EVALUATION OF Jatropha curcas L. (EUPHORBIACEAE) AS A BIOPESTICIDE IN THE CONTROL OF INSECT PESTS COMPLEX OF AUBERGINE (Solatium melongena L.) BY VINCENT YAO EZIAH B.Sc. (Hons.) AGRICULTURE (CROP SCIENCE) A THESIS PRESENTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR INSECT SCIENCE PROGRAMME* UNIVERSITY OF GHANA LEGON. SEPTEMBER 1999 * JOINT INTERFACULTY INTERNATIONAL PROGRAMME FOR THE TRAINING OF ENTOMOLOGISTS IN WEST AFRICA. COLLABORATING DEPARTMENTS: ZOOLOGY (FACULTY OF SCIENCE) & CROP SCIENCE (FACULTY OF AGRICULTURE) THE DEGREE OF MASTER OF PHILOSOPHY (ENTOMOL< UNIVERSITY OF GHANA. University of Ghana http://ugspace.ug.edu.gh ^362275 S g > University of Ghana http://ugspace.ug.edu.gh Declaration I hereby declare that except for references to other people’s work, which have been duly cited, this work is as a result o f my own original findings and has neither been presented in whole nor in part elsewhere for any degree. Vincent Yao Eziah (Student) h (o a r Dr. D. Obeng-Ofori (Supervisor) University of Ghana http://ugspace.ug.edu.gh Abstract The potentials of aqueous seed extract and seed oil of the coral plant, Jatropha curcas L. (Euphorbiaceae) were evaluated as a biopesticide compared with aqueous seed extract of neem (Azadirachta. indica A. Juss) and cymethoate, (a commercially used synthetic insecticide) in the control of insect pests complex of aubergine (black beauty), Solanum melongena L. (Solanaceae) both in the laboratoiy and in the field. Three major insect pests of aubergine namely, Urentius hystericellus Richter (Homoptera: Tingidae) Aphis gossypii Glover (Homoptera, Aphididae) and Selepa docilis Butler (Lepidoptera; Noctuidae) collected from an aubergine field at the University of Ghana Farm, Legon that had not received chemical treatment for eight months were used to determine the levels of jatropha seed oil and aqueous seed extract that could induce 50 % mortality. Choice assays as well as the ovicidal effects of neem and jatropha products on S. docilis were investigated In the laboratory fifty percent mortality was induced in S. docilis, A. gossypii and U. hystericellus when they were exposed to aubergine leaves dipped for 3 sec in 1.5, 2.2 and 3.6 ml/1 seed oil of jatropha, respectively. Also 28.4 and 22.3 g/1 aqueous seed extract of jatropha induced 50 % mortality in A. gossypii and S. docilis, respectively. Higher concentrations of the extract (40-100 g/1) and oil (2-8 ml/1) on treated leaves inhibited feeding by the larvae of S. docilis, which died within 48 hrs. Ninety percent of U. hystericellus and 60 % of the larvae of S. docilis avoided leaf discs or filter paper treated with the seed oil or the aqueous seed extract of jatropha. Jatropha seed oil reduced hatchability by 21 % while aqueous seed extracts of neem and jatropha had no ovicidal effect on S. docilis. In the field, aqueous extract of jatropha (40 g/1), jatropha seed oil (4 ml/1), neem (75 g/1) cymethoate (2 m/1) were sprayed on weekly basis four weeks after transplanting. Results obtained showed that control (non-treated) differed significantly (P < 0.05) from other treatments in number of holes in fruits, marketable fiuit weight, number of fruits and number of thrips per plant. In addition, percentage fruits bored, marketable fruit weight per plant, percent leaf area defoliated by leaf feeders and yield in tonnes/ha differed University of Ghana http://ugspace.ug.edu.gh significantly (P< 0.01) from the control. Plant height at flowering and number of flower buds bored showed no significant differences (P = 0.05). Jatropha seed oil treatment gave slightly higher yield indices even though not significantly different (P= 0.05) from the other plant products and cymethoate. A significant (P < 0.01) positive correlation was observed between number of marketable fruits and fruit yield expressed in tonnes/h. Based on this findings jatropha seed extracts are good candidate biopesticide in controlling insect pests of aubergine and should be integrated into an overall management of agricultural pests. University of Ghana http://ugspace.ug.edu.gh Dedication ‘...Whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report: If there be any virtue and if there be any praise think on these things.’(Philippians 4, 8). Dedicated to my beloved wife, Martha Kwarshie; my son, Vincent Eziah Jnr and my mother, Florencia Ama Anyangeh. University of Ghana http://ugspace.ug.edu.gh Acknowledgement. I wish to give thanks and praises to the Lord, God Almighty for giving me the wisdom, vision and direction during the execution of this project. I am greatly indebted to Drs. D. Obeng-Ofori and E. O Owusu my hard working supervisors for their love, time, guidance and critical but constructive criticisms during the preparation o f this work. Professor J. N Ayertey (Head, Crop Science Department) deserves special mention for his encouragement and pieces of advice that has greatly contributed in bringing me this I am also grateful to my sponsors, DAAD In-Country fellowship who funded this programme. Many thanks also go to the staff of the Department of Crop Science particularly Bernard Boateng, Elvis Owusu-Appiah and William Asiedu Asante for their assistance in the j | laboratory and in the field. X Thanks are also due to Dr R. K. Akuamuah and Mr. S. A Asunka of Department of Chemistry for assisting me in the extraction of the seed oil of jatropha. It is also important to register my profound gratitude to Messrs Emmanuel Techie and Henry Noamesi who helped me in the collection of the seeds of the plants used in the experiment. I am also grateful to my wife Martha Kwarshie, my son, Vincent Eziah Jnr. my brothers and sisters, my mother and other well wishers and sympathizers for their prayers and moral support. Finally, 1 wish to thank my course mates: Solomon Darko, Clement Akotsen, Stella Tamunjoh, Henry Sintim and Anim Sakyi for their cooperation, love and care during our coursework. May the Almighty God bless and keep all of you including those 1 have not been able to mention here. May he let his face to shine upon you and be gracious unto you. May he lift his countenance upon you and give you peace. Amen. v University of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENTS. Title Page Declaration ... ... i Abstract ... ... ii Dedication ... ... iv Acknowledgment v Table of contents ... ... vi List of tables ... ... x List of figures ... ... xi List of abbreviations ... xii List of plates ... ... xiii List of appendices xv 1.0 General introduction ... ... 1 2.0 Literature review. ... ... 4 2.1 Origin and botany of aubergine ... 4 2.2. Agroecological suitability ... 5 2.3 Nutritive value and uses ... 5 2.4 Yield ... 5 2.5 Insect pests ... 6 2.6 Control of insect pests of aubergine ... 10 2.1 Neem ... ... 12 2.7.1 Botany ... ... 12 2.7.2 Ecology ... ... 13 2.7.3 Active ingredients.. 14 2.7.4Neem as a pesticide ... ... 15 2.8 Phvsic nut (Jatropha curcas L.') . . . . . 19 2.8.1 Botany and ecology ... ... 19 2.8.2 Medicinal and pesticidal properties ... 20 vi University of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENTS. Title Page Declaration ... ■ • 1 Abstract ... • ■ ■ ii Dedication ... • ■ lv Acknowledgment v Table of contents ... ... vi List of tables ... ... x List of figures ... ... xi List of abbreviations ... xii List of plates ... ... xiii List of appendices xv 1.0 General introduction ... ... 1 2.0 Literature review. ... ... 4 2.1 Origin and botany of aubergine ... 4 2.2.Agroecological suitability ... 5 2.3 Nutritive value and uses ... 5 2.4 Yield ... 5 2.5 Insect pests ... 6 2.6 Control of insect pests of aubergine ... 10 2.7 Neem ... ... 12 2.7.1 Botany ... ... 12 2.7.2 Ecology ... ... 13 2.7.3 Active ingredients.. 14 2.7.4 Neem as a pesticide ... ... 15 2.8 Physic nut (JatrophacurcasL.) ... 19 2.8.1 Botany and ecology ... ... 19 2.8.2Medicinal and pesticidal properties ... 20 vi University of Ghana http://ugspace.ug.edu.gh 3.0 Materials and methods ... 22 3.1 Laboratory studies ... 22 3.1.1. Extraction of jatropha seed oil ... 22 3.1.2 Preparation of aqueous seed extract of jatropha 23 3.1.3 Toxicity of jatropha aqueous seed extracts and oil to Aphis gossypii 23 3.1.4. Toxicity of jatropha aqueous seed extract and oil to the larvae of Selepa docilis 24 3.1.5 Effect o f jatropha seed oil on the brinjal lace bug, Urentius hystericellus 25 3.1.6 Choice bioassay 25 3.1.7 Ovicidal effects of jatropha seed and neem products on S. docilis 26 3.1.8 Effect ofjatropha extract on the behavior of Aphids gossypii 27 3.2 Field studies 27 3.2.1 Experimental site ... ... 27 3.2.2 Data Collection ... ... 28 3.2.3 Data analysis ... ... 29 4.0 Results ... ... 30 4.1 .Laboratory bioassavs ... 30 4.1.1 T oxicity of jatropha aqueous seed extract and oil to Aphis gossypii. 3 0 4.1.2 Toxicity of jatropha aqueous seed extract and oil to the larvae of S. docilis 30 4.1.3. Effect of jatropha seed oil on the lace bug, Urentius hystericellus 35 4.1.4 Choice bioassays 36 4.1.5 Effect of jatropha and neem products on S. docilis eggs. 38 4.1.6 Effect of jatropha extracts on the behavior of Aphis gossypii 38 4.2. Field work 39 5.0 Discussion 56 5.1 Laboratory bioassays ... 56 5.2 Field work ... ... 60 5.2.1 Insect pests encountered in the nursery. 60 University of Ghana http://ugspace.ug.edu.gh 5.2.2 Insect pests encountered in the field. 60 5.2.3 Beneficial arthropods 68 5.2.4 Effect of the various treatments and pests on growth and yield indices.68 6.0 Summary and Conclusion 71 References ... ... 74 Appendices ... ... 87 University of Ghana http://ugspace.ug.edu.gh Table Page 1 Major insect pests of aubergine worldwide 9 2 Feeding effect of jatropha seed oil on the larvae of S. docilis 35 3 Effect of neem and jatropha products on S. docilis 38 4 A list of insects encountered on eggplant {Solanum melongena L.) during the sampling period. 40 5 Relative abundance of insects collected from S. melongena under the various treatments at the University farm, Legon. 41 6 Effect of the treatments on damage caused to the fruit of S. melongena 53 7 Effect of the treatments on chlorotic leaf damage, % leaf defoliation and plant height at flowering by the pests. 54 8 Effect o f the treatments on the yield of S. melongena 54 9 Mean number of thrips per treatment. 55 10 Number of thrips recorded for NS at different times of the day. 55 List of tables University of Ghana http://ugspace.ug.edu.gh List of figures Figure Page 1. Responses of S. docilis and A. gossypii to varying levels of jatropha (aq) seed extracts 31 2. Responses o f S. docilis and A. gossypii to varying levels of jatropha seed oil. 32 3. Response of U. hystericellus to varying levels o f jatropha seed oil 33 4. Population trend of E. lybica on treated eggplants. 48 5. Population trend of S. docilis on treated eggplants 49 6. Population trend of U. hystericellus on treated eggplants. 50 7. Correlation between yield in tonnes per hectare and number of fruits per plant. 51 x University of Ghana http://ugspace.ug.edu.gh List of abbreviations. 1. ai Active ingredient. 2. ha Hectare 3. mg Milligramme 4. g Grammes 5. Cal Calorie 6. Kg Kilogramme 7. Wt Weight 8. g/1 Grammes per litre 9. cm Centimeter 10. t/ha Tonnes per hectare 11. h Hours 12. aq Aqueous 13. ml Milliliter 14. m Metre 15. LSD Least Significant Difference 16. ANOVA Analysis of variance 17. GMT Greenwich Mean Time 18. JSKE Jatropha seed kernel extract 19. JSO Jatropha seed oil 20. NSKE Neem seed kernel extract 21. CY Cymethoate 22. NS No spray 23. EC Emulsifiable Concentrate xi University of Ghana http://ugspace.ug.edu.gh List of plates Plate Page 1. Feeding pattern of the larvae of S. docilis on aubergine leaves treated with seed extracts of jatropha 34 2. Preference for treated and untreated portions of filter paper by U. hystericellus 36 3. Preference for treated and untreated leaves A, (aq); B, (seed oil of jatropha) of S. docilis. larvae 37 4 Comparison of the feeding pattern by the larvae of S. docilis on treated and untreated aubergine leaves. 