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American Journal of BioScience
2023; 11(3): 71-81
http://www.sciencepublishinggroup.com/j/ajbio
doi: 10.11648/j.ajbio.20231103.13
ISSN: 2330-0159 (Print); ISSN: 2330-0167 (Online)
Incidence and Populations Fluctuation of Leucinodes
orbonalis Guen. 1854 (Pyralidae) on African Eggplant
(Solanaceae) and Their Relationship with Abiotic Factors
Pierre Stephan Elono Azang
1, *
, Cyril Romeo Heumou
2
, Desiree Chantal Alene
3
, Dounia
1
,
Leslie Carelle Mahanac Njiti
1
, Pierre Ngassam
3
, Joseph Lebel Tamesse
1
, Champlain Djieto-Lordon
3
1
Department of Biological Sciences, Higher Teacher Training College, University of Yaounde I, Yaounde, Cameroon
2
Department of Biology, Higher Teacher Training College, University of Bamenda, Bamenda, Cameroon
3
Department of Animal Biology and Physiology, Faculty of Science, University of Yaounde I, Yaounde, Cameroon
Email address:
*
Corresponding author
To cite this article:
Pierre Stephan Elono Azang, Cyril Romeo Heumou, Desiree Chantal Alene, Dounia, Leslie Carelle Mahanac Njiti, Pierre Ngassam, Joseph
Lebel Tamesse, Champlain Djieto-Lordon. Incidence and Populations Fluctuation of Leucinodes orbonalis Guen. 1854 (Pyralidae) on African
Eggplant (Solanaceae) and Their Relationship with Abiotic Factors. American Journal of BioScience. Vol. 11, No. 3, 2023, pp. 71-81.
doi: 10.11648/j.ajbio.20231103.13
Received: February 18, 2023; Accepted: March 13, 2023; Published: July 6, 2023
Abstract:
The study on the temporal fluctuation of populations and damage caused by Leucinodes orbonalis on African
eggplant (Solanum aethiopicum) fruits was carried out in the forest region of South Cameroon from June 11 to September 22,
2018. It consisted of incubations of the attacked fruits in the laboratory for the study of L. orbonalis abundances and the
evaluation of the damage caused by the same pest directly in the field and during each harvest; followed by the correlations with
abiotic factors. The results showed that out of 331 incubated fruits for 06 harvests and 02 seasons of study, the average number of
adults / fruit of L. orbonalis varied significantly from one harvest to another (F (5, 325) = 27.038, p <0.001) with a peak of 4.37
± 0.66 individuals / fruit (N= 2) at the 2nd harvest (in August), and season to season (F (1, 329) = 15.002, p <0.001) with a peak
of 3.22 ± 0.48 individuals / fruit (N=31) during the short dry season. Damage on S. aethiopicum fruits varied significantly from
one harvest to another (F (5, 325) = 27.038, p <0.001) with a peak of 13.05 ± 4.10% in the first week of harvest in August. This
damage did not change from one season to another (p <0.659). Means weight, length and diameter of an incubated fruit varied
significantly from one harvest to another (F (5, 325) = 5,893; F (5, 325) = 7.71 and F (5, 325) = 7.84; p <0.001 respectively). The
highest means weight, length and diameter were obtained at the 2nd and 3rd harvest with average values of 36.15 ± 6.87g and
40.20 ± 4.40g for the mean weight; 4.03 ± 0.30cm and 3.86 ± 0.15cm for the mean length and 4.15 ± 0.34cm and 4.12 ± 0.20cm
for the mean diameter. Study revealed that the mean number of L. orbonalis per fruit had a significant positive correlation with
mean weight (r=0.39, p <0.01), mean length (r=0.40, p <0.001) and mean diameter (r=0.41, p <0.001) of attacked fruits and
multiple regression equations of y=5.3302x+16.021, R
2
=0.8172; y=0.3103x+2.6544, R
2
=0.8194 and y=0.3684x+2.6037,
R
2
=0.8664 of weight, length and diameter respectively. Field damage showed a positive and non-significant correlation with
precipitation (r = 0.80, p <0.20) and a negative and non-significant correlation with mean temperature (r = -0.737, p <0.262) and
mean relative humidity (r = -0.632, p <0.367). These results are of practical significance in designing appropriate strategies for L.
orbonalis control in eggplant intercropping systems.
Keywords:
Leucinodes orbonalis, Seasonal Variation, Population, Damage, Correlation
1. Introduction
African eggplant (Solanum aethiopicum Linnaeus),
member of the Solanaceous family, is one of the most
important vegetable crops that is widely cultivated across the
African continent especially in West, Central (Southern
Cameroon) and East Africa [1-3]. It is an indigenous species
72 Pierre Stephan Elono Azang et al.: Incidence and Populations Fluctuation of Leucinodes orbonalis Guen. 1854
(Pyralidae) on African Eggplant (Solanaceae) and Their Relationship with Abiotic Factors
that is consumed widely in Cameroon and is a source of cash
for rural households in the southern and central regions on
our country. The results showed that, African eggplant is a
decent source of supplements, minerals, cancer prevention
agents, vitamins, dietary fiber and weight training variables
and proteins [4-6]. One hundred grams of fruit contains
0.7mg iron, 13.0mg sodium, 213.0mg potassium [7], 12.0mg
calcium, 26.0mg phosphorus, 5.0mg ascorbic corrosive and
0.5 International Units of vitamin A and gives 25.0 calories
[8, 4]. The nutritional content of African eggplant is
comparable to that of tomato, but it has a lower content of
vitamin C [9]. Some medicinal properties are attributed to
the roots and fruits and they are described as carminative and
sedative, and used to treat colic and blood pressure [2].
