ABSTRACT
Field and laboratory experiments were conducted between 2017 – 2020 cropping seasons at Vegetable Farm of National Horticultural Research Institute (NIHORT) Mbato Okigwe Outstation, Imo State, Nigeria to study the efficacy of Tephrosia vogelii aqueous and ethanol extracts in the control of Eggplant Fruit and Shoot Borer (EFSB); Leucinodes Orbonalis Guen infesting eggplants. In experiment one, five varieties of eggplant (Solanum gilo, S. macrocarpon, S. ex-lantan, S. aethiopicum, S. melongena) were screened in the field for their susceptibility to EFSB. The treatments were arranged in Randomized Complete Block Design (RCBD) with four replications. Data on adult moth and larval population, length of feeding tunnel, numbers of holes on fruits and shoots were assessed. In experiment two, laboratory studies were carried out to determine the insecticidal properties of eggplant varieties and Gas Chromatography and Mass Spectrum (GC-MS) analysis was used to identify the bioactive volatile compounds of T. vogelii. In experiment three, field control of EFSB on the most susceptible eggplant variety (S. gilo) using T. vogelii extracts (10%w/v, 20%w/v, 30%w/v, 9%v/v, 18%v/v and 27%v/v) and frequency of application [Once a week (1W), once in two weeks (2W) and Once in three weeks (3W)]was conducted. The experiment was laid out in 8 × 3 factorial fitted into RCBD with three replications. Data on population of adult moth, number of holes on shoots and fruits, fruit yield, percent reductions in yield damage, yield increase and yield damage were assessed. Data collected were subjected to Analysis of Variance (ANOVA) using GenStat Software Programme (2010). Significant means were compared with Least Significance Difference (LSD) at P ≤ 0.05. Results showed that population of L. orbonalis adult moth infestation peaked (16.15) in September. S. gilo was the most susceptible eggplant variety with 32.10 % larval infestation. Phytochemical analysis revealed that S. gilo had lowest concentrations of flavonoids, alkaloids, saponins, glycoside, tannin except steroid which was found in high concentrations. The GC-MS analysis of T. vogelii identified 58 bioactive volatile compounds with Benzene, 1,3-bis (2,2-dimethylpropyl), 2,4,5,6-tetramethyl- (19.78 %), Benzo(c)carbazole (6.98%), 7-Oxabicyclo (4.1.0) heptane, 3-Oxiranyl- (6.1 %) as some of predominant compounds. Once a week (1wk) application of treatments have significant effect (P≤0.05) on percent reduction in numbers of holes, damage fruits and uninfested shoots in the first and second cropping seasons. Highest yield (1.6t/ha) was obtained in plots treated to 1W application.
TABLE OF
CONTENTS
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgments v
Table of Contents vi
List of Tables x
List of Figures xii
List of Plates xiv
Abstract xv
CHAPTER
1: INTRODUCTION
1.1 Background
of Study 1
1.2 Objectives of the Study 4
1.2.1 Specific objectives for experiment 1 4
1.2.2 Specific objectives for experiment 2 4
1.2.3 Specific objectives for experiment 3 5
CHAPTER 2:
LITERATURE REVIEW
2.1 Origin and Distribution of Eggplant 6
2.2 Botany of Eggplant 7
2.3 Agronomy of the Eggplant 7
2.4 Importance and Uses of Eggplant 9
2.5 Proximate and Phytochemical Composition of
Eggplant 11
2.6 Climatic Requirements of Eggplant 12
2.7 Soil Requirements of Eggplant 13
2.8 Fertilizer Requirements of Eggplant 13
2.9 Yield of Eggplant 14
2.10 Insect Pests of Eggplant 14
2.11 Insect Pest Management in Eggplant 18
2.12 Biology/Lifecycle
of EFSB L. orbonalis 20
2.12.1 Origin
of EFSB 21
2.12.2 Host