37 5. Orientation o f A. gossypii to treated and untreated leaf discs. 39 6. Damage to plant caused by the larvae of S. docilis 42 7. S. docilis 42 8. Damage by the larvae of E. admota 43 9. Adult E. admota 43 10. Chlorotic leaf surface caused by Tetrcmychus sp. Infestation 44 11 Leaf infestation by U. hystericellus. 44 12 The fruit and shoot borer, L. orbonalis 45 13. Larvae of the fruit and shoot borer, L. orbonalis 45 14. Tunnels created in the fruits by emerging larvae of L. orbonalis 46 15. Internal damage to fruit by the larvae of L. orbonalis 46 16.Unidentified parasitoid associated with larvae of S. docilis showing the pupal case. 47 xii University of Ghana http://ugspace.ug.edu.gh Appendices. Appendix Page 1. ANOVA, No. ofholes in fruits 87 2. ANOVA, % Bored fruits 87 3. ANOVA No. of flower buds bored 87 4. ANOVA Effect of the treatments on the chlorotic leaf damage by the pests. 88 5. ANOVA % leaf area defoliated by leaf feeders. 88 6. ANOVA, Plant height at flowering. 88 7. ANOVA Marketable fruit weight per plant. 89 8. ANOVA Marketable fruit weight (g) 89 9. ANOVA Number of fruits per plant. 89 10. ANOVA, Yield in tonnes per hectare. 90 11. ANOVA, Number of thrips per plant. 90 12. Effect o f jatropha aqueous seed extract and oil on A. gossypii, S. docilis and U. hystericellus. 91 University of Ghana http://ugspace.ug.edu.gh 1.0 GENERAL INTRODIJTION Aubergine (Solarium melongena L.) originated from East Indies where it is called brinjal and was introduced into Europe and other parts of the world including Africa (Norman, 1992). Several varieties exist and differ considerably in size, shape, colour and maturity period. The crop is very important for its nutritive values and even though it is primarily grown for local consumption, it is exported in Niger, Senegal, Cote d’Ivoire and Ghana to European countries (Norman, 1992). It is widely grown in Ghana especially in the Greater Accra region where it has a great potential to increase income levels and standard of living. Factors such as availability of good seed, soil fertility, diseases and pest are constraints to the cultivation of the crop. Among these, insect pest problems are the most important. The major pests include leaf feeding caterpillars and beetles, stem and fruit borers, leafhoppers as well as mealybugs. Borah (1995) also listed Aphis gossypii and Epilachna sp as major pests of the crop in India. Damage by the fruit and shoot borer for instance, has been reported to range between 27 and 61 % in India (Grewal et al., 1995). In States such as Punjab and Haryana, losses up to 63 % have been reported (Dhankhar et al., 1977). The borer is not only limited to India but also Malaysia, South Africa and Congo (Dhankhar, 1988). In central Accra, Ghana, for example, as high as 100% yield loss on farmers’ farms due to insect pest infestation is not uncommon (V. Y. Eziah Personal observation). 1 University of Ghana http://ugspace.ug.edu.gh Control of these pests is mainly by the use of synthetic insecticides. Most farmers use very high doses and mixtures of synthetic insecticides indiscriminately to control pests of aubergine. Synthetic pesticides while valued for their effectiveness and convenience, can pose problems when misused. Some of these are environmental pollution, development of resistant strains of insects, health hazards and toxicity to non-targeted organisms. In developing countries, additional problems include prohibitive cost, supply uncertainties and misuse. In Ghana, gross misuse of insecticides has led to the development of resistant strains of insect pests of some vegetables, and a call for national monitoring network to monitor insecticide use, and resistance development in all major insect pests (Owusu in press). There is, therefore, the need to search for cost effective, agronomically sustainable and environmentally friendly methods of controlling pests of aubergines. Several plant species have been shown to have insecticidal properties (Irvine, 1961; Zanno, 1974; Schmutterer 1990). One such plant is the neem tree; Azadirachta indica A. Juss (Miliaceae), whose crude extract and oil have been used successfully in pest management programmes (Schmutterer, 1990). Additionally it possesses medicinal properties and it is available locally. It therefore provides a safe and relatively cheap source of control agent that is biodegradable and available to the resource poor farmers. 2 University of Ghana http://ugspace.ug.edu.gh The seed extract of the coral plant Jatropha gossypifolia L. has been shown to have .insecticidal properties and several medicinal properties (Irvine, 1961). The most common species of the genus Jatropha in Ghana is curcas L. It is normally used for fencing and can easily be propagated by seeds and stem cuttings. Cobbinah and Appiah- Kwarteng. (1989) showed that the oil of Jatropha curcas confers effective protection on maize and cowpea against Callosobruchus maculatus F. and Sitophilus zeamais Motsch.. They also reported that the oil of jatropha emulsion significantly reduced the feeding activity of Zonocerus variegates L. The oil has also been shown to be effective against cotton stem borers in The Philippines (Solsoloy, 1995). The phorbol extracts have also been shown to have insecticidal properties (Irvine, 1961) but little research has been done on these products to evaluate their potential for the control of field pests. It is therefore important to carry out further studies on the plant and evaluate its protectant potential for the control of insect pest complex of aubergine This work was carried out with the following objectives. a. To determine the insect fauna associated with aubergine. b. To evaluate the efficacy of Jatropha curcas seed oil and aqueous seed extract against eggplant insect pests complex. c. To investigate the effect of jatropha products on indigenous natural enemies. d. To establish 50 % lethal dose (LD50) of J. curcas for the major insect pests of aubergine if proved to be effective. University of Ghana http://ugspace.ug.edu.gh 2.0 LITERATURE REVIEW 2.1 Origin and botany. Eggplant, Solatium melongena L. belongs to the family Solanaceae. It is exotic to West Africa and thought to have first been cultivated in India and China where it is known as brinjal (Norman, 1992). From there, it was spread to Europe by Maorish invaders of Spain. They are perennial crops grown as annuals. Several cultivars such as Black beauty, Florida high bush, Black magic purple, Long green, Long purple are grown both in the wet and dry seasons (Town, 1964). These cultilvars also vary considerably in size, shape, and colour. The stem and leaves are covered with umbrella shaped hairs. The flowers, with white, mauve, or purple corolla have yellow stamens, opening via a pore at the tip. Flowers are solitary but occasionally in twos. Fruits are entire with no cavity in which seeds are embedded. The calyx covering the upper part of the fruit can be smooth or spiny, green or purplish. The seeds are glabrous and in the sixth month after extraction, germination can be erratic. This can be enhanced by placing the seeds in the refrigerator at 4-6 °C for about 21 days. 4 University of Ghana http://ugspace.ug.edu.gh 2.2 Agroecological suitability. The eggplant is a warm season crop; it prefers relatively high temperature for growth and development. The optimum day and night temperatures range from 25-35 °C and 20-27 °C, respectively. It does well in soils rich in organic matter and a pH range of 5.5-6.8 is desirable for successful production (Messiaeh, 1992). 2.3 Nutritive value and use. The fruits contain 93.5 % moisture. The nutrient value per 100 g of fresh edible portion are energy, 20 cal; carbohydrate, 4 g; protein, 1.1 g; fat, 0.1 mg; fibre, lg; calcium, 7 mg; phosphorus, 25 mg; iron, 0.4 mg; vitamin A, 70 I.U; thiamin, 0.09 mg; ascorbic acid, 15 mg; riboflavin, 0.2 mg nicotinamide, 0.6 mg and niacin, 0.6 mg (Norman, 1992). The fruits are cut into pieces and used in stews or boiled and ground for the preparation of soups. It is also sometimes fried or stuffed with minced meat and either fried or baked. 2.4 Yield. Aubergine produces between five to ten fruits per plant and the more the fruits the smaller the size. An individual fruit may weigh between 0.1 - 1.5 kg depending on the cultivar. Akinlosotu (1979) reported yields up to 35.7 t/ha while Nsowah (1969) showed that fruit yield diminished with age of plant. In fact, 70% of total yield are produced during the first eight to nine weeks after transplanting. He also showed that fruit yield was higher in the main wet season than in the minor wet season in the forest zone of Ghana and that yields increase with early planting. Kogbe (1983) also reported that yield varies with spacing and recommended 90 x 60 cm, giving yields of up to 54.8 t/ha. 5 University of Ghana http://ugspace.ug.edu.gh 2.5 Insect pests. A number of insect pests from six orders, namely, Coleoptera, Heteroptera, Homoptera, Isoptera, Lepidoptera, and Orthoptera attack egg plant (Chritchley, 1997) and may feed on young seedlings, leaves, flowers, flower buds and the fruit (Table 1). Messiaeh (1992) reported that probably the most serious insect pest that attacks the crop is Thrips palmi Kamy (Thysanoptera; Thripidae). In French West Indies, it has ruined the production of eggplant for export. He also stated that T. palmi causes less damage in wetter areas where rainfall exceeds 2500 mm per annum. Tommasini et al., (1997) reported that other thrips especially Frankliniella occidentalis Pergande (Thysanoptera; Thripidae) (the most harmful one) and Thrips tabaci Lind. (Thysanoptera; Thripidae) also attack the crop. In a survey conducted in Homestead Florida by Castineiras et, al., (1977) to determine the relative abundance of thrips on leaves, flowers and fruits, they showed that T. palmi was more abundant on leaves (x = 17. 97 ± 5.07) than on fruits (x = 3.22 ± 0.7) and flowers (x = 0.9 + 0.3). They further stated that the population was low on the youngest leaf (x = 1.75 ± 0.28) and high on the oldest leaf (x =50.83 + 11.64) and therefore recommended the fourth leaf from the terminal bud of a branch for population sampling studies. Of the twelve vegetable crops surveyed for infestation by T. palmi in Thailand, Malaysia and The Philippines, aubergine appeared to be the most frequently infested crop by thrips (Kajita et al., 1996). Kapoor et al., (1997) reported that Tetranychus cinnabarinus Boisd. and phytoseiids are the main pests of aubergine in India; while Mishra and Mishra (1996) stated that 6 University of Ghana http://ugspace.ug.edu.gh Leucinoides orbonalis Guen (the shoot and fruit borer) can cause damage of between 30 and 50 % to the fruit. In a study conducted by Grewal et, a l, (1995) to screen 12 cultivars of aubergine to the fruit borer, infestation levels ranged from 27 to 61 %. Dhankar (1988) reported that the shoot and fruit borer is the major constraint to the production of eggplant not only in India subcontinent but also in South Africa, Congo, and Malaysia. In India, Hampson (1896) first reported the occurrence of the fruit and shoot borer on eggplant. It remains active in India throughout the year because of successive cropping of eggplant, particularly in areas having moderate climate. The pest attacks eggplant from nursery to maturity. The caterpillars of the fruit and shoot borer bore into young shoots causing drooping and withering of growing tips. Later they bore into flower buds and fruits. The buds are shed whereas the fruits bear circular holes rendering them blemish and unmarketable. Yield losses vary with season and location, being maximum