ABSTRACT
Khapra beetle, Trogoderma granarium Everts, is a serious storage insect pest
of cereals and legumes in the tropical and sub-tropical regions of the world.
The study was carried out in the laboratory at prevailing temperature
(25±50C) and relative humidity (65±5%). Six improved groundnut varieties,
which include SAMNUT 14, SAMNUT 17, SAMNUT 18, SAMNUT 21,
SAMNUT 22 and SAMNUT 23 were examined for their susceptibility to T.
granarium. Susceptibility of these varieties to the dermestid was determined
with respect to kernel damage assessment, mean kernel weight loss and total
larvae population. The food preference of the T. granarium larvae for the
groundnut varieties after six months storage period was also investigated.
SAMNUT 22 variety was the most susceptible while the least susceptible
was SAMNUT 17. Further preliminary laboratory experiments involved
screening of nine indigenous plant powders (leaves/seeds) against T.
granarium larvae. Methanol extracts of five promising plant powders of
Ricinus communis Linnaeus, Hyptis suaveolens Poit., Annona senegalensis Pers.,
Xylopia aethiopica Dunal and Khaya senegalensis Desr. were assayed for their
effects on adult mortality and larval survival of T. granarium. Adult
mortality and survival of larvae of T. granarium were significantly (P<0.05)
different with increased all doses of crude extracts compared with the
control. Adult mortality increased with the concentration of crude extracts
and the duration of exposure of the insects on the treated groundnut kernels.
The crude extracts were almost similar in their effectiveness. However, the
TABLE OF CONTENTS
Title page – – – – – – – i
Declaration – – – – – – – ii
Certification – – – – – – – – iii
Acknowledgements – – – – – – – iv-v
Abstract – – – – – – – – vi-vii
Table of contents – – – – – – – viii-xii
List of Tables – – – – – – – – xii-xiii
List of Figures – – – – – – – xiv
List of Plates – – – – – – – – xv
CHAPTER ONE: INTRODUCTION
1.1 Nomenclature, origin and geographical
distribution of groundnuts – – – – – 1
1.2 Soil and environmental requirements – – – 1
1.3 Production of groundnut – – – – – 2
1.4 Groundnut production constraints – – – – 2
1.5 Uses of groundnut – – – – – – 3
1.6 Justification of the study – – – – – 4
CHAPTER TWO: LITERATURE REVIEW
2.1 Origin and distribution of Khapra beetle – – – 6
2.2 Taxonomy of Khapra beetle – – – – 7
2.3 Insect pests of groundnut – – – – 8
2.3.1 Field pests – – – – – – – 8
9
2.3.2 Pests associated with stored groundnuts – – – 10
2.4 Biology of Khapra beetle – – – 11
2.5 Damage caused by Khapra beetle – – – – 14
2.6 Limitations of synthetic pesticides – – – 16
2.7 Phytochemical control of stored product insect pests – 19
2.8 Plants controlling storage pests – – – – 22
2.8.1 Azadirachta indica – – – – – – 22
2.8.2 Dennettia tripetala – – – – – – 25
2.8.3 Annona spp. – – – – – – – 26
2.8.4 Zanthoxylum zanthoxyloides – – – – – 28
2.8.5 Piper spp – – – – – – – 29
2.8.6 Citrus spp – – – – – – – 29
2.8.7 Eucalyptus spp – – – – – – – 30
2.8.8 Hyptis spp – – – – – – – 31
2.9 Control of Khapra beetle – – – – – 32
2.9.1 Use of synthetic chemicals – – – – – 32
2.9.2 Use of pheromones – – – – – – 33
2.9.3 Non-chemical control – – – – – 34
CHAPTER THREE: MATERIALS AND METHODS
3.1 Insect culture – – – – – – – 36
3.2 Groundnut varieties – – – – – 36
3.3 Moisture content determination – – – – 39
3.4 Collection, identification and preparation of plant samples 39
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3.5 Oil extraction – – – – – – 40
3.6 Varietal susceptibility of groundnut to Khapra beetle