plants/species affected by eggplant fruit borer 21
2.12.3 Symptoms
of damages 23
2.12.4 General
prevention/control strategies for eggplant fruit and shoot bearer
(EFSB) 25
2.12.5 Cultural
control of EFSB 28
2.12.6 Host
plant resistance 29
2.12.7 Biological
control of EFSB 31
2.1.2.8 Chemical
control of EFSB 32
2.12.9 Mechanical
control of EFSB 33
2.12.10 Integrated pest management
(IPM) tactics and control measures for EFSB
(Leucinodes orbonalis) 34
2.12.11 Natural control agents of
eggplant shoot and fruit bearer 35
2.12.12 Losses due to EFSB impact on
eggplant 36
2.13 Plant Derived Insecticide (Bio-Insecticide)
Used for the Current Trial 37
2. 17 Nature
of Tephrosia vogelii Hook F. 38
CHAPTER
3: MATERIALS AND METHODS
3.1 Experiment One: Assessment of
Susceptibility/Resistance Level of Five
Solanum
Varieties to Leucinodes orbonalis Infestation 40
3.1.1 Location
and site characteristics 40
3.1.2
Planting materials 40
3.1.3
Nursery practices 41
3.1.4 Land preparation, soil sampling and plots
delineation 41
3.1.5
Transplanting of seedlings 41
3.1.6 Experimental design 41
3.1.7 Data collection 42
3.1.8 Data analysis 43
3.2 Experiment Two: Field Control of Eggplant
Shoot and Fruit Borer,
Leucinodes
orbonalis Guen. (Lepidoptera: Pyralidae) Using Tephrosia
vogelii Extracts and Time of Application on
Eggplant, Solanum gilo 45
3.2.1 Botanicals 45
3.2.2 Cypermethrin and ethanol 45
3.2.3 Preparation and application of plant extract 45
3.2.4 Experimental treatments 46
3.2.5 Experimental design and layout 47
3.2.6 Data collection 47
3.2.7 Data analysis 48
3.3 Experiment Three: Phytochemical Screening
of Five Varieties
of Eggplant, Solanum Spp. Fruits for Insecticidal Properties 48
3.2.1
Collection,
identification of specimens and preparation 48
3.2.2
Phytochemical analysis 48
3.2.3 Gas
chromatography-mass spectrometry (GC-MS) analysis of Tephrosia
vogelii 49
CHAPTER
4: REULTS AND DISCUSSION
4.1 Field
Screening of Five Varieties of Eggplant for EFSB Susceptibility 52
4.2 Field Control of Eggplant Shoot and Fruit
Borer (EFSB), L.
orbonalis Guen. (Lepidoptera: Pyralidae) on Solanum gilo Using Aqueous
and Ethanol Extracts of T. vogelii and Frequency of Application
in two
Planting Seasons 61
4.2.1 Percentage fruit and shoot infestations,
number of EFSB adult
moth and larva as Influenced
by treatments and Frequency of
application on S. gilo in the first planting season 61
4.2.2 Effects of application frequency on the
infestation of EFSB, the level
of damage caused by EFSB and
resultant yield performance of S. gilo
in
the two planting seasons 75
4.2.3 Interaction effect of treatments and
application frequency on the
measured parameters in the
first and second planting seasons 86
4.3 Phytochemical
screening of the fruits of the eggplant varieties 112
4.3.1 Bioactive Volatile Compounds of Tephrosia vogelii 113
4.4 Discussions 119
4.4.1 Assessment of susceptibility/resistance
level of five solanum
varieties to Leucinodes orbonalis infestation 119
4.4.2 Field control of eggplant shoot and fruit
borer (EFSB),
Leucinodes orbonalis Guen. (Lepidoptera: pyralidae) using T. vogelii
extracts and time of
application on eggplant, Solanum gilo 121
4.4.3 Phytochemical screening of the fruits of the
eggplant varieties 123
CHAPTER
5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 129
5.2 Recommendations 130
References 160
Appendix 190
LIST
OF TABLES
2.1: Some Important
Insect Pests of Eggplant 15
2.2: Some Bioactive
Compounds Found in Tephrosia vogelii 39
4.1.1: Monthly Abundance of L. orbonalis Adult Moth on Eggplant Varieties 55
4.1.2: L. orbonalis Larval Damage of Fruits and