Production of this crop was estimated at 570.00 t for a
cultivated area of 190.00 ha in Ghana in 2004 for a yield of
1.97 t / ha [9]. In 1997, approximately 750 tons of African
eggplant fruits were exported from Ghana and this
constituted about 5% of total production at that time [10].
However, it is currently estimated that the total national
production of garden eggs fruits to be around 30,000 metric
tons [9, 11]. Production constraints faced by farmers are
multiple and low crop yields are compounded in the long-run
by production shocks caused by environmental stresses such
as drought, pests and diseases. A number of pests and
diseases attack this vegetable crop in the field such as mites,
stem borers, fruit borers and flower borers. The damage
caused can reduce yields and affect the quality and quantity
of the produce [9]. Among the many pest species, the
eggplant fruit and shoot borer (ESFB), Leucinodes orbonalis
Guenée (Lepidoptera: Pyralidae) is the most destructive and
cause significant economic damage on Solanum spp. [12, 13].
This fruit and shoot borer is one of the most destructive pest
on S. aethiopicum in Tropical Africa and Southern
Cameroon [13]. It is generally depends on eggplant but
sometimes turns towards other Solanaceous field crops like
potato (Solanum tuberosum), tomato (Lycopersicon
esculentum), pepper (Capsicum annuum) and may be on wild
hosts [14, 4]. The young larvae of this pest attack both fruits
and stems of several species / varieties of Solanum spp. [15].
Eggs are laid on various parts of the plant and after hatching,
larvae develop in the fruit pulp from which they leave at the
pre-nymph stage to pupate in the soil. Egg-laying occurs
during night and incubation period ranges from 3-8 days
depending of environmental conditions [4]. Larvae bore
inside plant shoots and fruits adversely affecting plant
growth, yield and fruit quality, and thus making it unfit for
human consumption [16]. The yield reduction could be as
high as 70% [17, 18, 13]. Yield losses reaching as high as
85-90% have been reported by [19, 20, 21]. Farmers largely
follow the chemical method as it produces quick results.
High-frequency application is the common scenario [21].
However, these chemicals, in many cases, invited the
problems of pesticide resistance, resurgence, secondary pest
outbreak, environmental contamination, residual toxicity and
toxicity to beneficial organisms and disturbance in
homeostasis of natural populations [21, 22]. Because larvae
feed and live inside the fruit, they cannot be effectively
controlled by contact insecticides, while systemic
insecticides are not appropriates for vegetables [13].
Efficient control strategies may associates appropriates use
of pesticides with other control technics [14, 15]. The
integrated pest management (IPM) strategy for the control of
eggplant fruit and shoot borer (EFSB) consists of resistant
cultivars, mass trapping, sex pheromone, cultural practical,
mechanical, biological control methods, physical and
biotechnology control technics and population dynamics
[16]. Implementation of these strategies needs a good
knowledge of incidence and fluctuation population of L.
orbonalis in the southern ecosystem. The general objective
of this work was to study the incidence and monthly
variation of L. orbonalis populations on S. aethiopicum fruits
in relation to seasonality in the forest region of South
Cameroon. Specifically, it consisted of: (i) stand out the
seasonal fluctuation of emerged populations of L. orbonalis
on incubated fruits, (ii) evaluate damage on fruits of S.
aethiopicum due to L. orbonalis (iii) stand out the correlation
between mean number of adults of L. orbonalis emerged
from the incubated fruits and the weight and size (length and
diameter) of the fruits, finally (iv) to stand out the correlation
between the field attack rates due to L. orbonalis and abiotic
factors.
2. Materials and Methods
2.1. Study Site and Period
Our study was carried out in the campus of the Higher
Teacher Training College of the University of Yaoundé I,
forest zone of South Cameroon, precisely in the urban area of
Yaounde, Central Region. This study site has the following
geographical coordinates: Lat. 03° 51’35.5”N; Long. 011°
30’37.1’’E; asl. 729m (Figure 1). In the city of Yaounde,
which has a population of around 2 million, there is a
population density that varies from one locality to another
from 14 to 88 inhabitants per square kilometer. The existing
habitat is diverse and the degree of urbanization varies from
one neighborhood to another [24]. The city of Yaounde is
dominated by an equatorial climate of transition to four
seasons. The long dry season extending from mid-November
to mid-March, the short rainy season from mid-March to the
end of June, the short dry season from July to August and the
long rainy season from September to mid-November [25]. The
study period extended from June to September 2018
(corresponding to the harvest period). The fruit harvest period
(which was limited to the fruiting phase) covered two seasons:
the short dry season and the long rainy season.
American Journal of BioScience 2023; 11(3): 71-81 73
Figure 1. Study site (Higher Teacher Training College Campus of the University of Yaoundé I, Centre Cameroon).
