showed that mirids preferred to hide under pods, especially the immature stages. CRIG farms recorded very low mirids population from May to January but rose suddenly from February to April with the highest peak in March. The trend may be as a result of effective control of the insects before the major harvesting season in November. The drastic increase in the mirids population in March could be due to ignorance on the part of the workers in monitoring the pest incidence. 65 University of Ghana http://ugspace.ug.edu.gh Critically, the result of the trend of mirids population in the farmers farm showed three peaks (September, March and June), an exception from the two peaks most researchers have reported. This is a confirmation of what Adu Acheampong et al reported in their four year study of the temporal distribution of D. theobroma and S. sahlbergella. According to the report they recorded three peaks in 1991 where the third peak also occurred in June. The results obtained clearly indicate that the mirids were scarce in very old cocoa farms. The total population of mirids recorded in farms 1and 2 in the Organic farms was 44 and the population of mirids in the third Organic farm was 141, more than 3 times. The ages of the first two farms was more than 70 years and were made of Amelonado cocoa variety whilst the age of the third farm was less than 30 years and were made of the Hybrid variety. This corroborated with the report of Adu Acheampong et al. (2014) that mirids preferred pods and basal shoots for shelter, oviposition and food, this explains why the pest was abundant on newer varieties and cocoa farms less than 30 years old. Although, there were differences in the populations of the mirids in the three systems, because of the large variations between the farms some researchers consider it unnecessary to compare the data among the farms statistically (Adu Acheampong et al., 2014). 66 University of Ghana http://ugspace.ug.edu.gh 5.3 Other insect pests on cocoa sampled The relative abundance of other insect pests on cocoa were also studied. In all, 9 insect pests apart from the 4 species of mirids were studied. These were Bathycoelia, Characoma, stem borers, Anomis, Earias, Mealy bugs, Termites, Aphids and Psyllids. From the results obtained the population of B. thalassina in the farmers farm was on a higher side as compared to the other two systems. The population of the insect was high from March to July with the highest peaks occurring in July, June and March in the farmers, CRIG and Organic farms respectively. Formally the insect was not considered a major pest until it was declared so at the forth conference of west African Cocoa Entomologists held in Ghana in 1974 (Owusu Manu, 1971). It was observed in the survey that, over 8 cocoa cherelles (small pods) could be seen prematurely ripped (yellowing) on one cocoa tree as result of the feedind habit of the insect. From observation, the numbers of Bathycoelia damages recoded was so great compared to the numbers of the individual insect counted. This shows that one or two of the insect found on one acre cocoa farm can cause serious damages that may be of economic importance. The insect pest may become more serious pest and compete with mirids in terms of percentage damage if control measures were not seriously taken. This observation confirms the report by Owusu Manu that Bathycoelia was becoming an important pest of cocoa in most of the cocoa growing areas in West Africa (Owusu Manu, 1971). 67 University of Ghana http://ugspace.ug.edu.gh From the study, population of Characoma was dominant in both the farmers and Organic farms with very small difference between the populations in the two systems. CRIG recorded the lowest population of the insect. The pest was present almost throughout the year with higher populations occurring in the drier months, from August to December. This confirms the report by Joseph Anikwe et al. that more pods were damaged in Novermber 2008 and 2010 and December 2009 and least damage on pods was recorded in June 2008, 2009 and May 2010 (Anikwe et al., 2012). Characoma is a moth whose larva is the destructive stage, boring into pods and producing a mass of frass. CRIG, (2009), reported that, damage by the insect to mature pods did not affect the beans since it was only on the pod surface, but young pods (cherelles) could wilt and die if attacked by the insect ( Awusdzi et al., 2009). The results also confirms report by Akotoye and Kumar (1976) that Characoma had become an important pest of Cocoa in Ghana. Eulophonotus myrmeleon Fldr is a moth whose larva causes the damage. Losses from this insect are usually low but a high numbers could seriously affect yield and tree health. The population of the cocoa pod borer (Eulophotus myrmeleon Fldr) in general was low in all the three systems. The highest incidence of the pest was found in the farmer‟s farms with CRIG farms having the lowest. From the results, the insect was present from May to September and not even a single one was recorded from October to February in all the systems. This confirms the report by Anikwe (2010) that the pest incidence increased during the rainy season with very low pest incidence occurring during the dry season. Anon (1995) observed that the damage caused by stem borers was becoming increasingly important in the whole country and recomended that CRIG should intensify research for a quick solution to this problem. 