during the period of high temperature and relative humidity. In India, the States in which very high losses have been reported are: Haryana 63 % (Dhankhar et al., 1977), Punjab 61 % (Singh and Guram, 1967), Tamil Nadu 54 % (Srinivasan and Gowder, 1959), Bengal 50 % (Som Chaudhary, 1973), Orissa 43 % (Panda et al., 1971). Vitamin C in affected fruits is reported to be reduced by 60 % (Hami, 1955). The brinjal lace bug, Urentius hystericellus Richter, is another insect that attacks the leaves from the under surface, secreting toxic saliva that turns the leaves chlorotic and 7 University of Ghana http://ugspace.ug.edu.gh distort. Affected plants become stunted (Fimpong and Buahin, 1997). The moth, Selepa docilis Butler (the eggplant skeletonizer), causes severe defoliation of the leaves and can result in stunted and withered plants (Frimpong, 1981). Eublema admota Fldr. the leaf worm, also attacks the terminal buds of the plant boring through the apex and feeds inside rolled up leaves (Norman, 1974). They generally appear soon after transplanting, mainly in the dry season. The larvae of Scrobipalpa blapsigona Meyrick also bore into the buds, which later become spherical instead of cylindrical and are invariably shed. Heavy attack can result in heavy losses in yield. Sapsuckers Such as Anoplocnemis curvipes Fab. (Heteroptera: Coreidae), Helopeltis bergrothi Reuter (Heteroptera: Miridae), Empoasca lybica de Berg. (Homptera: Cicadellidae) attack young fruits and shoots causing them to become distorted. Aphis gossypii Glover (Homoptera: Aphididae) and Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) feed by sucking sap from the under surface of the leaves, secreting honeydew on the upper surface that encourage growth of sooty mould. They also act as vectors of various viral diseases including leaf curl and mosaic. Coleopterans such as Diabrotica sp, (Coleoptera: Chrysomelidae) Epitrix aethiopica Wse. (Coleoptera: Chrysomelidae), Ootheca mutabilis Sahl. (Coleoptera: Chrysomelidae) and Epilachna elaterii Rossi (Coleoptera: Coccinelidae) cause considerable amount of damage to the leaves and sometimes fruits. 8 University of Ghana http://ugspace.ug.edu.gh Table l.Major insect pests of aubergine worlwide. Scientific name Plant part attacked Leucinodes orbonalis Guen.(Lepidoptera: Noctuidae) Shoot and fruit Tetranychus urticea Koch.(Acarina: Tetranychidae) Leaves and stems Amrasca devastans Devastant (Homoptera: Ciccadellidae ) Leaves Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) Leaves Diabrotica sp (Coleoptera: Chrysomelidae) Leaves Epitrix aethiopica Wse. (Coleoptera: Chrysomelidae) Leaves Ootheca mutabilis Sahl (Coleoptera: Chrysomelidae) Leaves Epilachna elaterii Rossi (Coleoptera; Coccinelidae) Leaves Anoplocnemis curvipes Fab. (Heteroptera; Coreidae) Young Shoots Helopeltis bergrothi Reuter (Heteroptera; Miridae) Shoot Empoasca tybica de Berg. (Homopera; Cicadellidae) Leaves Eublema admota Fldr. (Lepidoptera; Noctuidae) Terminal buds Selepa docilis Butler (Lepidoptera; Noctuidae) Leaves Urentius hystericellus Richter (Heteroptera; Tingidae) Leaves Franklimella occidentalis Pergande (Thysanoptera; Thripidae) Leaves, fruit and flower Thrips palmi Karay (Thysanoptera; Thripidae) Leaves, fruit and flower Aphis gossypii Glover (Homoptera, Aphididae) Leaves and stem Source: Chrichlev (1997) University of Ghana http://ugspace.ug.edu.gh A number of insect pests attack aubergines in the field and, therefore, different control measures have been adopted at different places against these pests. In an integrated pest management programme in a greenhouse, the pirate bug, Orius laevigatus Fieber was able to control effectively the exotic thrips species Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) despite chemical insecticides sprayed against Aphis gossypii. The pirate bug releases, conducted as soon as thrips were detected, allowed an early interaction to be established between the prey and the predator at low level of density (Tommasini et al., 1997). In a glasshouse experiment at Howard David Farm, Jersey, British Isles, Bennison et al.,(1996) showed that Trialeurodes vaporariorum Westw. (Homoptera: Aloyrodidae) and Thrips tabaci were well controlled by Encarsia formosa Gahan (parasitoid) and Amblyseius accumeris Oudm., respectively. Also the use of Therodiplosis sp and Phidoletes sp as bioagents with one a spot treatment using fenbutin oxide effectively controlled Tetranychus urticea Koch Aphis sp were controlled by a combination of the parasite Aphelinus abdominalis Dalm., (Hymenoptera: Aphilinidae), Aphidius colemani Viereck and Aphedoletes aphidimyza Rond, (parasites) with only one spot treatment of nicotine to reduce damage by Aulacorthum solani Kalt (Homoptera : Aphididae). 2.6 Control of insect pests of aubergine. 10 University of Ghana http://ugspace.ug.edu.gh Chemical control of thrips has also been investigated and out of 11 insecticides tested, high level of tolerance was observed (Cermeli et al., 1993). It was, however found that Flufenoxuron, Imidacloprid Chlorfluazuron and Oxamyl were most promising insecticides, in order of effectiveness, when applied at five days interval. However, no insecticide was more than 80.5 % effective. Etienne et al., (1990) showed that rainfall depresses the population of the pest and that increased use of insecticides increases the pest population. This is because the activities of predator are reduced in treated areas. Kawai and Kitamura (1990) also stated that physical prevention of invasion, reduction of population density on seedlings and mass trapping using sticky traps were effective methods of controlling Thrips palmi attacking the eggplant in greenhouses. Nagai et al., (1988) demonstrated that Flufenoxuron inhibited the ecdysis of first instar nymphs and metamorphosis of second instar nymphs to pupae of Thrips palmi but did not affect the rate of development and fecundity of females. It has also been shown that carbaryl, quinalphos, endosulphan, cypermethrin, deltamethrin and fenvalerate are effective against the larvae and adults of Epilachna vigintioctopunctata Fab. while dimethoate and fenpropathrin were effective against the adult only (Nagai et al., 1992). Bacillus thuringiensis subspecies tenebrionis have been shown to markedly affect percentage egg hatchability and dispersal of larvae of the Colorado potato weevil, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) (Ghidiu et al., 1994). An application of 7.02 1/ha in the field, for example, produced only 5 % dispersal of the 11 University of Ghana http://ugspace.ug.edu.gh larvae from the treated eggs. It has also been shown that the hymenopteran, Edovum putteri Grissell produced 67 % egg parasitism of the potato beetle (Schroder and Athanas, 1995). The shoot and fruit borer, Leucinodes orbonalis has also been effectively controlled by the use of Carbofuran 3G at 30 kg/ha applied every 20 days after transplanting or Cypermethrin 10 EC at 1 ml/1 water applied at first signs of infestation, followed by three subsequent sprayings at 30 day interval (Chowdhury et al., 1993). The insect is also susceptible to Endosulfan (Verma et al., 1993). Extracts from seeds of Thevetia nerifolia L. roots of Nerium oleander L.and leaves of Lantana camara L. and Ocimum sanctum Wiild.at 1.0 % treatment of aubergine leaves caused 90 % mortality to the larvae of Epilachna vigintioctopunctata exposed to the treated leaves (Satpathi and Ghatak 1990). Petroleum extracts from the leaves of Bougainvillea spectabilis Willd. produced 100 % mortality in Henosepilachna vigintioctopunctata when exposed to aubergine leaves treated with 0.2 % and 0.5 % of the extracts. The same mortality was recorded for extracts of Azadirachta indica applied at 0.5% (Rao el al., 1992). 2.7 Neem (Azadirachta indica A. Juss) 2.7.1 Botany Neem, Azadirachta indica A. Juss (Miliaceae) is native to India and Burma which contains an estimated 18 million tress with most of them lining along the roadsides. It is 12 University of Ghana http://ugspace.ug.edu.gh a fast growing plant that usually reaches a height of 15-20 m and under favourable conditions; it can grow as high as 35-40 m tall. It is seldom leafless but under extreme circumstances such as an extended dry period, it may shed most or nearly all its leaves. The branches spread widely. The fairly dense crown is roundish or oval and may reach a diameter of 15-20 m in old, freestanding trees, (Schmutterer, 1995). The trunk is relatively short, straight with a girth of 1.5-3.5 m. The bark is hard, fissured or scaly and whitish-grey to reddish-brown. The root system consists of a strong taproot and well- developed lateral roots. The unpaired pinnate leaves are 20-40 cm long and medium to dark green leaflets, which number up to 31, are approximately 3-8 cm long. Very young leaves are reddish to purplish in colour. The white fragrant flowers are arranged in axillary, more-less drooping panicles, which are up to 2 cm long. The inflorescences, which branch up to third degree, bear approximately 150 and occasionally up to 250 flowers (Gruber, 1991). The glabrous fruits are green when young and yellowish-green to yellow when matured. The exocarp of the fruit is thin and the mesocarp is yellowish white and very fibrous. The endocarp contains, in most cases only one seed surrounded by a brown testa (Schmutterer, 1995). 2.7.2 Ecology. The tree is famous for its drought resistance. It thrives well in areas with annual rainfall between 400-1200 mm though it can also grow well in areas with annual rainfall below 400 mm. Neem does well in different types of soil, but it seems to develop best on well- 13 University of Ghana http://ugspace.ug.edu.gh drained, deep sandy soils. A soil pH between 6.2 and 7.0 seems to be best for the tree. Neem, as a typical tropical plant does best with temperatures ranging from 21-32 °C although it can tolerate high to very high temperatures. Temperatures below 4 °C and frost are unfavourable and may result in the shedding of leaves or even death of young plants (Schmutterer, 1995). Exracts of neem fruits, seeds, seed kernels, twigs, stem bark, root bark have been shown to possess antifeedant, insecticidal, insect growth disrupting, nematicidal, fungicidal (Jacobson, 1989; Rand-Hawa and Parma, 1993; Schmutterer and Ascher 1984, Schummutterer, 1990) anti-inflammatory (Dhawan and Patnaik, 1993) and anti- tumor (Fujiwara et al., 1982; 1984) and other activities. More than one hundred compounds have been isolated from various part of the tree and several reviews on constituents of neem (Champagne et al., 1992; Koul et al., 1990; Taylor, 1984) have been published to date. 2.7.3 Active ingredient. Most of the active ingredients belong to the group of tetranorterpenoids, but biologically active diterpenoids, triterpenoids, pentaterpenoids and a smaller number of nonterpenoidal ingredients have also been isolated. The major biologically active fcomponent is azadirachtin whose highly complicated structure was first reported by Zanno (1974) and Nakanishi (1975). Neem compounds are systemic in some plants. Potato, for instance, does not take up azadirachtin whereas beans do (Schmutterer, 1990). 14 University of Ghana http://ugspace.ug.edu.gh Azadirachtin has attracted considerable interest during the past two decades because of its dual forms of activity: as an insect growth inhibitor at lower concentration, and an insect antifeedant at high concentrations if applied by feeding or topically (Champagne et al.,. 1992; Jacobson, 1989; Rembold, 1989). Since its correct structure was established (Kraus et al., 1985) a number of azadiractin derivatives and analogs with modified ester groups attached to carbon-1 and carbon-3 have been isolated from neem (Rembold eta l., 1987). The content of azadirachtin has been shown to vary greatly among different ecological zones and countries (Ermel et al., 1987). However, the factors that influence the quantity of the active ingredient concentration are not clearly understood. Nevertheless, edaphic, climatic, as well as pre and post harvest conditions could be contributory factors. 