2.2. Soil, Geology and Vegetation
Soils derived from the city of Yaoundé are ferralitic on
interfluves [26]. The superficial levels of these soils are not
only a support but also a reserve of nutrients and water for the
plants. The region of Yaounde has a relief characterized by
alternating hills and swampy lowlands [24]. The lithological
substratum of this city consists of metamorphic rocks of
gneissic nature. The vegetation of the city of Yaounde initially
included in the so-called semi-deciduous forest estate is
strongly degraded because of urbanization [27]. At the
phytophysionomic level, the landscape of this city is
dominated by deciduous forest [28]. This forest is degraded in
places due to human activities. In the Higher Teacher Training
College campus, the original vegetation was destroyed in
favor of the construction of classrooms. The site that was
exploited for our study is a plot that has never been used for a
crop. The dominant vegetation in this setting was Sissongo
(Pennisetum purpureum) and Mimosa pudica. Tree vegetation
does not exist here.
2.3. Weather Data
Rainfall and temperature data for the year 2018 as part of
our study were provided by Weatherbase.com. According to
these data, the city of Yaoundé received 1546.9 mm of total
rainfall and had an average annual temperature of 23.3°C.
January was the hottest month with an average temperature
of 24.4°C and August, the coolest month with an average
temperature of 22.2°C. In the city of Yaoundé, most of the
rain fell in October with 299.7mm of rainfall and the least
rain fell in December with an average of 20.3mm of
precipitations.
2.4. Biological Material
In this work, the biological material consisted of the plants
of a single variety of Solanum aethiopicum: the local zong
variety, whose seeds were extracted from fruits from the
Mokolo market at Yaounde, Central Region of Cameroon.
Eggplant before flowering and fruiting phase in the
experimental field are shown in Figure 2.
Figure 2. (a): Plant of S. aethiopicum (eggplant var. Jakatu), (b): Mature
young fruits during fruiting phase.
2.5. Experimental Design
The experimental space, left fallow for two years, was
weeded, cleaned and plowed two weeks before transplanting.
On this parcel, four (04) ridges of local variety of eggplants
were prepared. Les quatre billons servant à l’étude
s’étendaient sur une superficie de 30 m
2
. Each ridge was 4 m
long by 1.5 m wide with 10 young plants transplanted on two
lines, including five plants per line, with a spacing of 0.8 m
between plants of the same line and 1 m between plants of
two different lines. The spacing between two ridges was 0.5
m. We obtained a total of 40 plants to sample.
74 Pierre Stephan Elono Azang et al.: Incidence and Populations Fluctuation of Leucinodes orbonalis Guen. 1854
(Pyralidae) on African Eggplant (Solanaceae) and Their Relationship with Abiotic Factors
2.6. Data Collection
2.6.1. Seasonal Fluctuation of Emerged Populations of
Leucinodes orbonalis
The harvested fruits and attacked in the field were
incubated in transparent boxes of 15cm x 8cm x 4cm in the
laboratory of Zoology of the Higher Teacher Training College
of the University of Yaoundé I. These incubated fruits
contained young larvae of Leucinodes orbonalis. Each box
containing a single attacked fruit and was covered with a fine
mesh fabric to prevent escape of emerging adults. Emerging
adults of L. orbonalis were counted by incubated fruit, by
harvest and by season in order to highlight the seasonal
fluctuation of their populations.
2.6.2. Evaluation of Attack Rates Due to Leucinodes
orbonalis from Fruits Harvests, Counts with Larval
Exit Holes
To evaluate attack rates due to L. orbonalis, we have
regularly harvested fruit during the period from fruit ripening
to the end of the fruiting period (end of harvest). The harvested
fruits were separated into healthy fruits and attacked fruits.
The attacked fruits by L. orbonalis were recognizable in the
field by the holes corresponding to the points of entry of the
larvae of stage 1 or exit of the larvae of last stage. Healthy
fruits were those with no lesions caused by L. orbonalis.
The attack rate (Txi) due to L. orbonalis was calculated
from the ratio: number of fruits attacked by L. orbonalis (n) on
the total number of fruits per plant during each harvest
(N)*100, according to the formula:
PDI or AR (%)= (ni/N)*100
Where: PDI/AR
= Percent Index Damage or Attack rate
(%);
ni = Total number of attacked fruits;
N = Total number of fruits on plant.
Fruit attack rates due to L. orbonalis were evaluated
according to the harvests and seasons of the year throughout
the study period. It should be noted that attack rates were
evaluated during harvest and during field observations; the
fruits with exit holes were evaluated directly in the field.
Harvested fruits (mature and consumable), in addition to the
presence of the holes, were dissected before being incubated to
reassure themselves of the presence of Leucinodes orbonalis
larvae.
2.6.3. Influence of Weight, Length and Diameter of the
Attacked Fruit of Adults of Leucinodes orbonalis
During the incubations of the attacked fruits following the
harvests, the weight and the size (length and diameter) of
each fruit were taken before each incubation. Thus, the
average weight and mean size (mean length and diameter) of
the incubated fruits were correlated with the abundances of
emerging L. orbonalis in order to note the influence of these
parameters on their populations. The average number of L.
orbonalis individuals per kg of fruit was also noted. The
weight of the fruit was taken using a “Philips” brand gram
scale and the size taken using a Vernier caliper.
