INSECT FAUNA ASSOCIATED WITH WATERMELON FARMS IN DELTA STATE, NIGERIA

Abstract

A survey of the insect fauna associated with watermelon farms in Abraka, Delta State, Nigeria was carried out during the early planting season. This was aimed at determining the composition of insects found around watermelon farms and the period which the plants are most susceptible to the insect pest infestation. This study was carried out between March and May, 2018 covering the planting and harvesting period of the plant. The insects were collected by hand picking, beating trays and insect nets trapping. A total of 1081 individuals represented by 12 species of 4 families were recorded. Most of the insects found were known to be harmful species but two species (X. virginica and A. cerana) were known to be beneficial species. Aulacophora lewissi was considered to be the dominant insect pest of the watermelon plants in the area. It accounted for had the highest number of pest infesting the plant (238) while A. analis was least. The study revealed that infestation started on the 2 nd week after planting but the highest period of insect infestation was observed on the 5 th week when flowers began to emerge and there was significant difference (p<0.05) in the number of insects as infestation occurred through the weeks. Most of the insects infesting the watermelon plants were Coleoptera (beetles). The beneficial insects were majorly pollinators (bees), especially Xylocopa virginica that emerged at the 5 th week when the plants were flowering. Information on the stage (s) at which the plant is most vulnerable to the pest infestation is considered crucial in Insect Pest Management. In line with this, findings in this study suggested that Control and Management Practices would be most effective from the second week of planting.

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Nigerian Journal of Science and Environment. Vol. 17 (1) (2019)
57
INSECT FAUNA ASSOCIATED WITH WATERMELON FARMS IN DELTA
STATE, NIGERIA.
OJIANWUNA, C. C.
Department of Animal and Environmental Biology,
Delta State University, Abraka.
Abstract
A survey of the insect fauna associated with watermelon farms in Abraka, Delta State, Nigeria was
carried out during the early planting season. This was aimed at determining the composition of insects
found around watermelon farms and the period which the plants are most susceptible to the insect pest
infestation. This study was carried out between March and May, 2018 covering the planting and
harvesting period of the plant. The insects were collected by hand picking, beating trays and insect
nets trapping. A total of 1081 individuals represented by 12 species of 4 families were recorded. Most
of the insects found were known to be harmful species but two species (X. virginica and A. cerana)
were known to be beneficial species. Aulacophora lewissi was considered to be the dominant insect
pest of the watermelon plants in the area. It accounted for had the highest number of pest infesting the
plant (238) while A. analis was least. The study revealed that infestation started on the 2nd week after
planting but the highest period of insect infestation was observed on the 5th week when flowers began
to emerge and there was significant difference (p<0.05) in the number of insects as infestation
occurred through the weeks. Most of the insects infesting the watermelon plants were Coleoptera
(beetles). The beneficial insects were majorly pollinators (bees), especially Xylocopa virginica that
emerged at the 5th week when the plants were flowering. Information on the stage (s) at which the
plant is most vulnerable to the pest infestation is considered crucial in Insect Pest Management. In line
with this, findings in this study suggested that Control and Management Practices would be most
effective from the second week of planting.
Keywords: Watermelon, Insect, species, harmful, beneficial.
Introduction
Watermelon (Citrullus lanatus Thumb)
belongs to the family Cucurbitaceae.
Citrullus colocynthis is known to be a wild
ancestor of watermelon (Dane and Liu,
2007). Watermelon originated in South
Africa from the Kalahari desert with
evidence of its cultivation in ancient Egypt
but it can now be found in both tropical and
subtropical climates worldwide (Schippers,
2000). Watermelon has been known to be an
indigenous plant to Nigeria and some other
parts of the Tropical Africa since the 19th
century (Huh et al., 2008). Although, this
plant is cultivated in several regions in the
country, the Northern part of the country has
been identified as the main producers of the
crop (Oladele, 2015). The potentials of
watermelon as cash generating crop is
significant for farmers especially those
residing near the urban areas. Oguntola
(2006) observed that watermelon is the most
preferred among five other exotic
vegetables examined in Ibadan Metropolis
of Oyo State, Nigeria. Watermelon
production generally generate higher profit,
provides more employment and income to
the farmers than other indigenous
vegetables. Watermelon is a warm seasonal
crop that thrives very well in most well
drained soils (clay or sandy) but preferably
sandy loams (Bertelsen et al. 1994).
Watermelon can be cultivated successfully
twice a year and there are two main planting
periods-the early planting period and late
planting period. The early planting period
begins in late February to first week of
March, while the late planting period begins
in late August to early September. It takes
about 80 100 daysfor watermelon seed to
reach maturity (Spreen et al. 1995).
Watermelon is very beneficial to man
because of its nutritional, therapeutic and
income earning value (Okrikata and
Oludele, 2015).