2.7.4 Neem as a pesticide. Both purified and crude extracts of neem seed kernel have been used widely against insect pests both in the field and in storage. Topical application of neem oil on the nymph of grassshopper and Schistocerca gregaria Forsk. (Othoptera: Acrididae) showed a gradual destruction of the antenna (Nicol and Schmutterer, 1991). Heyde et al., (1984) found in assays using three species of plant and leafhoppers on rice, that, settling by the brown plant hopper, Nilaparvata lugens Stal and the white back plant hopper, Sogetella furcifera Horv, (Homoptera: Cicadillidae) was progressively reduced by increasing concentrations of neem oil (1-50 %). Adults of the green leafhopper, Nephottetix virescence Dist. (Homoptera: Cicadellidae) were not or only slightly repelled even by application of 50% neem oil. 15 University of Ghana http://ugspace.ug.edu.gh Opposition is also reduced by the application of 4-5% neem seed kernel extract. Saxena and Basit (1982) showed that the egg laying of Amrasca devastans on cotton treated with neem oil was significantly reduced. Saxena et al., (1981) demonstrated; in the laboratory that the rice leafhopper Cnaphalocrocis medinalis Gn. (Homoptera: Pyralidae) laid only one third the number of eggs on neem oil treated rice plants as on control plants. A strong antiovipositional effect of neem oil on bruchids has also been recorded. Yadav (1985) showed that when green gram seeds were treated with neem oil (2-50 mg per 100 g) Callosobruchus maculatus never oviposited on seeds treated with 50 mg oil per 100 g while C. chinensis L. and C. analis L. did not oviposit from 40 mg oil per 100 g upwards. In Taiwan, for some unknown reason, Klemm and Schmutterer (1993) cited by Schmutterer (1995) showed that Plutella xylostella L. (Lepidoptera: Yponomeutidae) preferred neem treated cabbage to the untreated as very high number of eggs were laid on the treated as against the untreated. The brown planthopper, N. Lugens failed to produce the normal courtship signals after topical application of 2.5 or 5 (j.g neem oil per insect. This observation was also made when the insects were exposed to caged rice plant sprayed with 3 % neem oil (Saxena et al, 1993). Experiments in India have proved the repellent effect of aqueous neem seed extract (10 g/1) against Empoasca lybica, Aphis gossypii and Epilachna beetles on brinjal. Asari and Nair (1972) reported that neem performed better in post treatment counts showing 16 University of Ghana http://ugspace.ug.edu.gh immediate repellency. Damage by the flea beetle, Epitrix fuscula Croch and the corolado potato beetle Leptinotarsa decemlineata, was significantly reduced by weekly application of an ethanol extract of neem seeds, whereas the neem dust formulation was not effective in the field trial (Reed and Reed 1985). It has also been shown that application of 5, 10 and 20 % neem oil to eggplants at the pre­ flowering, fruiting and post fruiting stages effectively controlled S. docilis with the 10% formulation causing immediate mortality. The lace bug, Urentius sp and the grasshopper, Zonocerus variegatus were strongly repelled from treated plants. However, a concentration o f 10 % and 20 % in the pre flowering application resulted in phytotoxicity effects (Cobbinah and Osei-Owusu, 1988). When exposed to sunlight neem products degrade and lose their activity. Typically, the crude extract remains active for only eight days when exposed to the sun’s ultra violet rays. The fact that neem products are natural does not mean they are environmentally benign. In a trial, both tadpoles and mosquito eating fish, gumbusia died when neem extracts were applied to the water in which they were (Jotwani and Srivastava, 1981). Also certain neem compounds can damage plants in green house and in the field. Cabbage treated with neem produced medium sized heads, whereas in tomato growth and yield were reduced (Jacobson, 1989). In Ghana neem is traditionally used for the treatment of malaria (Abbiw, 1990). Research work done in different parts of Ghana showed that neem products are effective University of Ghana http://ugspace.ug.edu.gh against a wide range of both field and storage pests of vegetables, legumes, cereals and plantation crops. The target species include the diamondback moth, fruit flies, mealy bugs, aphids, pod borers flower borers, and bud borers (Foijoe, 1995; Kottoh, 1997; Adzaho, 1997; Afreh-Nuamah et al., 1998). ). It has also been shown that an application of 50-75 g/1 provided a good protection for garden egg pests and increasing dry matter content significantly (Owusu-Ansah et al., 1998). Aqueous extracts of neem seeds and leaf extracts has been reported to reduce the incidence of Megalurothrips sp infesting cowpeas and increase yields significantly in Northern Ghana (Tanzubil, 1991). Cobbinah and Osei-Owusu (1988) have demonstrated that various concentrations of neem emulsion reduced the incidence of the noctuid Selepa docilis, the tangid Urentius sp. and the acridid, Zonocerus variegatus on aubergine. Neem products have also played a significant role in grain storage. It has been shown to provide an effective protection against grain weevils, grain beetles, grain borers, cowpea beetles and several species of storage moths (Cobbina and Appiah-Kwarteng, 1989; Owusu Akyaw, 1991; Baba Niber, 1994; Allotey and Dankwah, 1994; Obeng-Ofori, 1997). Maize kernels treated with neem oil or ash were reported to have been damaged less by Sitophilus zeamais than untreated kernels while derivatives of neem inhibited oviposition and/or deterred feeding (Cobbinah and Appiah-Kwarteng, 1989). Tanzubil et al., (1987) showed that neem fruit dust at 10% by weight of seed protected stored cowpea for at least 4 months against Callosobruchus maculatus while the leaf dust (10%) seed weight were effective for 3 months. Foijoe, (1995) and Kottoh, (1997) also showed that 18 University of Ghana http://ugspace.ug.edu.gh some natural products such as garlic, (Allium sativum L.) and hot pepper (Capsicum frutenscens L.) provided a synergistic effect on neem products. 2.8 Physic nut (Jatropha curcas L.) 2.8.1 Botany and ecology. The coral plant Jatropha curcas (Euphorbiaceae) is a tropical crop and native to America and Central America but is widely cultivated in many Latin American, Asian and African countries as a hedge (Irvine, 1961). It has become o f interest to various development agencies because it adapts well to semi-arid and marginal areas (Heller, 1996). The plant is a shrub or tree up to about 6 m high. It is easily propagated by seed and stem cuttings and can be trimmed to any height. It is often planted over graves and sometimes to mark the limits of fields (Visser, 1975). The stem is thick, grey, glabrous and often twisted. It is almost leafless in the dry season. The leaves are about 8 cm in diameter and generally 3-5 digitately lobed to beyond the middle. It has glandular fruits containing three seeds, which are rich in oil (Heller, 1996). The plant has several English names such as physic nut, pignut, purging nut, Barbados nut etc. The plant is widely distributed in Ghana. In Ashanti it is called ‘Kaagya’, in Fante, ‘Aburokyiraba’ or ‘Akandedua’; in Ga, ‘Kpitikpitso’; in Ada, ‘Kitigbletso’ in Ewe, ‘Babatsi’, ‘Gbomagbotsi or 'Kporti.’ (Irvine, 1961). The plant is normally planted as a hedge to protect crops. It is usually used in the villages for fencing and the seeds are easily reached by hand (Irvine, 1961). 19 University of Ghana http://ugspace.ug.edu.gh 2.8.2 Medicinal and pesticidal properties. The plant has a lot of medicinal properties. The juice of the leaves is used in Ghana for the treatment of sores in babies’ tongues; the yellowish-brown substance in the pith of old stems is used for headaches, which induces the patient to sneeze (Irvine, 1961). It has been shown to be a very effective pesticide. Its leaves and fruits are poisonous to livestock. The plant is listed as a fish poison. The bark contains 37% tannin and the seed contains a taxalbumen whose chief poison is curcin, a phytotoxin, which remains in the cake rendering it unsuitable as cattle feed. (Watt and Breyer-Brandwijk, 1962). The oil content o f the seed ranges between 50-58 % and semi-drying and is formed from esters of palmitic and stearic acid (10-17%), Oleic acid (45-62%), linoleic acid (18-45%). The minimum fatal dose of the seed is unknown but a purgative doze of 3-4 seeds has been reported (Bouquet, 1969;Dazeil, 1937; Watt and Breyer-Brandwijk, 1962). Not much has been done in respect of its insecticidal properties. In Philippines, researchers at the Cotton Research and Development Institute used J. curcas seed oil to control bollworms. They also found that it successfully controls other pests such as weevils in stored grains. The seed powder is effective against snails that infest rice paddies (Solsoloy, 1995). Two new tinglain-type diterpene esters were isolated from the oil and phorbol ester extracted exhibited insecticidal activity against the larvae of Mcmduca sexta L. (Lepidoptera: Sphingidae) (Sauerwein, 1993). The leaves are burnt in houses as fumigant 20 University of Ghana http://ugspace.ug.edu.gh against bed bugs while powdered leaves have been used as repellent against house flies (Watt and Breyer-Brandwijk, 1962). In an experiment to determine the effect of Jatropha curcas oil on Sitophilus zeamais Motsch and Callosobruchus maculatus on stored maize and cowpea, respectively, Cobbinah and Appiah-Kwarteng (1991) showed that the oil of jatropha conferred similar level of protection to maize as neem, producing 36.5 % mortality in S. zeamais and mean percent grain damage of 2.17 as against 2.19 % by neem oil. He also showed that less than 1.0 % damage occurred in jatropha and neem treated beans; therefore, C. maculatus was highly susceptible to the oils. Application o f 5 % jatropha emulsion significantly reduced feeding activity by Z. variegatus by as much as 40 % within 24 hours after application. Treated insects were less mobile and were therefore more susceptible to predation (Cobbinah and Tuani, 1992). 21 University of Ghana http://ugspace.ug.edu.gh 3.0 MATERIALS AND METHODS. 3.1 Laboratory studies. Prior to the commencement of the laboratoiy work, visits were made to eggplant-growing areas in parts of Central Accra, to ascertain which insect pests were the most serious ones. Preliminary results showed that from the visits the eggplant skeletonizer, Selepa docilis, the fruit borer, Leucinodes orbonalis, Aphis gossypii', the lace bug, Urentius hystericellus among others caused serious damage to the eggplant (In line with reports in literature). Depending on their availability, the lace bug, the aphid and the eggplant skeletonizer, were used in the laboratory studies. Insects considered killed were the total number of insects apparently dead, moribund or so badly affected as to be unable to move a few steps when prodded. Normal or slightly affected insects were considered to have survived (Tattersfield et al., 1925). 3.1.1 Extraction of jatropha seed oil. The seeds of J. curcas were harvested from trees around Achimota in the Greater Accra Region o f Ghana in August 1999. They were sun-dried for 7 days after which they were shelled and batches were ground for 1 minute each into a fine powder, using IKA Universalmuhle M20 hand milling machine. Five hundred and fifty grammes of the powder and 2.5 litres of petroleum ether (40-60°C) were used in the extraction of the oil by Soxhlets apparatus for 48 h. This yielded about 260 ml of clean yellow oil. The ether was recovered through a rotary evaporator. 