Shoots of Eggplants 60
4.1.3: Yield Performances of Eggplant Varieties
Exposed to L. orbonalis 60
4.2.1: Level of Damage and Percentage Reduction in Damage due to EFSB
Infestation
and Application of Treatments on S. gilo
in the two
Planting
Seasons respectively 70
4.2.2: Effects of Application Frequency on the Level
of Damage Caused by
EFSB on S. gilo in the two
planting seasons 83
4.2.3.1:
Interaction Effect of Treatments and Application Frequency on
Percentage Fruits Infestation 87
4.2.3.2:
Interaction Effect of Treatments and Application frequency on Percentage
reduction in the Number of Holes Per
Fruit 89
4.23.3: Interaction Effect of Plant extracts and
Application Frequency on
Percentage Reduction in the Number
of Holes Per Shoot 92
4.2.3.4 Interaction Effect of Treatments and
Application Frequency on
Percentage Reduction in Fruit Damage 93
4.2.3.5:
Interaction Effects of Plant Extracts and Application Frequency on
Percent Shoot Infestation of S. gilo in the First and Second Planting
Seasons 95
4.2.3.6:
Interaction Effect of Plant Extracts and Application Frequency on
Number of Holes per Fruit Per Plant 97
4.2.3.7:
Interaction Effect of Treatments and Application Frequency on Number
of Adult Moths 99
4.2.3.8:
Interaction Effect of Treatments and Application Frequency on number
of Damaged Fruits Per Plant 101
4.2.3.9:
Interaction Effect of Treatments and Application Frequency on Number
of Holes Per Shoot Per Plant 103
4.2.3.10:
Interaction Effect of Treatments and Application Frequency on Number
of larvae 105
4.2.3.11:
Interaction Effect of Treatments and Application Frequency on Number
of Wholesome Fruits Per Plant 107
4.2.3.12:
Interaction Effect of Treatments and Application Frequency on Number
of Infested Shoots 109
4.2.3.13:
Interaction Effect of Treatments and Application Frequency on
Number
of Uninfested Shoots 111
4.3.1: Phyto-chemical
Screening Results of the Fruits of the Eggplant Varieties 114
4.3.2: Detected
Bioactive Compounds of T. vogelii
from GC-MS Analysis 115
LIST
OF FIGURES
1.1: Geographical Distribution of Leucinodes orbonalis 22
4.1.1: Population Dynamics of EFSB
Infesting Different Varieties of
Eggplant 56
4.1.2: Percentage L. orbornalis Larval Infestation Per Month 56
4.1.3: Percentage EFSB larval
Infestation on Eggplant Varieties 57
4.1.4: Number of L. orbornalis Occurrence per Eggplant Variety 57
4.2.1: Treatment
Effects on Percent Infestation and Number of EFSB
Adult Moth and Larva in S.
gilo Cultivated in 2017/2018
Cropping Season 62
4.2.2: Treatment Effects on Percent
Infestation and Number of EFSB
Adult Moth and Larva in
2019/2020 Cropping Season 64
4.2.3:
Yield (tha-1) of S. gilo as Influenced by T. vogelii Aqueous
and Ethanol Extracts in
First Planting Season (2017/2018
Cropping Season) 72
4.2.4: Number of Wholesome Fruits per
Plant as Influenced by T. vogelii
Aqueous and Ethanol
Extracts in First Planting Season
(2017/2018 Cropping
Season) 72
4.2.5: Yield (tha-1) of S. gilo as Influenced by L. orbornalis Infestation
under T. vogelii Extracts Application in the
Second Season
(2019/2020 Cropping Season) 74
4.2.6: Number
of Wholesome Fruits Per Plant Per Plot as Influenced by
EFSB Infestation in the Second Planting Season
(2019/2020
Cropping Season) 74
4.2.7: Effects
of Application Frequency of Treatments on Percent
Infestation
in the First Planting Season (2017/2018 Cropping
season) 76
4.2.8 Effects
of Application Frequency on Percent Infestation in the
Second
Planting Season (2019/2020 Cropping Season) 78
4.2.9: Effect
of Application Frequency on the Yield of S.