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58
Insect pest infestations had been the
most important constraint of watermelon
farming in Nigeria. This had caused reduced
quality and yield of the crops in recent years
(Ngbede et al 2014). Some of the insect
pests that have been recorded infesting
watermelon are; Phyllotre cruciferae,
Zonocerous variegatus, Aulacophora
africana and Dacus cucurbitae. In Nigeria,
insect past infestation has been reported in
some watermelon growing states. For
instance, in Benue State, arthropod caused
about 91.1% damage to watermelon while
Nasarawa and Taraba state recorded 88.9%
and 87.2% respectively. Beetles have been
identified as the most abundant and
damaging arthropod accounting for a rating
of 88.9% in Benue State while 86.7% and
61.5 % infestations were recorded in
Nasarawa and Taraba State respectively.
The second most abundant damaging
Arthropod in Taraba State was the Sting bug
which accounted for a rating of 23.1%.
Although, these bugs were absent in
Nasarawa and Taraba State (Okrikata and
Oludele, 2015). Furthermore, the
distribution and population density of these
insect pests are known to be influenced by
agro climatic conditions. These conditions
enable the beneficial insects such as bees to
thrive very well and this may help in
pollination of the flowers. As such,
information on the insect pest fauna
infesting water melon plants is crucial.
Hence, this study which seeks to provide
information on the composition of insect
pest infesting water melon plants in Delta
state. This is aimed at providing
information on the stage at which the plant
is most vulnerable to the insect pest
infestation and when the management and
control measures could be most effective.
Materials and Methods
Land preparation and Planting
The experimental study was carried
out at the Abraka Government Reserve
forest of Delta State, Nigeria during the
early planting season from March to May,
2018. An acre of land divided into four plots
was used for planting. Herbicides (Uproot
and Force up) were sprayed on the grasses
to kill them and two weeks after, they were
burnt. The Planting of the seeds
commenced three days after burning.
Improved variety of canned watermelon
seeds (Kaolack from France) were used for
planting. Two seeds were dropped per hole
with the holes having a distance of 1m by
2m apart on the plot. This method was
adopted from Alao et al. (2016) (With slight
modifications) Weeding of the farm land
took place every three weeks.
Monitoring the Plants for Insect Pests
Insect activities were closely monitored
immediately after planting.This was done
every week. However, serious attention was
paid on the composition and abundance of
these insects at each stage of plant growth.
Records of abundance and infestation by
insects were taken on weekly basis.
Collection of insects was carried out
between 8am-1pm each sampling day by
hand picking, beating methods and insect
net trapping methods. Insects were counted
visually from each watermelon plant in the
plot of land. After collection, they were
placed carefully inkilling jarsand taken to
the Laboratory for identification. The
collection of insects were done from
germination of the seeds when they began to
appear till maturity (from week 2 to week
12).
Data Analysis
Data was subjected to descriptive statistics
using the SPSS software.
Results
Observations in the study showed that on
the third day, the water melon seeds
germinated and there was no immediate
insect infestation on the plants throughout
the first week of planting. Insect activities
began at the second week and increased
rapidly as the week progressed. Flowers
started emerging from the 5th week and the
plants began to fruit at the 6th week. The
distribution of insects within the weeks is
presented in the Table 1. It was observed

Nigerian Journal of Science and Environment. Vol. 17 (1) (2019)
59
that there was significant difference
(p=0.02) in the number of insects that
visited the plants as the weeks progressed
from 2nd week to the 12th week. There was
also significant difference (p<0.05) between
the species of insects found in the farm.
The table also shows that most of the insect
order infesting watermelon farm in this
study were Coleoptera (beetles) (Figure 1)
and species-Aulacophora lewissi was
highest in number (238) infesting the
watermelon farm while Aulocophora analis
was the least number (7) .The highest
period of insect infestation wasobserved in
the 5th week while the lowest period of
infestation was in the 2nd week. Z
variegatus was also an important insect pest
infesting the plants from the 2nd week to the
12th week. Cheilomenes sp occurred from
the 9th week attacking fruits and plant
parts.The table also shows that some insects
such as Apis cerana and Xylocopa virginica
(Bees) appeared at the 5th week (when they
began to flower) to the 12th week.

