Journal of Phytopathology and Pest Management 6(1): 32-39, 2019
pISSN:2356-8577 eISSN: 2356-6507
Journal homepage: http://ppmj.net/
∗
Corresponding author:
Eman F. M. Tolba,
E-mail: eman.tolba414@gmail.com
32
Copyright © 2019
Bioactivity of some plant extracts against the
lesser grain borer,
Rhyzopertha dominica
(Fabr.)
(Coleoptera: Bostrichidae)
Eman F. M. Tolba
1*
, Hany A. Fouad
2
1
Plant Protection Department, Faculty of Agriculture, New Valley University, New Valley, Egypt
2
Plant Protection Department, Faculty of Agriculture, Sohag University, Sohag, Egypt
Abstract
Keywords: plant extract, bioassay, lesser grain borer, mixture, mortality, stored pest.
33
1. Introduction
The Lesser Grain Borer,
Rhyzopertha
dominica
(Coleoptera: Bostrichidae) is a
pest of economic significance of whole
cereal grains in the world (Fields, 2006;
Toews et al., 2005; Flinn et al., 2004).
Control of this kind of insect relies
heavily on the use of synthetic
insecticides, particularly organo-
phosphates. Organophosphorous (OP)
insecticides, including malathion, have
been used for post harvest insect control
which have led to problems such as
environmental pollution, increasing costs
of application, pest resistance in many
insect species including lesser grain
borer, and hazard effects on non-target
organisms in addition to direct toxicity to
users (Pimentel et al., 2009; Santos et al.,
2009; Syed et al., 2005; Ma et al., 2004;
Guedes et al., 1996). Plants produce
secondary metabolites that many of
which have insecticidal properties that
can be utilized as an alternative to
synthetic insecticides (Potenza et al.,
2004). Plant extracts and essential oils
have traditionally been used to kill or
repel stored product insects (Bandeira et
al., 2013; Fouad et al., 2012). Plant
extracts of several plants displayed
considerable toxic, fumigant and repellent
effects on adult of
R. dominica
(Ishtiaq et
al. 2016; Arifuzzaman et al. 2014).
Acacia
(
Acacia nilotica
; Family:
Fabaceae), sweet wormwood (
Artemisia
annua
; Family: Asteraceae) and Thuja
(
Thuja orientalis
; Family: Cupressaceae)
are ornamental plants that have been used
as botanical insecticides against stored
grain insect pests (Taghizadeh &
Mohammadkhani, 2017; Forouzan et al.
2016; Lawati et al. 2002). Therefore, the
present study was undertaken to
investigate the insecticidal activity of
A.
nilotica
,
T. orientalis
and
A. annua
extracts against
R. dominica
adult.
2. Materials and methods
Experiments were conducted in the
Entomology Research Laboratory,
Department of Plant Protection, Faculty
of Agriculture, Sohag University, El-
Kwamel, Sohag, Egypt.
2.1 Insect culture
Adults of
R. dominica
were taken from
laboratory mass cultures reared in glass
jars in an environmentally controlled
room at 25 ± 2 °C, 70 ± 10% relative
humidity and 12:12 photoperiod. The
food media used is whole wheat grains.
2.2 Plant materials and extraction
Plants of
A. nilotica
,
A. annua
and
T.
orientalis
were obtained from local
ornamental farm, Sohag, Egypt. Only
leaves were used to obtain the extracts.
Leaves from each tested plants were
handpicked, chopped in pieces, shade
dried and powdered. A weight of 250g of
the leaf powder was separately added to
conical flask and sequentially extracted
with one liter of methanol at room
temperature 30 °C for 24 hours and
filtered using Whatman No.1 filter paper
and again the marc was dissolved in
methanol for three days twice. Pooled
supernatant was then filtered using filter
paper. The extracts were evaporated to
dryness and concentrated using a rotary
evaporator with the water bath set at
40°C (Anshul et al. 2014; Edeoga et al.,
2005). The powdered residue were
transferred into vials and stored at 4°C in
labeled specimen bottles for bioassays.