2.6.4. Influence of Temperature and Precipitation on
Average Field Damage Due to Leucinodes orbonalis
Average field damage (following observations and counts
of fruits with holes in or out of L. orbonalis larvae) was
correlated with total rainfall, mean temperature and mean
relative humidity of the study site.
2.7. Data Analysis
The data were encoded using the Excel 2003 software as
well as to calculate the average abundances of L. orbonalis
adults obtained per incubated fruit. After a logarithmic
transformation of the abundances, we compared the averages
using the Analysis of Variances (ANOVA) test contained in
the GLM procedure of the "Statistica" software version 8.0
(2007), followed by a multiple comparison of the averages 2
to 2 by a Tukey HSD test if there are significant differences.
The Spearman correlation coefficient r between two variables
was calculated for mean weight and size (length and diameter)
of the incubated fruits and average abundance of L. orbonalis.
All the results were assessed at the significance level p <0.05.
3. Results
3.1. Temporal Fluctuation of Emerged Leucinodes orbonalis
Populations on Eggplant Fruits
3.1.1. Fluctuation of Leucinodes orbonalis Populations
According to the Harvests
The emerged populations of Leucinodes orbonalis
during incubations showed significant differences from
one harvest to another (F
Har ves t
(5, 325) = 27.038, p
<0.001). T hey were higher at the 2nd harvest (in August)
with an average value of 4.37±0.66 individuals per fruit
per harvest (Min=2.98, Max=5.75, N=12) corresponding
to the short dry season (Table 1 ). This number decreases
pro gressively with the arrival of the rains at the 6th
harvest (Sep tember) with a lower mean abundance of 1.19
± 0.08 individuals per fruit per harvest (Min=1.02,
Max=1.36, N=67) (Septemb er) corresponding to the long
rainy season. The average number of individuals
(cumulative harvests) was 2.43±1.33 ind ividuals per fruit
(Min=1.88, Max=2.98) (Table 1).
Table 1. Mean (±SE) number of Leucinodes orbonalis per fruit per harvest (H).
Harvests M.N of Leucinodes orbonalis/fruit/harvest M.N of L. orbonalis (-95.00%) M.N of L. orbonalis (+95.00%) N
H1 1.41±0.19 a (0.99-1.84) 0.99 1.84 12
H2 4.37±0.66 b (2.98-5.75) 2.98 5.75 19
H3 4.03±0.38 b (3.25-4.80) 3.25 4.80 35
H4 2.00±0.15 a (1.71-2.31) 1.71 2.31 113
American Journal of BioScience 2023; 11(3): 71-81 75
Harvests M.N of Leucinodes orbonalis/fruit/harvest M.N of L. orbonalis (-95.00%) M.N of L. orbonalis (+95.00%) N
H5 1.59±0.12 a (1.35-1.83) 1.35 1.83 85
H6 1.19±0.08 a (1.02-1.36) 1.02 1.36 67
Mean±SD 2.43±1.33 1.88±0.94 2.98±1.74 55.16±38.02
Note: H=Harvest, M.N=Mean number, Std. Err=Standard Error, SD=Standard Deviation, Mean number of Leucinodes orbonalis/fruit followed by the different
letter (s) differ significantly at (p<0.05, HSD Tukey test) and Mean Number of Leucinodes orbonalis/fruit followed by the common letter (s) do not differ
significantly (p≥0.05, HSD Tukey test).
3.1.2. Fluctuation of Leucinodes orbonalis Populations
According to the Seasons
The emerged populations of Leucinodes orbonalis showed
significant differences from one season to the next (F
Season
(1,
329) = 15.002, p <0.001). The average number of L. orbonalis
individuals was higher during the short dry season with an
average value of 3.22 ± 0.48 individuals per fruit per season
(Min = 2.24, Max = 4.21, N = 31) and lower during the large
rainy season with 1.94 ± 0.09 individuals per fruit per season
(Min = 1.75, Max = 2.12, N = 300) (Figure 3). Rainfall
significantly reduced the number of Leucinodes orbonalis
individuals during this study.
Note: SDS=Short Dry Season; LRS=Long Rainy Season.
Figure 3. Mean (±SE) number of Leucinodes orbonalis per fruit per season.
3.2. Damage Index on Solanum aethiopicum Fruits Due to
Leucinodes orbonalis
3.2.1. Damage Index (ID) Per Harvest
The average damage due to L. orbonalis did not vary
significantly from one harvest to another (F
Harvest
(5, 332) =
0.550, p = 0.737) as well as the average total number of fruits
per plant (F
Harvest
(5, 87) = 0.78, p = 0.57). On the other hand,
the average total number of attacked fruits per plant varied
significantly (F
Harvest
(5, 86) = 5.18, p <0.001). Indeed, for an
average value of the total number of harvested fruit of 8.00 ±
1.96 / plant (Min = 2.94, Max = 13.05, N = 12), the highest
average attack rate due to L. orbonalis was 13.05 ± 4.10%
(Min = 4.01, Max = 22.09, N = 12) corresponding to the short
dry season (August) (Table 2). The lowest average attack rate
was 9.04 ± 2.49% (Min = 4.07, Max = 14.01, N = 85) for an
average value of the total number of harvested fruit of 11.07 ±
1.73 (Min = 7.33, Max = 14.80, N = 85) (Table 2).