gilo in First
Planting
Season (2017/2018 Cropping Season) 79
4.2.11: Effect
of Application Frequency on Yield (tha-1) Per Plant in the
Second
Season (2019/2020 cropping season) 85
4.2.12: Effect
of Application Frequency on Number of Wholesome
Fruits
per Plant in the Second season (2019/2020 cropping season) 85
4.3.1: Chromatogram
of Volatile Compound of T. vogelli leaf 117
4.3.2: Spectral
Structure of 7-Oxabicyclo (4.1.0) Heptane, 3-oxiranyl
Compound
obtained from T. vogelii Leaf 118
4.3.3: Spectral
Structure of Benzo(c) carbazole Compound Obtained from
T.
vogelii Leaf 118
LIST
OF PLATES
1: Life Cycle of L. orbonalis 20
2: Shoot Boring by Leucinodes orbonalis 24
3: Fruit Infested by L. orbonalis Internal Feeding 24
4: Growing Point - Internal Feeding;
Boring by EFSB 24
5: Solanum Varieties at the Nursery Stage 44
6: Land
Preparation/Preparation 44
7: Newly
Transplanted Seedlings 44
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF STUDY
Eggplant
is a popular vegetable crop grown all over the world, including West Africa. It
belongs to the Solanaceae family and is among the top five essential indigenous
vegetable crops cultivated globally alongside onions, peppers, tomatoes, and
okra (Messiaen, 1992). This tropical and sub-tropical woody herb can grow up to
1.5 m tall and typically has long taproots and branches (Anna, 1991).
Eggplant
is highly adaptable and can withstand both drought and excessive rainfall,
making it a resilient crop (Messiaen, 1992). According to recent data, the
worldwide eggplant production in 2021 was approximately 55,197,878 metric tons,
with Nigeria importing 158 metric tons valued at USD 150 (FAO, 2021).
Furthermore, in Nigeria, various local varieties of eggplant exist and are
grown by different ethnic groups for local consumption and other purposes.
The
fruit of eggplant can be eaten raw as a vegetable or boiled, fried, and stuffed
before consumption (Rice et al., 1987). The leaves of some varieties can
also be eaten raw or boiled, providing all the essential amino acids, vitamins,
and minerals in adequate quantities (Taylor, 1983). Eggplant
is important in the sub-Saharan Africa region for food security, medicinal and
traditional usages. The fruits could be eaten raw, processed to make soup and
food additives. Eggplants are widely used in traditional medicine (Mwai et
al., 2007). The world production of Eggplant in 2001 was 23 million tons
from 1.4 million hectares with Africa producing less than 4 % of the world
production and area (Bukenya and Bonsu, 2004). Additionally, the
alkaloid solanine extracted from the roots and fruits of eggplant is used for
therapeutic purposes (Yayock et al., 1988).
Recent
studies have shown that eggplant contains significant amounts of antioxidants,
such as phenolic compounds and anthocyanins, which have various health
benefits, including reducing the risk of chronic diseases (Patil et al.,
2021). Additionally, eggplant has been found to have antidiabetic,
anti-inflammatory, and anticancer properties (Patil et al., 2021;
Mahajan et al., 2021).
Eggplant
is a versatile and resilient vegetable crop with significant nutritional and
medicinal benefits. Its popularity continues to grow, and it remains an
essential part of the global food system, particularly in West Africa.
African eggplants, also known as garden eggs, are highly valued in
Nigerian cuisine and traditional medicine. These plants are a staple food for
both rural and urban families, and are consumed almost daily (Tindal, 2005).
The crop's popularity is due to its prolific fruit production, large fruit
size, and quick maturation time. In southeastern Nigeria, eggplants are
commonly served during traditional and religious ceremonies, such as weddings,
funerals, and child dedications (PROTA, 2004; Bukenya and Bonsu, 2004). The
immature fruits can be eaten raw or cooked.
Eggplants are known for their ability to produce a bushy, vigorous
plant with large leaves, stems, and attractive flowers. These plants have a
deep taproot that enables them to tolerate dry weather. The flowers of
eggplants are open for two to three days and are self-pollinated (Lewis, 2005).