2.3 Residual film method
The contact toxicity of plant extracts and
34
malathion insecticide was tested
according to the work described by
Fouad and Câmara (2017). Plant extracts
of
A. nilotica
,
A. annua
and
T. orientalis
at 100 and 200 µL mL
-1
concentration
and insecticide malathion 57% EC
(positive control) at 0.0005 (0.5 ppm) and
0.001 µL mL
-1
(1 ppm) concentrations
were used in this test
besides methanol as
(control). To study the effect of plant
extracts mixture against lesser borer, the
extracts were combined in a 1:1 ratio (50
and 100 µL mL
-1
concentration for each
extract) and in 1:1:1 ratio (33.33 and
66.67 µL mL
-1
concentration for each
extract). Using a precision micropipette,
1 mL was applied on the surface of a
Petri dish (9 cm diameter, surface area
63.6 cm
2
). After 15 min, once the solvent
had been evaporated, twenty unsexed
R.
dominica
adults were placed in each Petri
dish. Four replicates were made for each
treatment. The dishes were kept in
controlled room (25 ± 2°C, 65 ± 5% RH
and 12:12 h L: D photoperiod). The
mortality (%) was recorded after 24, 48,
72 and 96 h from starting the test.
2.4 Toxicity on treated wheat grains
The toxicity of plant extracts of
A.
nilotica
,
A. annua
,
T. orientalis
and
commercial insecticide malathion 57 EC
mixed with wheat whole grains were
evaluated by applying 0.5 mL of tested
plant extracts at 2.5 and 5 µL g
-1
concentration and of malathion 57 CE at
0.0001 and 0.0002 µL g
-1
concentration
and the same amount of methanol alone
was applied as control using a precision
micropipette. Equal amounts of 20 g of
wheat whole grains were used in all
treatments. To study the effect of plant
extracts mixtures against lesser borer
feeding on wheat whole grains, the
extracts were combined in a 1:1 ratio
(1.25 and 2.5 µL g
-1
concentration for
each extract) and in 1:1:1 ratio (0.83 and
1.67 µL g
-1
concentration for each
extract). Jars of 200 mL size were used
treatments and solutions or methanol
with the wheat whole grains were shaked
well for 10 sec. After 15 min, once the
solvent had been evaporated, twenty
unsexed
R. dominica
adults were
separated 24h the rearing culture before
the start of experiment. Then insects
were left to feed on wheat grains, treated
or not treated, in controlled room (25±1
ºC, 70±10% RH and 12:12 h L:D
photoperiod). The mortality of beetles
was recorded after 24, 48, 72 and 96 h
from starting the test (Fouad & Câmara
2017; Tavares et al., 2014).
2.5 Statistical analysis
Data from percentage mortality values of
different exposure concentrations and
times were corrected
by Abbot’s formula
(Abbot, 1925), then subjected to analysis
of variance (one-way ANOVA). Means
of treatments were compared at level of
5% probability using the Duncan's
Multiple Range Test.
3. Results
The efficacy of the tested plant extracts
and malathion against
R. dominica
adults
by means of mortality in 24, 48, 72 and
96 h are presented in Table 1 and 2 for
residual film and ingestion tests. All
tested plant extracts were effective to
some degree in reducing the number of
R. dominica
. The results of the present
study indicated that after 96 h of
applications in residual film and
35
ingestion tests, mean percentage of
mortality was higher using indoxacrb
compared with the other treatments. A
mixture of
A. annua+ T. orientalis
gave
high efficacy of tested plant extracts
about 56 % and 60 % of the efficacy of
malathion in residual film and ingestion
tests, respectively. By considering the
mean mortality as a main index,
A. annua
proved to be the most effective of the
three tested plants materials against the
adult, followed by
A. arabica
and
T.
orientalis
. The morality percentages of
R.
dominica
were significantly increased
with the increase of the exposure times in
all tested treatments. In addition,
increasing the concentration level of all
tested treatments increased the mortality
of
R. dominica
adults. The methanol
extract of
A. annua
showed insecticide
activity with 30.0±3.54 % and
38.25±2.35 % (F=35.56;
P
= <0.0001; F=
187.95;
P
= <0.0001) mortality of
R.
dominica
in contact and ingestion tests at
20 % concentration, respectively (Table
1 and 2).