Table 2. Mean attack rate (%) due to Leucinodes orbonalis on harvested fruits.
Harvests M.T.N.F/plant/ (-95%-+95%) M.T.N.A.F/plant/ (-95%-+95%) M.A.R (%) (-95%-+95%) N
H1 8.00±1.96 (2.94-13.05) 2.00±0.44 (0.85-3.14)a 13.05±4.10% (4.01-22.09) 12
H2 12.11±2.03 (7.42-16.79) 2.37±0.56 (1.03-3.71)a 9.94±4.00% (1.30-15.20) 19
H3 13.64±1.84 (9.74-17.55) 2.05±0.22 (1.59-2.52)ac 9.43±2.34% (4.66-14.20) 35
H4 10.36±1.51 (7.23-13.48) 4.52±0.50 (3.48-5.55)ad 12.80±2.56% (7.73-17.88) 113
H5 11.07±1.73 (7.33-14.80) 6.07±1.24 (3.37-8.76)bd 9.04±2.49% (4.07-14.01) 85
H6 11.00±1.44 (7.99-14.00) 3.04±0.52 (1.94-4.14)a 9.19±1.76% (5.67-12.72) 67
Mean±SD 11.03±1.79 3.34±1.57 10.57±1.76% 55.16±36.02
Note. H=Harvest, Std. Err=Standard Error; SD=Standard Deviation; M.T.N.F/plant/harvest=Mean total number of fruits per plant per harvest;
M.T.N.A.F/plant/harvest=Total number of attacked fruits/plant/harvest; MAR=Mean attack rate, Mean number of T.N.A.F/plant followed by the different letter
(s) differ significantly (p<0.05, HSD Tukey test) and Mean number of T.N.A.F/plant followed by the common letter (s) do not differ significantly (p≥0.05, using
HSD Tukey test).
76 Pierre Stephan Elono Azang et al.: Incidence and Populations Fluctuation of Leucinodes orbonalis Guen. 1854
(Pyralidae) on African Eggplant (Solanaceae) and Their Relationship with Abiotic Factors
3.2.2. Damage Index Per Season
The damage due to Leucinodes orbonalis did not vary
significantly from one season to another (F
Season
(1, 336) =
0.194, p <0.659). They were 8.87 ± 3.03% (Min = 2.72, Max =
15.03, N = 38) in the short dry season and 10.54 ± 1.28% (Min
= 8.00, Max = 13.07, N = 300) in the long rainy season. The
total number of fruit per plant per season also did not vary
significantly from one season to another (F
Season
(1, 336) =
0.219, p <0.64). This average number was 10.46 ± 1.50 fruits
per season (Min = 7.24, Max = 13.68, N = 15) in the short dry
season and 11.38 ± 0.80 fruits per season (Min = 9.77, Max =
12.99, N = 78) in the long rainy season (Figure 4).
Note: SDS=Short Dry Season; LRS=Long Rainy Season; TNF=Total Number of Fruits
Figure 4. Mean (±SE) total number of fruit per plant and attack rate due to Leucinodes orbonalis on eggplant fruits per season.
3.3. Correlation Matrix Between Mean of Leucinodes
orbonalis Populations Per Fruit and Means Weight,
Length and Diameter
3.3.1. Average Weight, Length and Diameter of an Incubated
Fruit per Harvest
Mean weight, mean length, and mean diameter of an
attacked and incubated fruit varied significantly from one
harvest to another (F (5, 325) = 5.893, p <0.001; F (5, 325) =
7.71, p <0.001 and F (5, 325) = 7.84, p <0.001 respectively).
The highest average weight, mean length and mean diameter
were obtained at the second and third harvests with mean
values of 36.15 ± 6.87 g (Min = 21.71, Max = 50.59, N = 19)
and 40.20 ± 4.40 g (Min = 31.34, Max = 49.14, N = 35) for the
average weight; 4.03 ± 0.30 cm (Min = 3.39, Max = 4.67, N =
19) and 3.86 ± 0.15 cm (Min = 3.54, Max = 4.19, N = 35) for
the average length and 4.15 ± 0.34 cm (Min = 3.42, Max =
4.88, N = 19) and 4.12 ± 0.20 cm (Min = 3.71, Max = 4.53, N
= 35) for the average diameter of the attacked fruits
corresponding to the end of the short dry season (end of
August) and at the beginning of the long rainy season (early
September) (Table 3). The lowest values for the average
weight, length and diameter of the attacked fruit were
obtained during the last harvest, i.e 16.65 ± 2.27 g (Min =
12.11, Max = 21.19, N = 67); 2.68 ± 0.14 cm (Min = 2.39,
Max = 2.96, N = 67) and 2.65 ± 0.14 cm (Min = 2.35, Max =
2.94, N = 67) respectively (Table 3).
Table 3. Means weight (g), length (cm) and diameter (cm) variation of incubated fruits per harvest.