22 University of Ghana http://ugspace.ug.edu.gh 3.1.2 Preparation of aqueous seed extract of jatropha. Matured seeds were collected from jatropha trees around Achimota in the Greater Accra region of Ghana. They were sun-dried for 7 days aftter which they were shelled. The kernels were then pulverized into a fine powder using DCA Universalmuhle M20 hand milling machine. Five levels of the aqueous seed extract were prepared by weighing 2, 4, 6, 8, 10 grammes of the powder into conical flasks containing 100 ml each of water. These were shaken for two hours and left to stand for 48 h. They were then sieved and the resultant liquid used against the test insects. 3.1.3 Toxicity of jatropha aqueous seed extracts and oil to Aphis gossypii Aphis gossypii were collected from an eggplant field, which had not been chemically sprayed for several months. The insects were starved for 2 hr and used for the study. Ten nymphs of aphids each were placed into six petri dishes (9 cm in diameter) containing one young leaf each of aubergine taken from the apical shoot region which had previously been dipped into each of the various solutions (0, 2, 4, 6, 8,and 10 g/100 ml of water) for three seconds. Each treatment was replicated three times in a Completely Randomized Design (CRD) with a water treated control. Mortality was recorded after In a similar experiment, five levels of the seed oil of jatropha (0.1, 0.2, 0.3, 0.4, and 0.5 %) were prepared and 1 ml of 1 % soap solution (Teepol 610 S) was added as an emulsifier. Aphids were collected from the eggplant field as stated above (3.1.3) and were starved for 2 h. Ten nymphs each were placed into six petri dishes (9 cm in 23 University of Ghana http://ugspace.ug.edu.gh diameter) containing one young leaf each of aubergine taken from the apical shoot region, which had previously been dipped into the various solutions for 3 sec. There were three replications for each treatment arranged in a CRD. Mortality was recorded after 24 3.1.4 Toxicity of jatropha aqueous seed extract and oil to larva of Selepa docilis._ An aqueous extract of the seed was prepared as described in 3.1.2. Third instar larvae of S. docilis were collected from an eggplant field, which has not received chemical treatment for months and starved for two hours. Due to limited number of test insects, seven insects were placed in separate petri dishes (9 cm in diameter) containing a leaf each of eggplant that has previously been dipped into each of the various treatments for three seconds. Each treatment was replicated three times in a CRD. Mortality and percent leaf area damaged were recorded after 24 h. Survivors were also observed after this period to determine the effect of the extracts on the development of the larvae. Eight levels of the seed oil of jatropha (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8, %) were also prepared and 1ml of 1 % soap (Teepol 610 S) solution was added to each treatment as emulsifier. The experiment was set up as described in 3.1.4 above. Five insects per treatment were used mortality was recorded after 24h. The leaf area fed on by the surviving insects was also recorded during the period. 24 University of Ghana http://ugspace.ug.edu.gh 3.1.5 Effect of jatropha seed oil on the brinjal lace bug, Urentius hystericellus._ Six levels of the seed oil of jatropha (0.1, 0.2, 0.3, 0.4, 0.5, and 0.6%) were prepared as described in 3.1.4 Young leaves of eggplant were dipped into the various treatments for three seconds and placed individually into petri dishes (9 cm in diameter). There were three replications for each treatment. Newly developed adult lace bugs were collected from an eggplant field and starved for two hours. Eight bugs each were introduced into the petri dishes (9 cm in diameter) and each treatment was replicated three times. Mortality was recorded after 24 h. 3.1.6 Choice Bioassay Eggplant leaves (2 cm diameter) were dipped into an aqueous seed extract of jatropha (40 g/1) for three seconds. Each leaf was placed in a petri dish (9 cm in diameter) directly opposite a leaf previously dipped into water (control). This was replicated three times. There were two set-ups for two test insects; Urentius hystericellus and Selepa docilis. Ten adults of U. hystericellus and third instar S. docilis larvae were placed separately in the middle of each petri dish and their movement and settling was observed 15 minutes after their release. The numbers that settled on the treated and the untreated substrates as well as the percent leaf area damaged by S. docilis was recorded after 24 h. Mortality of test insects was also recorded over the period. The above experiment was repeated for V hystericellus using a filter paper. The paper was folded to give four equal sectors. Two opposite sides were impregnated with water whereas the other sides were treated with the aqueous seed extract. Ten adults of the test 25 University of Ghana http://ugspace.ug.edu.gh insects were released in the middle and the number that settled at each compartment after 24 h was recorded. A similar experiment was carried out using the two test insects and 0.4 % seed oil. The leaf dip method was used and ten insects were used in each case. There were three replicates and the number of insects that settled on the treated and untreated leaves, as well as the damage caused to the leaves was recorded after 24 h. 3.1.7 Effect of jatropha seed and neem products on S.docilis eggs. Neem aqueous seed extract was prepared after sun-drying the seeds for 7 days followed by shelling The seeds were ground into a fine powder by the method described in 3.1.2. Seventy five grammes of the powder was added to 1 litre of water and left to stand for 24 h. Jatropha aqueous seed extract was also prepared by weighing 40 g of the powder into 1 litre of water and left to stand for 48 h. These were sieved and the resultant solutions used for the experiment. Four leaves containing batches of S. docilis eggs were collected from the field and dipped into the seed extracts of jatropha and neem and placed separately in petri dishes (9 cm in diameter). The number of eggs that hatched and the survival of the neonate larvae on the treated food sources were recorded. 26 University of Ghana http://ugspace.ug.edu.gh 3.1.8 Effect of jatropha extract on the behaviour of Aphis gosssypii Two eggplant leaf discs (2 cm in diameter) were treated with 40 g/1 jatropha aqueous seed extract. Two others were dipped into water and placed alternately with jatropha- treated discs in a petri dish (9 cm in diameter). An adult aphid was released in the middle of the dish and its orientation to the leaves was monitored until it finally settled. The procedure was repeated four times. 3.2. Field studies. 3.2.1. Experimental site The work was carried out at the University of Ghana Farm, Legon between September 1998 and January 1999. The seeds of Black beauty, a cultivar of eggplant obtained from the Department of Crop Science, University of Ghana, were nursed and transplanted five weeks later in a Randomized Complete Block Design (RCBD). Five treatments, namely, Jatropha aqueous seed extract (JSKE), Jatropha seed oil (JSO), Neem aqueous seed extract (NSKE), Cymethoate 25EC (CY) and Control (NS) were used. There were four blocks (replicates) with each block containing each of the five treatments. The size of each plot in a block was 3 x 5 m and separated from each other by 1.5 m path. Each plot had three rows containing five plants spaced at 1 x 1 m. This gave a plant population of 10,000 per hectare. Routine cultural practices such as weeding, fertilizer application and irrigation were carried out when necessary. 27 University of Ghana http://ugspace.ug.edu.gh Based on the results of laboratory experiments, 40 g/1 and 4 ml/1 of the aqueous extract and the seed oil of jatropha, respectively, were used. For neem and cymethoate, the recommended rates of 75 g/1 (Owusu-Ansah et al., 1998) and 2 ml/1, respectively, were applied using a CP 15 knapsack sprayer. Weekly application of these treatments began four weeks after transplanting, during which a spray liquid of 1 litre per plot was used for the next four weeks thereafter, 1.5 litres per plot was used to correspond with higher vegetative growth. All treatments were applied in the mornings. 3.2.2 Data Collection The following data were collected. -The number of days to first flowering, -The number of days to first fruit maturity, -The number of fruits per plant, -Plant height at flowering, -Fruit weight, -The number of bored fruits, -Insects associated with the treatments, -% Leaf area damaged by leaf feeding insects, -Fruit yield, -Beneficial arthropods. Sampling for insects started at the nursery. In the field, this was done a day before spraying, one day after spraying and 3 days thereafter between the hours of 0530 and 28 University of Ghana http://ugspace.ug.edu.gh 0730 GMT. Three plants were selected for each treatment, three leaves per plant were randomly examined, and all insects found were recorded. The immature stages were cultured in the Entomology laboratory of Crop Science Department until adult emergence. Harvested Suits were cut open to assess fruit borer attack. Fruit yield was calculated based on mean yield per plant, spacing and plot size. 3.2.3 Data analysis All count data on the major insect pests and yield indices were transformed using the square root transformation, ((V x) or (V x + 0.5)) where there were zeros, before analysis, statistically. Where significant differences were observed, means were separated using the Least Significant Difference (LSD). Correlation analysis was also carried out between yield of marketable fruits and number of fruits per plant. Probit analysis was used to determine the LD50 and LD90 of the plant products for the tests insects used in the laboratory bioassay. University of Ghana http://ugspace.ug.edu.gh Pr ob it 6.5 6 5.5 y, =2.4006x+ 1.7645 r2 = 0.9432. 4.5 4 1.2 1.4 1.6 1.8 2 Log. Concentration (g/l) Fig. 1 Response of S. docilis(y^) and A. gossypii (y2) to varying levels of jatropha (aq) seed extract 2.2 31 University of Ghana http://ugspace.ug.edu.gh Pr ob it. Log. Concentraion (ml/I). Fig. 2 Responses of S. docilis (y-i) and A. gossypii (y2) to varying levels of jatropha seed oil. 32 University of Ghana http://ugspace.ug.edu.gh Pr ob it Log, Concentration (ml/l) Fig.3 Respose of U. hystericellus to varying levels of jatropha seed oil. 33 University of Ghana http://ugspace.ug.edu.gh Plate 1 shows percent leaf area consumed by the surviving larvae of Selepa docilis following treatment of the leaves with varying levels of the seed extract. The larvae consumed more than 90% of the leaf area within 24 hours in the control and just less than 1 % leaf area consumption in the 20 g/1 seed extract treatment. Those in the other treatments did not feed at all. They were either dead or moribund within the period. Plate 1. Feeding patterns of larvae S. docilis on aubergine leaves treated with seed extracts of jatropha after 24 h. Corresponding % leaf area consumed is as follows: 0 = 90-95, 20 = 0.5-1.0, 40,60, 80,100 = 0. 34 University of Ghana http://ugspace.ug.edu.gh In the oil treatment, about 60% leaf area was consumed in the control within 24 hours and 100 % within 48 hours compared to between 10-20 % leaf area consumption at a concentration of 0. l%.oil within 24 h. There was no feeding at the concentrations of 2-8 ml/1 within the period (Table 2). Some of these insects died after 24 hours of exposure but those alive after the period became moribund and died 48 h later. Table 2. Feeding effect of jatropha seed oil on larvae of S. docilis Treatment (m/T) % leaf area da map* 0 60-65 1 10-20 2 Nil 3 Nil 4 NU 5 NU 6 Nil 7 NH 8 NU 4.1.3 Effect of jatropha seed oU on the lace bug, U. hystericellus. The effect of the oil on the insect is shown in Appendix 12. When the concentration was increased from 1 to 2 ml/1, mortality increased from 8.4 to approximately 42 % but as the concentration was increased from 5 to 6 ml/1, mortality remained constant at 62.5 %. Figure 3 shows the response of adult U. hystericellus to varying levels of jatropha seed oil. Fifty percent (LD50) and 90 % (LD9o) mortalities corresponded to 0.55 and 1.17, respectively. 