Table 1: Mean values ± standard errors of % mortality calculated for contact toxicity of plant extracts and their mixtures
against Rhyzopertha dominica adults after 24, 48, 72 and 96 h of exposure.
Treatments
Mortality %
100 µL mL
-1
200 µL mL
-1
24 h
48 h
96 h
24 h
48 h
72 h
96 h
Acacia arabica
3.25±1.18 c
5.00±0 cd
11.50±3.12 cd
6.50±1.19 d
8.25±1.18 de
11.50±3.12 de
12.50±3.23 d
Artemisia annua
9.50±0.5 b
10.0±0 b
20.0±0 b
13.75±2.39 c
17.50±3.23 c
20.75±1.49 c
30.0±3.54 bc
Thuja orientalis
1.50±1.19 c
1.50±1.19 d
5.0±2.04 e
5.0±2.04 d
6.50±1.19 e
9.50±2.10 e
12.0±3.14 d
A. arabica+A. Annua
8.25±1.18 b
8.75±1.25 bc
20.0±2.04 b
21.75±4.25 b
28.25±3.12 b
34.0±1.35 b
35.75±2.17 b
A. arabica+T. orientalis
8.25±1.18 b
8.25±1.18 bc
13.75±1.25 c
8.35±1.18 cd
13.75±2.39 cd
16.50±2.36 cd
26.50±3.12 c
A. annua+T. orientalis
5.0±0 bc
8.25±1.18 bc
15.0±2.04 bc
26.50±2.36 b
33.25±1.18 b
35.0±2.04 b
36.50±2.36 b
A. arabica+A. annua+T. orientalis
3.25±1.18 c
5.0±2.4 cd
6.50±1.19 ed
5.0±2.04 d
6.50±1.19 e
8.25±1.18 e
15.0±2.04 d
Malathion
0.0005 µL mL
-1
0.001 µL mL
-1
31.25±3.14 a
41.25±1.25 a
63.50±2.36 a
38.25±1.18 a
48.25±1.18 a
58.25±1.18 a
65.0±3.53 a
F
42.29
109.17
90.24
28.21
55.20
77.07
35.56
P
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
Means ± Standard errors followed by the same letter per column do not differ by the F test (P = 0.05).
Table 2: Mean values ± Standard errors of % mortality calculated for ingestion toxicity of plant extracts and their
mixtures against Rhyzopertha dominica adults after 24, 48, 72 and 96 h of exposure.
Treatments
Mortality %
2.5 µL g
-1
of grain
5 µL g
-1
of grain
24 h
48 h
96 h
24 h
48 h
72 h
96 h
Acacia arabica
6.50±1.19 a
6.50±1.19 cd
8.25±1.18 d
8.25±1.18 e
8.25±1.18 d
9.25±0.48 d
13.25±1.97 de
Artemisia annua
15.0±2.04 bc
15.0±2.04 c
23.25±1.18 c
15.0±2.04 d
18.25±3.12 c
26.50±2.36 c
38.25±2.35 c
Thuja orientalis
5.0±0 d
5.0±0 d
8.25±1.18 d
6.50±1.19 e
6.50±1.19 d
8.25±1.18 d
10.25±0.63 e
A. arabica+A. Annua
10.0±0.82 cd
13.50±2.36 cd
23.50±2.36 c
25.0±3.53 c
33.50±1.18 b
41.75±1.18 b
48.75±1.25 b
A. arabica+T. orientalis
8.25±1.18 d
11.75±3.12 cd
13.50±2.36 d
19.75±1.93 cd
21.50±3.12 c
28.25±1.18 c
34.0±1.35 c
A. annua+T. orientalis
20.0±4.08 b
26.50±6.24 b
41.25±1.25 b
33.50±1.19 b
36.50±1.19 b
43.50±1.19 b
50.50±2.10 b
A. arabica+A. annua+T. orientalis
6.50±1.19 d
6.50±1.19 cd
11.75±1.18 d
6.50±1.19 e
8.25±1.18 d
11.75±1.18 d
17.25±2.50 d
Malathion
0.0005 µL g
-1
of grain
0.001 µL g
-1
of grain
36.50±3.12 a
43.50±1.19 a
63.50±2.36 a
48.25±1.18 a
51.75±1.18 a
63.50±2.36 a
83.50±1.19 a
F
25.24
21.77
125.06
63.81
75.63
166.99
187.95
P
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
Means ± Standard errors followed by the same letter per column do not differ by the F test (P = 0.05).