Harvests M.W (g) of attacked fruits M.L (cm) of attacked fruits
M.D (cm) of attacked fruits
M.N of L. orbonalis per fruit
N
H1 23.83±3.70ad (15.68-31.97) 3.41±0.27a (2.81-4.01) 3.27±0.30ab (2.61-3.93) 1.41±0.19a (0.99-1.84) 12
H2 36.15±6.87ab (21.71-50.59) 4.03±0.30ab (3.39-4.67) 4.15±0.34ad (3.42-4.88) 4.37±0.66b (2.98-5.75) 19
H3 40.20±4.40ab (31.25-49.14) 3.86±0.15ab (3.54-4.19) 4.12±0.20ad (3.71-4.53) 4.03±0.38b (3.25-4.80) 35
H4 29.56±2.41a (24.77-34.35) 3.27±0.11a (3.05-3.49) 3.44±0.12a (3.19-3.68) 2.00±0.15a (1.71-2.31) 113
H5 25.37±2.31ac (20.79-29.99) 3.08±0.12ac (2.85-3.32) 3.22±0.15acb (2.91-3.52) 1.19±0.12a (1.35-1.83) 85
H6 16.65±2.27adc (12.11-21.19)
2.68±0.14adc (2.39-2.96) 2.65±0.14ab (2.35-2.94) 1.19±0.08a (1.02-1.36) 67
Mean±SD 28.62±8.18 3.38±0.47 3.47±0.54 2.43±1.33 55.16
Note. H=harvest, Std. Err=Standard Error; S.D=Standard Deviation, M.W=Mean weight, M.L=Mean length, M.D=Mean diameter, M.N=Mean number, Mean
number of T.N.A.F/plant followed by the different letter (s) differ significantly (p<0.05, HSD Tukey test) and Mean number of T.N.A.F/plant followed by the
common letter (s) do not differ significantly (p≥0.05, HSD Tukey test).
American Journal of BioScience 2023; 11(3): 71-81 77
3.3.2. Correlation Matrix
The data in Table 4 indicated that the mean number of L.
orbonalis per fruit had a significant positive correlation with
mean weight (r=0.39, p<0.01), mean length (r=0.40, p<0.001)
and mean diameter (r=0.41, p<0.001) of attacked fruits. Study
reveal a significant positive correlation between mean weight
(r=0.95, p<0.001) with mean length (r=0.95, p<0.001) and mean
diameter (r=0.96, p<0.001); significant positive correlation
between mean length and mean diameter (r=0.92, p<0.001) of
attacked fruits during June to September 2018 (Table 4).
Table 4. Correlation matrix between means weight (g), length (cm) and diameter (cm) of incubated fruits and mean number of Leucinodes orbonalis per fruit
during the period running from June to September 2018.
Pair of Variables Agronomic characters of fruits
Mean weight (g) of attacked fruits
Mean length (cm) of attacked fruits
Mean diameter (cm) of attacked fruits
Mean Number of
L. orbonalis
Valid N
331 331 331
r-Value 0.39** 0.40*** 0.41***
T(N-2) 7.88 7.86 8.18
p-Level
<0.01 <0.001 <0.001
Mean weight (g)
of attacked fruits
Valid N
331 331
r-Value 0.95*** 0.96***
T(N-2) 57.15 59.21
p-Level
<0.001 <0.001
Mean length (cm)
of attacked fruits
Valid N
331
r-Value 0.92***
T(N-2) 43.36
p-Level
<0.001
Note. *=Significant at the p<0.05 level; **= Significant at the p<0.01 level; ***=Significant at the p<0.001 level; ns=non-significant at p≥0.05, r=Coefficient of
correlation.
3.3.3. Multiple Regression Equations of Mean Number of Leucinodes orbonalis Per Fruit and Mean Weight, Mean Length
and Mean Diameter of Eggplant Fruits
The multiple regression analysis indicated that the physical parameter of attacked fruit contributed for 81.72% (for mean
weight), 81.94% (for mean length) and 86.64% (for mean diameter) of the mean number of L. orbonalis population / fruit during
August to September 2018 (Table 5 and Figure 5).
Table 5. Multiple regression equations of mean number of Leucinodes orbonalis population per fruit and mean weight, mean length and mean diameter.
Pair of Variables
Agronomic characters of fruits MN of L.
orbonalis/fruit
Mean weight (g) of
attacked fruits
Mean length (cm) of
attacked fruits
Mean diameter (cm) of
attacked fruits
MN of L.
orbonalis/ fruit
Y 5.3302x+16.021 0.3103x+2.6544 0.3684x+2.6037 x
R
2
0.8172 0.8194 0.8664 1.00
p-Level 0.01** 0.001*** 0.001***
Note. ***=Significant at p<0.001 level, **=Significant at p<0.01 level ns=non-significant at p≥0.05, R
2
=Co-efficient of determination, Y=ax+b (a and b
constants) = regression equation, p=Significative level, MN=Mean number.
Note: Y=ax + b (a and b, constant)
Figure 5. Multiple regression equations of mean number of Leucinodes orbonalis and mean weight, mean length and mean diameter.