68 University of Ghana http://ugspace.ug.edu.gh CRIG farms recorded the highest with only 6 for Anomis nothing for Earias. The organic had 4 anomis and 3 was recorded for Earias and lastly the farmers farms recorded 2 and 0 for Anomis and Earias respectively. The results showed very low incidence of the pests in all the nine farms. This could be attributed to the old age of the cocoa farms. The few of the insects recorded were found on the leaves of the chupons. This clearly shows that, the insects may completely be absent if proper pruning practices were done. This confirms the work of Entwistle who said that, they were insect pests which were particularly important on young cocoa and caused the tip burn disease ( Entwistle, 1972). Mealybugs were present in all the nine farms almost all the months during the study. The organic farm recorded the highest population with CRIG having the least. From the observation, njalensis was very common as compared to the citri. Again the colonies of njalensis were much larger than that of the citri. It was observed that, different species of ants such as Phiedole, Crematogaster etc were attending to the mealybugs. This confirms the report by Awudzi et al., (2009) that a strong mutual beneficial association exists between ants and mealybugs. The ants feed on the sugary sap (honey dew), containing amino acids, which is excreted by the mealybugs. In return, ants carry mealy bugs from tree to tree (disperse them) and protect them from some natural enemies. The study revealed that, the population of mealybugs were high between May and August in all the three systems. The result of the study showed clearly that, very low incidence of termites were recorded in all the three systems. No significant termite related cocoa tree death was identified in the nine farms but only run ways with the insects on the stem of some few cocoa trees 69 University of Ghana http://ugspace.ug.edu.gh were found with no serious damages. The results could be due to the age of the farms where they were all more than 10 years. This confirms the report by Awudzi et al. (2009) that termites are usually underground pests whose presence can be detected, especially during the dry season (November to April), by their run ways along healthy – looking stems. The insect attacks nursery cocoa (seedlings) at ground level by eating the woody portions. Termite damage to seedlings causes the leaves to wilt but remain attached to the plant, eventually killing it. The population of psyllids far outnumbered that of aphids in the three systems. No serious damage caused by the two insects was identified during the period. The reason could be due to the old ages of the cocoa farms selected. This corroborates with the work of Awudzi et al. (2009) that Aphids are soft – bodied insects which suck sap from fresh, succulent shoots and flowers. Infested flowers dropped while development of infested seedlings was retarded and psyllids deposited large numbers of eggs in terminal buds resulting in desiccation and death of the bud and growth retardation in the shoots of young cocoa trees. Serious economic damage to cocoa by aphids and psyllids was rare. 5.4 Natural enemies populations The ant species identified in the survey include: Oecophylla longinoda, Camponotus, Crematogaster and phiedole. O. longinoda was dominant in the farmers farms, Camponotus dominated in the CRIG farms and both Crematogaster and Phiedole were also dominant in the organic farms. 70 University of Ghana http://ugspace.ug.edu.gh It was observed that cocoa farms with high populations of the ant species recorded very low numbers of the mirids. Taking the first two cocoa farms in the farmer‟s system into consideration, farm one recorded low numbers of Oecophylla nests with high population of S. sigularis, farm two recorded about three times Oecophilla nests compared to nest recorded in farm one with very few S. sigularis individuals recorded. The trend was the same in all the nine farms;” the higher the population of Oecophyla on the cocoa trees, the lower the population of the mirids”. The results was in consonance with the findings of Anikwe et al. (2010) that Cocoa trees infested by ants have very few other insects on such tree and also fewer mirid damage lesions on pods. Taylor, (1998) also reported that the African weaver ant effectively controls certain species of Homoptera (mealybug). Leston (1973) suggested that the ant mosaic in cocoa could be manipulated so as to reduce the incidence of major pests and disease vectors. 