The fruit of the eggplant comes in various sizes and shapes, ranging from round
to bell-shaped, oval, or elongated. The fruit surface is smooth and glossy, which
can be yellow, green, white, purple, black, violet, or various combinations of
these colors (AVRDC, 1996; Lewis, 2005).
The
production of eggplant is often limited by pests and diseases, particularly
during the dry season when the crop commands higher prices. These biotic
factors can be harmful to the plants, leading to reduced yield and economic
value of the crop. The major pests affecting eggplant include Eggplant Fruit
and Shoot Borer (Leucinodes orbonalis), Empoasca spp.,
cutworms (Agrotis segetum), Zonocerus variegatus,
and leaf miners (Diglyphus sibirica) (Schippers, 2000), causing yield
losses of between 75 – 90 % of the crop (Onekutu, 2011).
The
use of synthetic insecticides such as Cypermethrin and Deltamethrin has been
explored as a way of controlling the pests. However, the hazardous effects of
these pesticides have become a major source of concern to environmentalists. As
a result, alternative options for managing insect pests have become imperative.
The use of botanicals is more acceptable to farmers because of their general
safety and ease of handling (Emeasor et al., 2005).
Several
botanicals have been found to have insecticidal properties that can effectively
control pests on eggplant. For instance, extracts from neem (Azadirachta
indica), ginger (Zingiber officinale), garlic (Allium
sativum), and tobacco (Nicotiana tabacum) have been shown
to be effective against the Eggplant Shoot and Fruit borer (Leucinodes orbonalis)
(Rahman et al., 2014). Additionally, some microbial biocontrol agents
such as Beauveria bassiana and Metarhizium anisopliae
have also been found to be effective against eggplant pests (Kashyap et al.,
2014).
Overall,
the use of botanicals and microbial biocontrol agents offers a more
environmentally friendly and sustainable approach to managing insect pests in
eggplant production.
Tephrosia vogelii hook F. is
a small leguminous shrub, traditionally used for its ichthyotoxic,
insecticidal, and food parasiticidal properties (Adams,1998). T. vogelii
is a potential source of rotenone, a non-residual insecticide, and tephrosin. It
helps in soil fertility restoration and is used for poisoning fish. The plant
has low toxicity compared to other species used in the industry. Several
isoflavonoids with different effects have been isolated from Tephrosia
species. Small-scale farmers in Kenya use the roots and leaves of T. vogelii
to control pests and diseases. The plant has also shown biological activity
against field and stored product insects (Ibrahim et al., 2000).
1.2 GENERAL
OBJECTIVE OF THE STUDY
This study aimed to assess the effectiveness of Tephrosia
vogelii in controlling Leucinodes
orbonalis, EFSB.
1.2.1 Specific
objectives for experiment 1:
(Assessment of susceptibility of five Solanum
varieties to Leucinodes orbonalis infestation)
l To determine the time of
infestation of five Solanum varieties
by L. orbonalis
l To determine the nature
and level of damage caused by L.
orbonalis infestation to different Solanum
varieties
l To compare the yield of
five Solanum varieties under L. orbonalis infestation
1.2.2 Specific objectives for experiment 2:
(Field
control of EFSB, Leucinodes orbonalis Guenee [Lepidoptera: Pyralidae] using
Tephrosia vogelii extracts and time of application on eggplant, Solanum
gilo)
l To evaluate the efficacy of aqueous and ethanolic extracts of T. vogelii for the control of EFSB, L. orbonalis
l To compare the effectiveness of the application of aqueous and
ethanolic extracts of T. vogelii for
the control of EFSB, L. orbonalis
l To determine the most effective rate of application of aqueous and
ethanolic extracts of T vogelii for
the control of EFSB, L. orbonalis
l To determine the frequency of application of aqueous and ethanolic
extracts of T. vogelii that will be
most effective in the control of EFSB.
1.2.3 Specific
objectives for experiment 3:
(Phytochemical screening of five varieties of eggplant
fruits and analysis of T. vogelii using Gas Chromatography - Mass Spectrometry
(GC-MS)
l To determine and assess
the quantitative and qualitative components of the phytochemicals in the five
varieties of eggplant (S. gilo, S.
aethiopicum, S. melongena, S. ex-lantan and S. macrocarpon).
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