35 University of Ghana http://ugspace.ug.edu.gh 4.1.4 Choice bioassay Plates 2, 3, and 4 show the results of the choice bioassay. Ninety percent of U. hystericellus settled on the untreated surface whereas 10 % settled on the treated surface, (Plate 2). In the case of S. docilis, 60 % settled on the untreated leaf causing about 30 % leaf area damage compared to 40 % settling on the treated leaf. About 50 % of the insects, which settled on treated surface died and caused less than 5 % leaf area damage (Plate 3). In the case of the oil, 40 % settled on the untreated and 60 % (all dead) settled on the treated. There was about 20 % leaf area damaged in the control as against no feeding in the treated leaf, (Plate 3). The feeding pattern of the larvae of S. docilis on aubergine leaves treated with jatropha seed extract, seed oil and water is shown in Plate 4. Plate 2. Preference for treated (T) and untreated (UT) portions of filter paper by U. hystericellus (black spots). T. = One insect, UT. = Nine insects. 36 University of Ghana http://ugspace.ug.edu.gh Plate 3. Preference for treated (T) and untreated (UT) leaves; A, (aq); and B, (oil) of jatropha seed by S. docilis larvae, (aq), T = 4 and UT = 6 insects. (oil), T = 6 (all dead) and UT = 4 insects. I A B C Plate 4. Comparison of the feeding patterns by the larvae of S. docilis on aubergine leaves treated with A, aqueous seed extract; B, water; and C, seed oil. after 24 h. 37 University of Ghana http://ugspace.ug.edu.gh Plate 3. Preference for treated (T) and untreated (UT) leaves; A, (aq); and B, (oil) of jatropha seed by S. docilis larvae, (aq), T = 4 and UT = 6 insects. (oil), T = 6 (all dead) and UT = 4 insects. I A B C Plate 4. Comparison of the feeding patterns by the larvae of S. docilis on aubergine leaves treated with A, aqueous seed extract; B, water; and C, seed oil. after 24 h. 37 University of Ghana http://ugspace.ug.edu.gh 4.1.5 Effect of jatropha and neem products on S. docilis eggs. Table 3 shows the effects of the various treatments on the oviposition of S. docilis. There was 100 % hatchability in all the treatments except in jatropha seed oil treatment where there was a reduction by 21 %. With the exception of the control in which there was 74 % survival of the neonate larvae, 100 % mortality was recorded in the other treatments after 48 h. Table 3. Effect of jatropha seed extract, jatropha seed oil, and neem seed extract on S. docilis eggs. Treatment No. of eggs No. hatching No. alive after 24 h No. alive after 48 h. Water control 31 31 31 23 Jatropha seed 14 14 14 0 extract (40 g/1) Neem seed 26 26 26 0 extract (75 g/1) Jatropha seed 38 30 30 0 Oil (0.4%) 4.1.6. Effect of jatropha extract on the behaviour of Aphis gossypii. Plate 5 shows the orientation of A. gossypii to treated (40g/l seed extract of jatropha) and untreated leaf discs. The insect moved from the point of introduction to the untreated leaf disc, then back to the treated. It then turned round and moved to the point of introduction and settled finally on the untreated in 42 minutes. 38 University of Ghana http://ugspace.ug.edu.gh Plate 5. Orientation of A. gossypii to treated (T) and untreated (UT) leaf discs 4.2 Field work. A list of insects recorded during the sampling period and their relative abundance in the various treatments is given in Tables 4 and 5. These are leaf feeders flower bud and Suit borers, terminal bud and apical shoot feeders. The cotton jassid, Empoasca lybidk ; the eggplant skeletonizer, Selepa docilis; the brinjal lace bug, Urentius hystericellus-, white flies, Bemisia tabaci; the fruit borer, Leucinodes orbonalis-, Thrips palmi-, and Tetranychus sp were recorded in high numbers. They caused varying degree of damage to the plants in the various treatments Plates (6 to 16). 39 University of Ghana http://ugspace.ug.edu.gh Table 4. A list of insects recorded on eggplant (Solatium melongena L.) at the University Farm, Legon. Scientific name Order Family Part of plant found Empoasca lybica de Berg. Homoptera Cicadellidae Leaves Selepa docilis Butler Lepidoptera Noctuidae Leaves Urentius hystericellus Richter Heteroptera Tingidae Leaves Bemisia tabaci Genn. Homoptera Aleyrodidae Leaves Aphis gossypii Glover Homoptera Aphididae Leaves Prodenia litura Koch Lepidoptera Noctuidae Leaves Eublema admota Fldr. Lepidoptera Noctuidae Terminal leaf Scrobipalpa blapsigona Meyrick Lepidoptera Gelechidae Flower buds Thrips palmi Kamy Thysanoptera Thripidae Leaves,flowers Epilachna elaterii Rossi Coleoptera Coccinellidae Leaves Zonocerus variegates L. Orthoptera Pyrgomorphidae Leaves Leucinodes orbonalis Guen Lepidoptera Pyralidae Fruit Anoplocnemis curvipes Fab. Heteroptera Coreidae Apical shoot Dysdercus superstitiosus Fab. Heteroptera Pyrrhocoridae Leaves Corynasp. Coleoptera Meloidae Leaves Tetranychus sp. Acarina Tetranychidae Stem, leaves Unidentified Diptera 40 University of Ghana http://ugspace.ug.edu.gh Table 5. Relative abundance of insects collected from S. melongena under the various treatments at the University farm, Legon. Scientific/Common name JSKE JSO NSKE CY NS Empoasca lybicus 213 355 108 118 602 Selepa docilis 25 117 35 1 174 Urentius hystericellus 2 174 2 26 1429 Bemisia tabaci 79 92 25 636 2351 Spider 4 4 4 3 1 Crematogaster sp 1 1 1 0 2 Aphis gossypii 27 8 3 0 35 Prodenia litura 0 8 0 0 3 Scrobipalpa blapsigona 34 71 59 32 96 Thrips palmi 29 48 51 223 40 Epilachna elaterii 0 0 0 2 2 Zonocerus variegatus 2 6 0 5 1 Anoplocnemis curvipes 12 5 0 0 27 Lagria cuprina 0 1 1 1 0 Eublema admota 0 5 0 0 2 Mantis mantis 2 5 8 2 2 Dysdercus superstitiosus 6 4 7 3 4 Tetranychus sp 240 109 1110 0 1746 Nezera viridula 1 3 4 5 14 JSKE: Jatropha seed kernel extract JSO: Jatropha seed oil. NSKE: Neem seed kernel extract. CY: Cymethoate NS: No spray 41 University of Ghana http://ugspace.ug.edu.gh Plate 6. Damage to plant caused by larvae o f S. docilis Plate 7. Adult S. docilis 42 University of Ghana http://ugspace.ug.edu.gh Plate 8. Damage by larvae of E. aclmota Plate 9. Adult E. admota 43 University of Ghana http://ugspace.ug.edu.gh Plate 10. Chlorotic leaf surface caused by Tetranychus sp. infestation. University of Ghana http://ugspace.ug.edu.gh Plate 12. Adult o f fruit and shoot borer, L. orbonalis Plate 13. Larvae of the fruit and shoot borer, L. orbonalis University of Ghana http://ugspace.ug.edu.gh 1 Kl ! ! BOR I K D AM -\( il Plate 14. Tunnels created in the fruits by emerging larvae of L. orbonalis Plate 15 Internal damage caused to the fruit by larvae of L. orbonalis 46 University of Ghana http://ugspace.ug.edu.gh Plate 16. Unidentified parasitoid associated with the larvae of S. docilis showing the pupal case. Figures. 4, 5 and 6 represent the population trends of E. lybica, S. docilis and U. hystericellus, respectively. There was generally a gradual build up of the insects’ populations four weeks after sowing until a peak was attained around the sixth and the seventh week before declining to zero at the twelfth week. Cymethoate treatment generally performed better than the other treatments as lower number of these insects were collected from that plot. Figure 7 shows significant (P < 0.01) correlation between number of fruits and yield in tonnes/h. 47 University of Ghana http://ugspace.ug.edu.gh Nu mb er of ins ec ts Weeks after transplanting. Fig. 4 Population trend of E. LybicO' on treated eggplant 48 University of Ghana http://ugspace.ug.edu.gh Nu mb er of ins ec ts 40 n 35 - 30 - 25 20 15 10 5 - 0 » 1 10 11 12 Weeks after transplanting. Fig. 5 Population trend of S. docilis on treated eggplants 49 University of Ghana http://ugspace.ug.edu.gh Nu mb er of ins ec ts Weeks after transplanting Fig.6 Population trend of U. hystericellus on treated eggplant — NSKE -a -JS K E JSO - * - C Y - * - N S 50 University of Ghana http://ugspace.ug.edu.gh Nu mb er of fru its per p lan t. 4.5 3.5 2.5 1.5 0.5 10 12 Yield in tonnes per hectare. Fig. 7 Correlation between Yield in tonnes per hectare and No. of marketable fruits per plant. 51 University of Ghana http://ugspace.ug.edu.gh Tables 6 shows the means of growth and yield indices as well as the effect of some of the insect pests on these indices. The number of bored buds ranged from a mean of 9.25 for cymethoate to 24.0 for control. There was no significant difference (P=0.05) between the treatments. The number of holes in fruits also ranged from 1.75 for cymethoate to 30.50 for control. The control plot differed significantly (P < 0.05) from the other treatments. The values for the plant products ranged from 3.25 for neem extract to 12.75 for jatropha oil. There were no significant differences (P= 0.05) among these treatments. The percentage of fruits bored also followed the same pattern with as high as 40 % recorded for control as against 4 % for cymethoate. The damage in plants treated with neem and jatropha products ranged between 6-11 %. The control pot differed significantly (P < 0.01) from other treatments. Chlorosis of leaves was significantly (P < 0.01) higher for plants treated with Jatropha seed oil and control (25-29 %) compared to those treated cymethoate and neem extracts (0.3-7.5%). (Table 7) Damage by leaf feeders was significantly (P < 0.05) lower for plants that received chemical treatments (19-22%) than for control where as much as 30% leaf defoliation was recorded. (Table 8). Plant height at flowering ranged from 31.7 cm. for plants treated with cymethoate to 41.8 cm for those treated with jatropha seed oil (Table 9). There were no significant differences (P = 0.05) between the treatments. The control plot recorded significantly (P <0.05) lower figures in number of fruits per plant, marketable fruit weight, fruits weight 52 University of Ghana http://ugspace.ug.edu.gh per plant and yield in tonnes per hectare compared to the other treatments while plants treated with jatropha seed oil recorded highest values in all the indices (Table 10). Significantly (P < 0.05) higher number of thrips was recorded on cymethoate treated plot compared to the others. This ranged from 35 insects for cymethoate to 8 for jatropha aqueous seed extract treated plot (Table 11). Higher number of thrips (18) were collected at noon than other times of the day where the relative humidity and temperature were 55.2 % and 41.1 °C, respectively, (Table 12). Table 6. Effect of treatments on damage caused to the fruits of S. melongena. Treatment No. of flower buds bored. No. of holes in fruits. % bored fruits NSKE 14.00 ± 3.58 a 3.25 ± 1.65 a 6.26± 0.99 a JSKE 13.75+4.50a 9.25 ± 5.94a 11.86 ± 3.59 a JSO 22.00 ± 4.30a 12.75 ± 8.48 ab 9.60 ±1.09a CY 9.25 ±3.33 “ 1.75 ±1.11a 4.28 ± 1.46 a NS 24.00 ± 9.04 “ 30.50 ± 10.41 b 40.14 ± 8.19 b Means in a column followed by the same letters in a column do not differ significantly from one another at P = 0.05. Key: JSKE, Jatropha seed kernel extract; JSO, Jatropha seed oil; NSKE, Neem seed kernel extract; CY, Cymethoate; NS, No spray. 