5.5 Influence of climatic factors (rainfall, temperature and relative humidity) on the population of S. singularis The presence of the insect pests in the farms depends on both the interactions of the climatic factors and the host plant factors which include: production and availability of cocoa pods for feeding and breeding as well as suitable temperature and relative humidity which are required for the survival of the pest (Idowu, 1989). 71 University of Ghana http://ugspace.ug.edu.gh The low number of Sahlbergella population during the rainy season was in consonance with Mariau (1999) who reported that very high rainfall could cause a temporary fall in the nymphal populations. Relative humidity was very high in July and August and this favoured the multiplication of Sahlbergella leading to the all time high populations in September in both the organic and the farmers farms where monitoring was not as effective as the institution farms. Sahlbergela population reduced gradually and consistency from November to March where it started rising again. This result agreed with earlier reports that mirid populations decline in periods of low humidity. When a water deficit appeared in the tissues of the cocoa tree, the mortality of the young stages was greatly affected leading to the belief that water was probably an extremely critical factor during periods of low humidity (Enwistle, 1972). From the result low numbers of Sahlbergella were recorded in the months of low mean Temperature eg, August. This confirms the report by Mariau that gradation in population begins to increase rapidly after the temperature cools down in the month of August (Mariau, 1999). The trend of Sahlbergella population was consistent in all the three systems and therefore has a positive correlation to the monthly mean values of Relative Humidity but the effects of Temperature and Rainfall were inconsistent and therefore have no significant effect. 72 University of Ghana http://ugspace.ug.edu.gh CHAPTER SIX 6.1 Conclusion The phenomenon of fluctuation in population of insects in nature has been attracting the attention of a number of workers including Biologist and mathematicians who have rendered valuable services by contributing mathematical precision to control insect population problems. Owusu Manu (1971) after studying the population of mirids was able to formulate mirid control strategy from the result he obtained. For a correct and scientific solution of pest problems, it is of importance to develop sound techniques for the estimation of population as well as for quantitative measurement of factors governing population fluctuations. The present study revealed that mirids were available throughout the year especially in the Farmer‟s farm and Organic farms. The populations of mirids were also very high on farms less than 30 years. Experimental managed farms recorded a high population of mirids in March but the Organic and the Farmer‟s farms had the peak populations in September. The lowest numbers of the insect pests recorded in the Experimental managed farms as compared to the other two systems was as a result of strict compliance of good Agricultural practices such as regular weed control, proper shade management, timely and effective pruning, monitoring insect pests and application of recommended pesticides 73 University of Ghana http://ugspace.ug.edu.gh From the results obtained, there were serious damages caused by other insect pests apart from the mirids which are of economic importance. Other insect pests identified included; Bathycoelia, Characoma, Anomis, Earias, mealybugs, termites, Aphids and Psyllids. Damages by Bathycoelia was very high especially in the Farmer‟s farms and from observation their percentage damages was similar to that of mirids meanwhile they were considered as minor pests of cocoa in 2009 (Awudzi et al., 2009). Natural enemies found in the survey include; Oecophyla, Camponotus, Crematogaster, Phiedole and spiders. Mirids populations were low in the cocoa farms with high populations of the ant species. Temperature and Rainfall have no significant effect on the populations of mirids. The result of this work, therefore, shows that a lot of factors which ranged from climatic factors to pod availability as well as the presence of natural enemies, especially ants, all come into play in determining the population dynamics of insects on cocoa. This knowledge provides a good basis for the development of an ecologically-based method of pest management. 6.1 Recommendations 1. Damage caused by Bathycoelia thalassina was similar to mirids especially in the Farmer‟s farms. 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