Maximum mortality was recorded in residual film test with 20% concentration
36
after 96 h of treatment 36.50±2.36 % and
35.75±2.17 % for
A. annua
and
A.
arabica + A. annua
, respectively, while
the minimum mortality was 12.50±3.23
% and 12.0±3.14 % for
A. arabica
and
T.
orientalis
, respectively (Table 1). In
ingestion test, it is evident that the total
mean % mortality of
R. dominica
adults
for treatment
A. annua+T. orientalis
was
41.25±1.25 at concentration of 10% ,
and 50.50±2.10 at concentration of 20%
after 96 h (Table 2).
4. Discussion
Results of the present investigation
indicated that botanical derivatives might
be useful as store insect control agents
for commercial use. The efficiency of the
plant extracts on mortality of
R.
dominica
adults shown in Table 1 and 2
for the different time periods. Mortality
was noted with different individual plant
extracts, mixtures of extracts and
exposure times. The tested plant extracts
showed slight toxicity against
R.
dominica
adults. The most effective
mortality was observed in extract of
A.
annua,
and
T. orientalis
extract was the
least effective against of
R. dominica
(Table 1 and 2). The binary mixtures of
A. annua
with
A. Arabica
or
T. orientalis
synergized the toxicity against
R.
dominica
adult. The toxicity of these
plant extracts against
R. dominica
could
depend on several factors among which
are the chemical composition of the plant
extract and insect susceptibility. Lawati
et al., (2002) reported the extract of
A.
nilotica
in methanol was toxic causing
high mortality to
Callosobruchus
chinensis
. Negahban et al. (2007)
reported that the essential oil of
A.
sieberi
demonstrated fumigant toxicity
to
Callosobruchus maculatus
(L.),
Sitophilus oryzae
(L.) and
Tribolium
castaneum
(Herbst). Artemisinin in the
leaves of
A. annua
, the natural
compound that offered by the plant, have
natural bitterness that gives protection
for stored products against storage pests
(Harnisch, 1980). Essential oil of
A.
annua
was found to inhibit the fecundity
and fertility of the Indian meal moth
Plodia interpunctella
adults (Maggi et
al., 2005). Tripathi et al. (2000) reported
that there was a significant effect of
A.
annua
oil on mortality of
T. castaneum
and
C. maculatus
. Extract from
T.
orientalis
had significantly more
antifeedant activity against
T. castaneum
(Taghizadeh & Mohammadkhani, 2017).
Foliar application of
T. orientalis
extract
on maize was very effective against
Chilo partellus
(Anju and Sharma 1999).
Application of essential oil of
Thuja
occidentalis
lead to 95% mortality of
females and 100% of males of
C.
maculatus
after 6 h exposure (Kéïta et al.
2001). In the present study mixtures of
A. annua
with
A. arabica
or
T. orientalis
are more toxic metabolites against
R.
dominica
adult than these extracts alone.
Synergists are among the most
straightforward strategy for overcoming
metabolic resistance because they can
directly inhibit the resistance mechanism
itself. Efficacy of plant extract or oil is
affected by proportion of chemical
constituents and synergism or
antagonism among them (Sampson et al.,
2005; Hummelbrunner & Isman, 2001).
Synergistic effect of complex mixtures is
very important in plant defense against
37
herbivores. It is often observed that the
mixtures of plant extracts or essential
oils are more efficient than the plant
extract, essential oil or pure compounds
alone (Chaubey, 2012; Ho et al., 1997;
Don-Pedro, 1996). A study to improve
the effectiveness of botanical derivatives
as insecticides will benefit the
agricultural sectors of developing
countries as these substance are not only
of low cost, but also have less
environmental impact in terms of
insecticidal hazard. The mixture of plant
extracts together is more effective due to
the fact that the insecticidal spectrum of
some binary mixtures is increased. More
studies on a larger scale are needed to
develop binary mixtures more effective
to control insect pests in order to be
utilized in an IPM system.
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