78 Pierre Stephan Elono Azang et al.: Incidence and Populations Fluctuation of Leucinodes orbonalis Guen. 1854
(Pyralidae) on African Eggplant (Solanaceae) and Their Relationship with Abiotic Factors
3.3.4. Mean Weather Parameters and Mean Attack Rate (%) on Field Due to Leucinodes orbonalis and Correlation Between
Abiotic Factors and Attack Rate
Field damage due to Leucinodes orbonalis varied month to month (p<0.05) with the highest values of 9.50% and 10.54%
attacks in June and September corresponding to the rains periods (small and long rainy seasons respectively). The lowest values
were recorded in July and August with 8.87% and 7.79% of attacks corresponding to the short rainy season (Table 6).
Table 6. Means numbers of abiotic factors and attack rate on field and correlation between abiotic factors and attack rate (%) due to Leucinodes orbonalis.
Sampling
Months Sampling date Abiotic factors Attack rate (%) due to
L. orbonalis
Total Rainf. (mm) Mean Temp. (°C) Mean Relative Hum. (%)
June 16 to 30/06/18 150.3 22.2 86.4 9.50bc
July 14 to 28/07/18 50.2 22.4 86.3 8.87ba
August 11 to 25/08/18 70.4 22.3 86.5 7.79a
September 01 to 22/09/18 200.3 22.2 86.3 10.54c
Mean±SD 117.5±64.75 22.3±0.08 86.4±0.09 9.17±1.07
Valid N 4 4 4 4
r-Value 0.80 -0.737 -0.632 1.00
T(N-2) 1.88 -1.54 -1.15
p-Level 0.200 0.262 0.367
Note. SD=Standard deviation, r=Co-efficient of correlation. The Mean number of attack rates affected of the different letters are significantly different according
HSD Tukey test at the threshold of 5%, 18=2018.
3.3.5. Correlation and Multiple Regression Equations Between Abiotic Factors and Attack Rate Due to Leucinodes orbonalis
on Field
The multiple regression analysis indicated that the weather parameter contributed for 75.08% (for total rainfall), 36.36% (for
mean temperature) and 54.62% (for mean relative humidity) of the attack rate due to L. orbonalis on field during June to
September 2018 at Yaoundé (Table 7 and Figure 6).
Table 7. Multiple regression equations between abiotic factors and attack rate (%) due to Leucinodes orbonalis on field.
Pair of Variables Weather parameters Attack rate (%)
due to L. orbonalis
Total Rainfall (mm) Mean Temperature (°C) Mean Relative Humidity (%)
Attack rate (%) due to
L. orbonalis
Y 0.0143x+7.4942 -7.2545x+170.77 -8.8909x+777.13 x
R
2
0.7508 0.3636 0.5462 1.00
p-Level 0.20ns 0.262ns 0.367ns
Note. ns=non-significant at p≥0.05, R
2
=Co-efficient of determination, Y=ax+b (with a and b constants) = regression equation, p=significant level
Figure 6. Multiple regression equation with mean attack rate due to Leucinodes orbonalis and abiotic factors.
American Journal of BioScience 2023; 11(3): 71-81 79
4. Discussion
4.1. Temporal Fluctuation of Leucinodes orbonalis
Population on Eggplant Fruit
The emerged populations of Leucinodes orbonalis per
incubated fruit fluctuated significantly from one harvest to
another (p <0.001) with higher mean abundances at the 2nd
harvest (August) with 4.37 individuals, corresponding to the
wet period. They also fluctuated with study seasons (p <0.001)
with a higher mean value of 3.22 individuals in the short dry
season and a lower value of 1.94 individuals in the long rainy
season. These results showed that the rains of September
considerably reduce L. orbonalis populations in the field.
Others results showed that, the highest values of the average
number of males of L. orbonalis caught on eggplant were
obtained at the 3rd (4.5 individuals) and at the 7th (4.2
individuals) observation in one of the experimental fields in
Bangladesh [29]. In Southeast Asia, L. orbonalis population
are accounted for to increment with normal temperature and
relative humidity [30]. The results on average number of L.
orbonalis individuals (cumulative harvest dates) was 2.43
individuals per fruit. Similar results were obtained in Southern
Cameroon at Koutaba (West Cameroon region) on S.
aethiopicum var. zong (with 2.62 individuals per fruit), var.
jakatu (with 2.16 individuals per fruit) and var. inerme (with
2.35 individuals per fruit) [13]. The results obtained in
Bangladesh find an average value of 3.26 individuals in
experimental field n°1 which is substantially equal to ours
[29]. This would probably be due to the adaptive nature of this
pest under several climatic conditions encountered in different
study areas. Negative relationship between total rainfall and
population of L. orbonalis was recorded during 2011 and 2012
in Pakistan [31].
4.2. Attack Rate Due to Leucinodes orbonalis on Eggplant
Fruits
The damage caused by Leucinodes orbonalis on fruits of S.
aethiopicum did not vary significantly from one harvest to
another (p> 0.05), with slightly higher values of 13.05% at the
1st harvest and 12.80% at the 4th harvest during the wet
period for a low temperature. The percentages of L. orbonalis
infestation on Solanum gilo in Nigeria also did not vary
significantly according to the three harvests in 2007 (p> 0.05)
[32]. Nevertheless, according to the same authors, fruit
infestation in the third planting in 2006 was significantly
higher (p<0.05) (45.98%) than 40.57% and 42.60% recorded
to the first and second planting respectively.