Nigerian Journal of Science and Environment. Vol. 17 (1) (2019)
61

Figure 1-Insect Order Associated with Watermelon Farm in Delta State, Nigeria
Discussion and Conclusion
the most limiting factor of watermelon
production in Nigeria and other developing
countries (Ngbede et al 2014). Most
infestations in this study started at the 2nd to
the 5th week and some lasted till the end of
the 12th week. This finding is in line with
Alao et al. (2016) in which insect infestation
commenced at the 2nd week after planting
when the young leaves appeared. It was
observed that A. lewissi and A. foveicollis
fed on all parts of plant seedlings
throughout the plant cycle but infestation
was most abundant from the 2nd to the 5th
week. Even as the flowers began to emerge
at the 5th week, the insects were found to
feed on the younger seedlings, the flowers
and young fruits of the plants though in
lower numbers. The immature stages of the
insects were also observed to have fed on
these plant parts. A. nigripennis was
observed to have fed on the plants at the
young seedling stage too but they never
appeared as the plants began to flower and
fruit. The Aulacophora species were
perceived to have preference for young
plants with tender leaves but as the plants
matured and leaf canopy increased, their
defoliating preference reduced. This
observation is similar to the findings in
Yamaguchi (1984) which reported that
insects from the genus Aulacophora (A.
oveicollis) caused 35-75% damage to all
cucurbits at seedling stage. The rate of
infestation started decreasing as flower
started emerging till the plants reached
fruiting stage.
Zonocerus variegatus (Grasshopper) was
also recorded as an important pest of
watermelon plants in this study. The adults
and nymphs were observed to have fed on
all insect parts and their population
increased as the fruits started emerging.
Epilachna chrysomelina,Cheilomenes
sulphurea, Cheilomenes propinqua ,
Curinus coeruleus, Aulocophora analis and
Aulacophora indica occurred from the 5th to
12th week. These insects fed on the plants
parts especially the flowers and fruits.
Some species defoliated the flowers and this
caused abortion of fruits and prevented
pollination of the plants. Also, some insects
species may have caused secondary
infection (fungi and bacteria) on the young
76%
11%
13%
Coleoptera(Beetle)
Orthoptera(Grasshopper)
Hymenoptera(Bees)

Nigerian Journal of Science and Environment. Vol. 17 (1) (2019)
62
and matured fruits. Similar observations
have been reported by Alao et al. (2016).
Overall, above 75% of the insects recorded
in this study were beetles and this
observation agrees with the works of
Ogunlana (1996); Bamaiyi et al, (2010);
Okrikata and Oludele (2015) and Alao et
al. (2016) in which beetles were reported as
the most abundant and damaging insect
found on watermelon farms.
Among the species of insects
recorded, A. lewissi was considered the most
destructive insect because it attacked the
economic parts of the crops such as young
seedlings, leaf, stem, fruits and flowers
.This could potentially lead to the
destruction of the plants or the abortion of
the flowers. The larvae stage of this insect
was also observed to have fed on the
flowers and young fruits.
Bees such as Apis cerana (Honey
bee) and Xylocopa virginica (Carpenter
bees) appeared in the 5th week. Their
appearance was considered to be influenced
by the emergence of flowers from the plants
as these insects are known to be pollinating
agents of the water melon plants. Of the
pollinators, Xylocopa virginica was more
abundant than Apis species and their
numbers decreased as the watermelon fruits
began to emerge. Studies have shown that
Apis (Honey bees) are not good pollinators
when compared to other bee species (Aziz
et al., 2010). Apis and Xylocopa were
recorded as the only beneficial insects in
this study. These species have been known
to be important in the pollination of
watermelon plants. Some flowers (male
flowers) produced pollens which were
transferred to the female flowers by these
bees for fertilization to occur. Similar
findings had been reported by Aziz et al.,
(2010); Webb (2013) and Wael et al.
(2017). These studies reported that bees
were very beneficial to watermelon plants as
a result of their pollinating ability.
Conclusion
This study gave an account of the
insect fauna associated with watermelon
farms in Delta State, Nigeria. Most of the
insect pest recorded in this study caused
severe damage to the plants. The damages
done to the leaves, the young seedlings,
flowers and fruits of the plant ultimately led
to the death of the plants at different stages
of the its life cycle. Findings in this study
suggested that Control and Management
Practices would be most effective during the
second week of planting.
Acknowledgement
I acknowledge Omuvwie Rita for
assisting in the collection of the insect
species and Dr. Tunde Amusan for
reviewing the first draft of the manuscript.
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