53 University of Ghana http://ugspace.ug.edu.gh Table 7 Effect of treatments on chlorotic leaf damage, % leaf defoliation and plant height. Treatment % leaf chlorosis. % defoliation. Plant height, (cm.) (X ± SE) (X + SE) (X + SE) NSKE 7.50 ± 5.37ab 20.30 ± 0.65 a 37.20 + 6.52a JSKE 12.10 ± 4.42 bc 21.13 + 1 .3 2 a 34.30 ± 2.52 a JSO 25.80 ± 8.06 22.52 ± 2.25 a 41.80 ± 5.36 a CY 0.30 + 0.20a 19.52 +0.25 a 31.70+ 1.82 a NS 29.60 + 7.56 d 30.04 +4.86 b 37.50 + 3 .4 9 a Means followed by the same letters do not differ significantly from one another at P = 0.05. Table 8 Effect of treatments on yield of eggplant. Treatment Marketable fruit weight. Marketable fruit wt./plant. Fruit no. per plant. Yield Tonnes/ha. NSKE 240.38 ± 8.70 b 912.78 ± 135.61 b 4.03 + 0.50b 9.13 ±1.35b JSKE 227.23 ± 9.99 b 864.92 ± 102.47 b 4.15 + 0.56b 8.65 + 1.02b JSO 266.20 ± 16.59 b 985.00 +40.85 b 4.23+ 1.53b 9.85 +3.32b CY 224.22+ 10.06 b 873.01 +172.66 b 4.15 + 0.97b 8.73 + 1.73b NS 187.45±22.19a 114.82 ± 25.16a 1.05 ± 0.23a 1.14±0.25a Means in a column followed by the same letters in a column do not differ significantly from one another at P = 0.05 Key: JSKE, Jatropha seed kernel extract; JSO, Jatropha seed oil; NSKE, Neem seed kernel extract; CY, Cymethoate; NS, No spray. 54 University of Ghana http://ugspace.ug.edu.gh Table 9.Effect of treatments on number of thrips. Treatment No. of thrips. NSKE 8.75 ± 4.37a JSKE 8 .0 0 ±2.08 3 JSO 12.00 ± 3 .0 0 “ CY 35.25 ± 10.59 b NS 9.75 ± 0.85 a Means followed by the same letters do not differ significantly from one another at P = 0.05. Key: JSKE, Jatropha seed kernel extract; JSO, Jatropha seed oil; NSKE, Neem seed kernel extract; CY, Cymethoate; NS, No spray. Table 10 Number of thrips recorded for NS at different times of the day. Time (Hours) Average no. of thrips Relative humidity (%) Average temperature (°C) 6.00-7.00 12 95.3 27.0 12 .0 0 -1.00 18 55.2 41.1 5.00-6.00 13 80.1 31.2 University of Ghana http://ugspace.ug.edu.gh 5.1 Laboratory bioassays The studies showed that 42.9 and 80 % mortalities were induced in S. docilis larvae when exposed to 2 0 and 60 g/1, respectively, of jatropha seed aqueous extract while 100 g/1 induced a mortality of 95.7 %. When these same concentrations were administered to A. gossypii, 36.6, 6 6 .6 and 93.3 % mortalities, respectively, were observed. Also fifty percent and ninety percent lethal doses (LD50) and (LD90) of 22.3 g/1 and 76.0 g/1, respectively, were obtained for S. docilis while those of A. gossypii were 28.4 and 85.1 g/1, respectively. These showed that S. docilis larvae were more susceptible to the aqueous extracts than A. gossypii. A possible explanation to this is that the larvae being a herbivore is more likely to have ingested much of the extract which may lead to stomach poisoning compared to A gossypii which is a sap sucker and whose mortality depends on contact and/or systemic effect (which is yet to be established) of aqueous seed extract of jatropha. The LD50 values are quite low compared to what is generally recommended for neem seed extract (50-75 g/1) for the control of insect pests in Ghana (Owusu-Ansah et al., 1998; Issahak, 1998). It is important to indicate that it is much easy to reach and collect the seeds of jatropha than those of neem and, therefore, makes the use of jatropha more economical in terms of labour compared to neem. 5.0 DISCUSSION The feeding effect o f S. docilis larvae on aubergine leaves treated with aqueous seed extract of jatropha showed that when leaves were treated with 2 0 g/1, a feeding deterrent of about 56 University of Ghana http://ugspace.ug.edu.gh 90 % was observed. About 57 % of the larvae died within 48 h. while 74 % died within 72 h. There was, however total feeding inhibition on leaves treated with higher concentration of 40-100 g/1. Butanol extract of J. curcas has been shown to have a high insecticidal and antifeedant activity against 3rd instar-larvae of Atteva fabriciella. Swed (Neelu et al., 1997). After the 24 h. of exposure, however, all the larvae became moribund. Under field conditions, therefore, they would be highly susceptible to predation. The larvae, however, died 48 h. after exposure to the treated leaves. Death of the larvae may be due to contact poisoning, starvation, or both. Methanol extract of jatropha has been shown to be a potent antifeedant against the teak skeletonizer, Eutectona machaeralis Walk. (Lepidoptera: Pyralidae) (Meshram et al., 1994). Cobbinah and Tuani (1992) showed a decrease in the activity of Z. variegatus when treated with 5 % emulsion of Jatropha curcas. Those on water-treated control consumed all the leaves within 48 and h. later developed into adults. Jatropha seed oil treatment also showed similar responses. When A. gossypii, S. docilis and U. hystericellus were exposed to aubergine leaves treated with 1 ml/1 seed oil, 33.3, 12.0 and 8.4 % mortalities, respectively, were observed but mortalities increased to 46.7, 92.5,and 46.9 % when 3 ml/1 was applied. At 5 ml/1, however, 86.7, 100 and 62.5 % mortalities were observed in the test insects. These figures indicate that at low concentrations, S. docilis and U. hystericellus appeared to be least affected by the oil but as concentration increased, S. docilis became more susceptible to the oil while U. hystericellus does not seem to be very much affected. This could be due the sap sucking nature of U hystericellus, which may not have picked up enough of the ai compared to S. docilis, which is a herbivore. 57 University of Ghana http://ugspace.ug.edu.gh The slopes of the response curves are in the increasing order of U. hystericellus (2. 08) < A. gossypii (2.11) < S. docilis (3.15). The LD50 for S. docilis, A. gossypii and U. hstericellus were 1.5, 2.2 and 3.6 ml/1, respectively, while their respective LD90 values were 3.7, 8.7 and 14.7 ml/1. These figures show that to produce 50 % mortality, the oil was 2.4 times and 1.5 times more toxic to S. docilis than to U. hystericellus and A. gossypii, respectively, while at 90 % mortality, these figures increased to approximately 4 times and 2 times, respectively. Among the three insects tested, S. docilis was most susceptible to the seed oil while U. hystericellus was least susceptible. This may partly explain the reason why about 10-20 % leaf defoliation was observed in S. docilis larvae placed on aubergine leaves treated with 0.1 % oil as compared to over 60 % leaf area consumption in the control (Table 2). Those that fed on leaves treated with 0.1 % oil failed to reach the adult stage. This suggests that the oil may have led to stomach poisoning and/or interfered with the production of hormones involved in metamorphosis. Deyer et al., (1986) reported that neem kenel powder and cake inhibits the development of 3rd instar larvae of S. docilis. Also, concentrations of 0.2-0.8 % deterred feeding by S. docilis larvae by 100 %. They appeared slow in activity and are, therefore, likely to be predisposed to predators under field conditions. They all died within 48 h. probably due to starvation or contact poisoning or both. In the choice bioassay, approximately the same number of U. hystericellus (1 0 %) settled on leaves or filter paper treated with jatropha seed extract as against 90 % on water-treated 58 University of Ghana http://ugspace.ug.edu.gh control This suggests that the seed extract is more effective to U. hystericellus as a strong repellant than as a toxicant. Selepa docilis larvae also showed similar responses to leaves treated with the aqueous extract and oil. Though a higher number settled on treated leaves, feeding inhibition and death of insects occurred during the exposure time. The insect is, therefore, more likely to avoid plants treated with the extracts in the field. With regards to leaves treated with the aqueous seed extract, a greater number of the insects (60 %) preferred the untreated leaves compared to treated ones suggesting the repellency effect of the aqueous extract. Feeding deterrence was also observed in insects that settled on the treated leaves. Aqueous seed products of neem and jatropha did not affect hatchability of eggs of S. docilis but there was 21 % reduction in hatchability when the eggs were treated with 4 m/1 seed oil. All the neonate larvae that hatched out could not survive on the treated leaves but died within 48 h indicating that the plant products have a strong larvicidal effect on the first instar larvae of of S. docilis. The response of A. gossypii to treated and untreated aubergine leaf discs, (Plate 5), shows random movements of the insect in the petri dish containing the leaf discs. The insect however, after moving round for about 42 minutes, settled on the untreated leaf disc. Though there was orientation towards both types of leaf discs, its final settlement on the untreated disc suggests that jatropha extracts could serve as a good repellent to the insect. Application of jatropha aqueous seed extract and seed oil in the field could protect a University of Ghana http://ugspace.ug.edu.gh growing crop in two ways. First, the crop would be protected via a primary gustatory repellent action of the products, which the insects ingest in an attempt to feed on the foliage. Secondly, the insect picking up residues on sprayed foliage or through foraging behavior can suffer feeding inhibition and high mortality, which may result in reduced crop damage. During insect pests outbreaks, farmers are often helpless and have to rely on Governments to organize and effect control, which are usually late. The availability and the exploitation of jatropha under such conditions could enable the farmer to reduce spread and damage to crops. Arguably, control may not be achieved through the use of jatropha alone, but reasonable level of protecting the crop could be ensured. 5.2 Field work 5.2.1 Insect pests encountered in the nursery. The first insect to be encountered in the nursery was the cotton jassid; Empoasca lybica. This was found a week after the seedlings emerged. They were widespread and sucked sap from the plants. Also observed were Aphis gossypii and Selepa docilis. The aphids were found on the stems of plants while S. docilis were found causing slight defoliation of the leaves. Their egg masses were deposited on the edges of leaves. A week after transplanting, however, all these insects disappeared. This may be due to the transplanting stress as the weather was so dry at the time. 5.2.2 Insect pests encountered in the field Table 4 shows a list of insects encountered in the field. They belong to six orders, twelve 60 University of Ghana http://ugspace.ug.edu.gh families and eighteen genera. Three weeks after transplanting, it was observed that the cotton jassid, Empoasca lybica (Homoptera: Cicadellidae); the eggplant skeletonizer, Selepa docilis (Lepidoptera: Noctuidae); the brinjal lace bug, Urentius hysterycellus (Homoptera: Tingidae); white flies, Bemisia tabaci (Homoptera: Aleyrodidae); ants and spiders were randomly distributed in all the treatments The population trend of E. lybica on the various treatments is shown in Fig. 4. There was a gradual increase in numbers from the fourth week up to about the seventh week after sowing before falling to zero in the twelfth week. Both the nymphs and the adults were found on the upper and the lower surfaces of leaves. They are known to suck sap from the under surfaces of maturing leaves and secreting toxic saliva which causes the leaves to turn yellow and brown and die (Chritchley, 1997). Severe infestation reduces yield as chlorosis of the leaf reduces the amount of chlorophyll necessary for photosynthesis. Even though no statistical analysis was done on their relative abundance in the various treatments, highest numbers were observed in the control plot; an average of 42 insects per visit while the lowest number was observed with the cymethoate and NSKE treatment with an average of 9 insects per visit. The low numbers associated with neem might be due to its repellency effects (Schmutterer, 1990). Also Heyde et al., (1984) showed that settling by the brown planthopper, Nilaparvata lugens and the Sogatella furcifera was progressively reduced by increasing concentration of neem oil from (1 to 50%). Nilaparvata. lugens