From one season to another, the damage calculated on the
basis of harvests did not significantly vary (p <0.659) with
values of 8.87% in the short dry season and 10.54% in the
long rainy season. Leucinodes orbonalis causes the most
destruction on fruits and is most dynamic amid the late
spring months (from May to August) [33]. Fruit damage in
brinjal by BSFB was higher in May transplanted (spring)
crops than that in July and September transplanted (fall)
crops [4, 34].
4.3. Means Weight, Length and Diameter of Incubated
Fruits and Correlation with Mean Number of
Leucinodes orbonalis
The highest average weights, average lengths and average
diameters of the incubated fruits were 36.15 g, 4.03 cm and
4.15 cm respectively at the 2nd harvest and 40.20 g, 3.86 cm
and 4.12 cm respectively at the 3rd harvest corresponding to
the end of the short dry season and the beginning of the long
rainy season. The average weight of 17.7 g, the average
diameter of 6.8 cm and the average length of 23.4 cm were
reported in Ghana on the fruits of Solanum var. gilo Raddi on
the basis of the Phenotypic Variance Coefficient (PVC) [11].
These results show that the average weight and average
length were significantly higher compared to the agronomic
traits recorded on our species / variety during the study. On
the other hand, the value of the average diameter is close to
that obtained in our study. The results obtained in Southern
Cameroon show that, the average weight, mean length and
average diameter of an incubated fruit were 35 g, 4.17 cm
and 4.4 cm on S. aethiopicum var. zong, results that are
similar to those obtained during our study; evidence that
these different data were collected in the same
agro-ecological zones [15].
Positive and significant correlations were found between
the mean number of adults of L. orbonalis / incubated fruit and
weight (r = 0.39, p <0.01), length (r = 0.40, p <0.001) and
diameter (r= 0.41, p <0.001) of the incubated fruits. Similar
results were presented on the incubated fruits of Solanum
aethiopicum var. zong at Okola (r = 0.98, p <0.001) and at
Koutaba (r= 0.87, p <0.004) between the fruit weight and the
average number of L. orbonalis [15]. Positive and significant
correlations were also found between weight and length (r =
0.95, p <0.00), weight and diameter (r= 0.96, p <0.001), length
and diameter (r = 0.92, p <0.001) of an incubated fruit. These
results corroborate those of Southern Cameroon with
respective values of: r = 0.81, p <0.05 between weight and
length; r= 0.89, p <0.05 between weight and diameter and r =
0.63, p <0.05 between length and diameter [15]. Others results
of Ghana also show the positive and significant correlations
between weight and length (r= 0.75, p <0.01), weight and
diameter (r = 0.81, p <0.01), but rather negative and
non-significant correlations between the length and the
diameter of the fruits (r = -0.29, p> 0.05) because of the very
long length of the fruits [11].
4.4. Total Rainfall, Mean Temperature, Mean Relative
Humidity and Correlation with Attack Rate (%) in Field
Due to Leucinodes orbonalis
The damage from one month of study to another noted in
the field (p <0.05) gave values of the order of 10.54% of attack
in September (rainy periods) and 7.79% in the month from
August (relatively wet period so the small dry season) for 9.40
kg / 30m
2
on the yield. Others results show that, when no trap
was operated in the eggplant fields, fruit damage and fruit
yield were 31.15% and 13.70kg/100m
2
respectively in the
non-IPM blocks and 10.66%, 27.54 kg/100m
2
in the IPM
80 Pierre Stephan Elono Azang et al.: Incidence and Populations Fluctuation of Leucinodes orbonalis Guen. 1854
(Pyralidae) on African Eggplant (Solanaceae) and Their Relationship with Abiotic Factors
blocks respectively [29].
The results showed that L. orbonalis attacks on S.
aethiopicum fruits in the field showed positive and
non-significant correlations with precipitation and negative
and non-significant correlations with mean temperature and
mean relative humidity. In periods of rains, the larvae find the
necessary resource for their optimal development. Rainfall
contributed positively to 75% of attacks caused by L.
orbonalis. Nevertheless, the incidence of L. orbonalis
infestation had a non-significant relationship with temperature,
relative humidity and rainfall on different brinjal varieties at
Pakistan [35, 36]. Some authors also report that L. orbonalis is
generally more active during rains periods on eggplant in
India [33, 37].
5. Conclusion
Rainfall significantly reduced the number of Leucinodes
orbonalis individuals during this study. The physical
parameter of attacked fruit contributed for 81.72% (for mean
weight), 81.94% (for mean length) and 86.64% (for mean
diameter) of the mean number of L. orbonalis population /
fruit and weather parameter contributed for 75.08% (for total
rainfall), 36.36% (for mean temperature) and 54.62% (for
mean relative humidity) of the attack rate due to L. orbonalis
on field.
Acknowledgements
Authors acknowledge the support of Director of Higher
Teacher’s Training College, University of Yaoundé I, for their
material support and cooperation.
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