(Trogoderma granarium) larvae – – – – 42
3.7 Effects of plant powders on mortality of T. granarium
larvae on stored groundnuts – – – – 44
3.8 Effects of crude plant extracts on adult mortality and
survival larvae of T. granarium – – – – 45
3.9 Phytochemical screening of plant materials used – 46
3.9.1 Test for tannins – – – – – – 46
3.9.2 Test for alkaloids – – – – – – 46
3.9.3 Test for polyphenols – – – – – 47
3.9.4 Test for flavonoids – – – – – – 47
3.9.5 Test for saponins – – – – – – 47
3.9.6 Test for steroids – – – – – – 48
3.9.7 Test for glycosides – – – – – – 48
3.10 Preparation of samples and examination in an
infrared spectrometer – – – – – 48
3.11 Data analysis – – – – – – – 48
CHAPTER FOUR: RESULTS
4.1 Susceptibility of groundnut varieties to
Trogoderma granarium first instar larvae – – – 50
4.2 Effect of plant powders on mortality of T. granarium larvae – -65
4.3 Effects of crude plant extracts on adult mortality
of T. granarium. – – – – – – 67
4.4 Effects of crude plant extracts on the survival of
T. granarium larvae. – – – – – – 72
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4.5 Combined effects of plant extracts on the survival of
T. granarium- – – – – – – – 80
4.6 Correlation coefficient of time of exposure of
T. granarium larvae to the plant extracts – – – 82
4.7 Active organic chemical ingredients in the test plants – 82
4.8 Spectroscopic analysis of the test plants – – – 84
CHAPTER FIVE: DISCUSSION
5.1 Susceptibility of groundnut varieties to T. granarium larvae – 99
5.2 Mean mortality of T. granarium as influenced by
plant powders – – – – – – – 101
5.3 Mean mortality of T. granarium adults as influenced by crude
plant extracts – – – – – – – 104
5.4 Mean survival of T. granarium larvae as influenced by
crude extracts – – – – – – 106
5.5 Organic components of the test plants – – – 107
CHAPTER SIX: SUMMARY, CONCLUSIONS AND
RECOMMENDATIONS
6.1 Summary of findings – – – – – 109
6.2 Conclusion – – – – – – – 110
6.3 Recommendations – – – – – – 111
References – – – – – – – – 113
Appendices – – – – – – – 136
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CHAPTER ONE
INTRODUCTION
1.1 Nomenclature, origin and geographical distribution of groundnuts
Groundnut, Arachis hypogaea L. (Family Fabaceae) also known as peanut, is
one of the world’s principal oilseed crops, widely grown in areas ranging
from latitude 400N to 400S (Freeman et al., 1999). Groundnut is native to
South America and is grown mainly in the United States of America, West
and East African sub regions as well as India and China (Dung, 1999). It is a
common belief that the peanut originated in Africa, but evidence suggests
that South America – Bolivia – was probably its first home (The Sunday
Tribune–Spectrum–Health Bites of November 3, 2002). From there through
colonization, the use of peanuts spread throughout the world.
1.2 Soil and environmental requirements
Groundnut is drought tolerant and grows in regions of moderate rainfall
(800 mm to 1300 mm/annum) and thrives well in well-drained soils. In the
absence of drought, temperature is the most important single factor that
affects its yield. In addition, the growing season is short, beginning in June
and ending in September. Metcalf and Elkins (1980) showed that for high
yields and superior quality, peanuts require a moderately long growing
period of four to five months with a steady, rather high temperature and a
moderate, uniformly distributed supply of rainfall. Adequate rainfall is
needed especially during the period when the peanuts are forming, followed
by dry conditions.