failed to produce the courtship signals after topical application of 30% neem oil (Saxena et 61 University of Ghana http://ugspace.ug.edu.gh al., 1993). Asari and Nair (1972) demonstrated the repellent effect of a ten-day interval spraying of NSKE (10 g/1) on brinjal against Empoasca spp. Cymethoate on the other hand has both systemic and contact properties, hence the relatively low number of jassids found on eggplants treated with the insecticide The egg masses of Selepa docilis were found to be deposited at the edges of leaf surfaces of plants in all the treatments. The larvae that hatched out caused serious defoliation of the leaves especially in the control plot (Plate 6 ). Though there were no significant differences (P=0.05) between the botanicals and cymethoate, the control differed significantly (P < 0.01) from other treatments, (Table 7). Frimpong (1981) stated that the insect causes serious defoliation of the leaves and its attack could result in stunted and withered plants. Fig. 5 shows the population trend of S. docilis over the period of sampling. The population peaked between the fifth and the ninth week after transplanting. This was just around the flowering period. Selepa. docilis were probably attracted to the colour of eggplant flowers (Southwood, 1978). It was observed, however, that as the plant ages, the insect population declined considerably even with the control. The decline in the population around the 12th week could be due to the fact that the plants had used most of the stored food substances in the reproductive phase and were not able to adequately supply the needs of the insects’ population. Nsowah (1969) showed that 70% of total yield in brinjal are produced during the first eight to nine weeks after transplanting. This might be partly responsible for the high numbers of the insect encountered between 5 and 10 weeks after planting. Veeravel and 62 University of Ghana http://ugspace.ug.edu.gh Baskaren (1995) showed that maximum pest population occurred in brinjal during the flowering and bearing stages o f the plants. However, during the senescence stage, pest population was lowest. High numbers were found on the control plot, whereas very low numbers were observed especially in the cymethoate and jatropha aqueous seed extract treatments. The low numbers of the insect associated with the aqueous extracts of jatropha treatment confirms the results obtained in the laboratory bioassays which showed that eggplant leaves treated with 40 g/1 and 0 .2 % seed extracts and oil, respectively, inhibited feeding by the larvae of S. dicilis. Cobbinah and Tuani (1992) showed that application of 5 % emulsion of jatropha to eggplants reduced the feeding activity of Z. variegatus by 40 % within 24 hrs. Neem oil applied to eggplants at 5-20 % effectively controlled S. docilis with the 10 % concentration causing instant mortality (Cobbinah and Osei-Owusu, 1988) Even though there were high deposits of egg masses in all plots most of the larvae that hatched out could not survive on the treated plants compared to the control, (Plate 6 ). This observation confirms the result of laboratory studies carried out to determine the ovicidal effect of the plant products on the insect. The brinjal lace bug (Urentius hystericellus) recorded the second highest in numbers after the red spider mite Tetrcmychus sp. There was heavy infestation in the control plots while relatively low numbers were encountered in jatropha extracts, neem extract and cymethoate 63 University of Ghana http://ugspace.ug.edu.gh treatments (Fig. 6). With age of the plants, however, their numbers declined. Cobbinah and Osei-Owusu (1988) showed that application of 5-20 % neem oil on brinjal strongly repelled Urentius sp from treated plants. The laboratory bioassays showed that about 90 % of the insects preferred untreated plants to those treated with 40 g/1 of jatropha aqueous seed extract. Also 0.36 % oil produced about 50 % mortality in the insects (Fig. 3). Both the nymphs and the adults were found in clusters at the under surfaces of the leaves although occasionally the adults were found on the upper surfaces as well. Leaves attacked by U. hystericellus showed chlorotic symptoms which latter turned brown and dropped off (Plate 11). This insect has also been reported to be a very serious pest of local garden egg Solatium integrifolium L (Brempong-Yeboah and Okoampa, 1989) but is effectively controlled using Dimethoate 20 EC at 80 g /ha. Attack by the bud borer, Scrobipalpa blapsigona (Lepidoptera: Noctuidae) was manifested in the buds infested by the larvae, which showed slight differences even though there were no significant differences among the treatments (Table 6 ). It could, however, be observed that the lowest numbers occurred on the cymethoate treated plants. This may be due to its systemic effect. The buds, once infested, were aborted. Attack by, L. orbonalis was observed in all the treatments. There were significant differences (P < 0.05) and (P < 0.01) among treatments in the number of holes in the fruits and percent bored fruits, respectively, (Table 6). Jatropha seed oil is effective against cotton 64 University of Ghana http://ugspace.ug.edu.gh bollworms (Solsoloy, 1995). Neem extracts have been used successfully to control major insects attacking vegetables (Owusu-Ansah et al., 1998). Both the neem and cymethoate differed significantly (P < 0.05) from the control in terms of number of holes bored into the fruits but there were no significant differences (P=0.05) between jatropha aquoeus seed extract and the oil from the control. The mature larvae of L. orbonalis emerging from the fruits to pupate created the holes observed in the fruits. Therefore, the systemic effects of neem (Jacobson, 1989) and cymethoate might have affected their survival and development. Only a few of them were, therefore, able to emerge from the fruits to pupate hence fewer numbers of holes recorded for these treatments. This means that with time fewer and fewer number of the adults will be present in the system below the economic threshold. Chowdhury et al., (1993) showed that cypennethrin 10 EC is very effective against the fruit borer. Jaropha extracts and the oil on the other hand might not have conferred this systemic property on the plant and therefore the relatively high number of holes that were recorded in those treatments. This implied that majority of the larvae were likely to complete their life cycle leading to increased number of the insect in the system. The botanicals compared favourably with the synthetic insecticide in protecting the fruits against damage by the borer (Table 6). The neem seed extract, jatropha seed extract and jatropha seed oil provided 85, 70 and 77.5 % protection, respectively, against the fruit and shoot borer (Table 6 ). The 40 % damage on the untreated plants fell within the range of 30- 65 University of Ghana http://ugspace.ug.edu.gh 50 % reported by Mishra and Mishra (1996). The leafworm, Eublema admota (Lepidoptera: Noctuidae) fed on young leaves especially soon after transplanting. It also webbed together young leaves (Plate 8). This activity could greatly affect the photosynthetic activity of the young growing plant and therefore the ultimate yield. Its incidence was quite high soon after transplanting but as the plant puts on more vegetation, their numbers fell drastically to insignificant levels. According to Norman (1974), these insects are generally not present in high numbers to be considered as serious pests. Hence hand picking of the larvae could serve as an effective control measure. Thrips palmi (Thysanoptera: Thripidae) was first observed in the cymethoate treated plants which also recorded the highest number of the insect while lowest numbers were collected from the plants treated with NSKE probably due to its repellency effect. (Table 5). There were significant differences (P < 0.05) between the treatments (Table 9). This shows that the insect may be developing some form of resistance to the synthetic insecticide. Cermeli et al., (1993) showed that out of eleven insecticides tested in an experiment, high tolerance to the chemicals was observed. Etienne et al., (1990) also found that synthetic insecticides used in controlling insect pests of aubergine led to the reduction of the activity of predators thus leading to higher population of T. palmi in treated areas than untreated ones. It was also observed that the insect was more commonly found during hot afternoons with average temperatures and relative humidity of 41.1 °C and 55.5 %, respectively, on surfaces of leaves than other times of the day (Table 10). This may be one of the reasons they are a 66 University of Ghana http://ugspace.ug.edu.gh problem in green houses. Whiteflies, Bemisia tabaci (Homoptera: Aleyrodidae) were also observed in very high numbers in the control while lower numbers were associated with plants treated with jatropha and neem extracts (Table 5). They were normally found in clusters on the lower surfaces of older leaves. They sucked sap from the underside and secreted honey due that led to the growth of sooty mold on the upper surfaces of leaves. Most of the plants on which the insects were found were observed to develop symptoms associated with viral infection. The insect is a vector of leaf curl and mosaic viral diseases (Chritchley, 1997). The red spider mite, Tetranychus sp first appeared in high numbers in the neem treatment and the control plots in the eleventh week after sowing and a week later to other treatments except cymethoate where the insect was not found (Table 5). The high infestation led to serious chlorosis of affected leaves (Plates 10). Even though there were differences among treatments in terms of numbers, it could be observed that none of the botanicals was effective against the mite. Its high incidence, however, had little effect on the yield as its infestation occurred rather late in the experiment. Other insects such as Anoplocnemis curvipes (Heteroptera: Coreidae); Zonocerus variegatus c '\': f / 67 University of Ghana http://ugspace.ug.edu.gh (Orthoptera, Pyrgomorphidae); Prodenia Jitura (Lepidoptera: Noctuidae); Aphis gossypii (Homoptera: Aphididae) among others were also encountered but may not be considered very important based on the numbers observed, (Table 5). Neem and jatropha extracts have been shown to strongly repel Z. variegatus, and A. gossypii. (Cobbinah and Osei-Owusu, 1988). 5.2.3 Beneficial arthropods Members in this group were not found in high numbers. Those encountered included spiders, ants, Crematogaster sp (Hymenoptera: Formicidae); the lady beetle, Epilachna elaterii (Coleoptera: Coccinelidae) Mantis mantis (Dicrtyoptera: Mantidae) and some unidentified dipterans (Plate 16). The dipteran was found associated with the larvae of S. docilis. One special feature about it is that the pupa develops in a thick white cocoon, and this might provide a good protection against insecticides. Most of the cocoons collected from the field gave rise to adult insects (Plate 16). The spiders were observed in all the treatments. Crematogaster sp and mantids were found in all the treatments except cymethoate. This suggests that the botanicals had little effect on these natural enemies but the synthetic insecticide probably killed them. 5.2.4 Effect of the treatments and pests on growth and yield indices. There were no significant differences in plant height at flowering even though there were 68 University of Ghana http://ugspace.ug.edu.gh slight differences with jatropha seed oil giving the mean highest of 41.8 cm and cymethoate the lowest of 31.7 cm (Table 7). This means that the treatments had no effect on growth of plants in terms of height up to flowering. Highly significant differences (P < 0.01) were observed