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1.3 Production of groundnut
Groundnut is widely cultivated on a large scale in several countries of the
world. Important groundnut producing countries are China, India,
Indonesia, Myanmar, Thailand, and Vietnam in Asia, Nigeria, Senegal,
Sudan, Zaire, Chad, Uganda, Cote D’Ivoire, Mali, Burkina Faso, Guinea,
Mozambique, and Cameroon in Africa, Argentina and Brazil in South
America and United States of America and Mexico in North America. India
leads the world in groundnut production and about 40% of the groundnut
entering the world commerce is from India (OEPP/EPPO, 1981). The major
groundnut producing States in Nigeria are Kano, Kaduna, Borno, Bauchi,
Adamawa, Niger and Sokoto (Misari et al., 1980). Estimated annual world
production of groundnut is 18 million metric tons from 18 million hectares
(Egwurube and Dike, 2000). Present annual world production of unshelled
nut is 35.1 million tons from about 25.2 million hectares (FAOSTAT, 2001).
However, Nigeria is the eighth leading producer of groundnut globally with
an average groundnut yield ranging between 500 and 800 kg/ha (Fletcher et
al., 1992).
1.4 Groundnut production constraints
The sustainability of groundnut production in Nigeria is threatened by a
number of factors. The seeds are susceptible to Aspergillus flavus Link ex
Fries invasion and are readily contaminated with aflatoxins (Akano et al.,
2002). Low yields of groundnut are in part due to infection by foliar diseases
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such as early leaf spot (Mycosphaerella arachidis Deighton, stat: conid:
Cercospora arachidicola Hori), late leaf spot (Mycosphaerella berkleyi W. A.
Jenkins, stat: conid: Cercosporidium personatum (Berk. & Curt) Deighton) and
rust Puccinia arachidis Speg) (Allen et al.,1996). The most important constraint
is drought. Rosette epidemic in the mid-1970s decimated the crop as nearly
three quarters of a million hectares of the crop were destroyed and regional
trade worth an estimated US $250 million was wiped out (ICRISAT, 1996).
The groundnut rosette is transmitted by Aphis craccivora Koch (Misari et al.,
1988).
1.5 Uses of groundnut
Groundnut is the most important food legume in Nigeria (Ezeaku and
Shehu, 2003). The crop not only sustains soil fertility but is also an important
source of income for small-scale farmers. It is a major source of oil for
humans and the cake, after oil extraction, is a major source of protein for
livestock. Groundnuts constitute an important cash crop and is only
surpassed by cotton and tobacco.
Groundnut is one of the most nourishing foods available in the world. The
U.S. Department of Agriculture reported that it has five important nutrients,
which include food energy, protein, phosphorus, thiamine and niacin
(OEPP/EPPO,1981). Apart from their nutritional value, groundnuts have
considerable medicinal value.
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1.6 Justification of the study
The economic damage caused by Trogoderma granarium Everts on grains
especially oil seeds is not known in Nigeria. This might be attributed to the
behaviour of the insect pest and the dearth of information available on the
pest. The behaviour of the insect pest has raised the awareness to apply
synthetic fumigants such as methyl bromide and phosphine when farmers
are threatened by the insect. This perception has led to consequent
repercussions on the farmers and environment including cost and
environmental hazards or even depletion of the ozone layer. The current
search for alternative control measures against T. granarium therefore
becomes necessary and imperative.
To date, there is little research report or anectodal information on the
effectiveness of plant product components on the activities of T. granarium in
groundnuts. During storage, T. granarium on sorghum (Jood et al., 1996a),
maize (Jood et al., 1993a), and on wheat (El Nadi et al., 2001) have been
controlled with plant products. Larvae of T. granarium in large numbers,
cause considerable damage to stored groundnut compared to non-feeding
adults, which are less in number with short life span. This research was
undertaken to examine the efficacy of well-proven biopesticides on T.
granarium to replace the imported, more expensive and hazardous fumigants
being used to control the storage pest.
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The objectives of the study were to:
1. compare the susceptibility of groundnut varieties to Khapra
beetle, T. granarium larvae
2. assess the efficacy of plant powders on the mortality of larvae
of T. granarium on stored groundnuts.
3. assess the effects of methanol extracts of some of the promising
plant powders (in 2 above) on adult mortality and emergence
of larvae of T. granarium.
4. qualitatively identify the active ingredients of the most
effective plant extracts, e.g. alkaloids, flavonoids, tannins,
saponins, etc.
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