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Use of Neem-Based Insecticides Against Southern Armyworm, Spodoptera eridania (Stoll) (Lepidoptera: Noctuidae)

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Laboratory bioassays were carried out to study the insecticidal, antifeedant, developmental, and reproductive effects of three commercial neem oil-based formulations (Pure Neem Oil, Azatrol, and Triple Action Neem) on Spodoptera eridania when used at recommended concentrations. Neem-derived insecticides significantly reduced the food intake of all instars tested, often limiting feeding activity on neem-treated leaf areas to a fraction of that occurring on controls, in both choice and no-choice bioassay tests. Pure neem oil, followed by Azatrol, demonstrated up to 96% antifeedant activity against larvae; consequently, both biopesticides are effective antifeedants. A two-day feeding period on leaves treated independently with Pure neem oil and Azatrol induced prolongation of the second larval instars by 4.5 and 2.7 days, and by 2.4 and 1.3 days for fourth larval instars, respectively. Mortality and pupal ecdysis of S. eridania were also negatively impaired by neem-based biopesticides, with the greatest efficacy attributable for Pure neem oil. When administered orally, commercial formulations induced significant reduction in longevity by 0.8-4.1days, and fecundity of adults was significantly reduced compared to those fed on untreated diet.
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Use of neem-based insecticides against southern armyworm,
Spodoptera eridania (Stoll) (Lepidoptera: Noctuidae)
ABSTRACT
Laboratory bioassays were carried out to study the
insecticidal, antifeedant, developmental, and
reproductive effects of three commercial neem
oil-based formulations (Pure Neem Oil, Azatrol,
and Triple Action Neem) on Spodoptera eridania
when used at recommended concentrations. Neem-
derived insecticides significantly reduced the food
intake of all instars tested, often limiting the
feeding activity on neem-treated leaf areas to a
fraction of that occurring on controls, in both
choice and no-choice bioassay tests. Pure neem
oil, followed by Azatrol, demonstrated up to 96%
antifeedant activity against larvae; consequently,
both biopesticides are effective antifeedants.
A two-day feeding period on leaves treated
independently with pure neem oil and Azatrol
induced the prolongation of the second larval
instars by 4.5 and 2.7 days, and by 2.4 and 1.3 days
for fourth larval instars, respectively. Mortality
and pupal ecdysis of S. eridania were also negatively
impaired by neem-based biopesticides, with the
greatest efficacy attributable for pure neem oil.
When administered orally, commercial formulations
induced significant reduction in longevity by
0.8-4.1 days, and fecundity of adults was
significantly reduced compared to those fed on
untreated diet.
KEYWORDS: southern armyworm, Spodoptera
eridania, biopesticide, neem oil, antifeedant
INTRODUCTION
One of the principal constraints in increasing crop
productivity in the world is infestation by pestiferous
insects. Southern armyworm, Spodoptera eridania
(Stoll), is an example of such destructive pests. It
attacks a very broad range of hosts, including
vegetable, fruit, and ornamental crops.
As a consequence of the lack of knowledge and
the absence of alternative plant protection strategies
in many countries, the most frequent method used
by growers to protect their crops from pest attack
is the use of traditional chemical pesticides.
In view of the well-known detrimental effects of
synthetic insecticides [1], development of sustainable
and non-polluting plant protection strategies has
become important for the global populations’ food
supply, and ecosystem conservation. Thus,
some producers are progressively adopting more
environment friendly integrated pest management
and organic farming approaches, which are
increasingly considered to be core practices in
plant protection [2].
Many pesticides of botanical origin are characterized
by their relatively low toxicity, biodegradability
and other factors that make them acceptable in
the environment, and which would favor their
incorporation into integrated pest management
programs [3]. With the robust growth of safer
insecticides in the global pesticide market,
azadirachtin, a steroid-like tetranortriterpenoid derived
from the Indian neem tree (Azadirachta indica),
1Jordan University of Science and Technology, Faculty of Agriculture, Department of Plant Production,
P. O. Box (3030), Irbid 22110, Jordan. 2University of Florida, Institute of Food and Agricultural Sciences,
Department of Entomology and Nematology, P. O. Box 110620, 1881 Natural Area Drive, Gainesville,
Florida 32611, USA
Hail K. Shannag1, John L. Capinera2 and Nawaf M. Freihat1
Trends in
Entomology
Vol. 9, 2013
46 Hail K. Shannag et al.
mortality, fecundity and longevity. Use of such
innovative, effective, and practical options could
offer the opportunity for further use of sustainable
pest management systems for many other crops,
particularly where traditional pesticide inputs are
undesirable or restricted.
MATERIAL AND METHODS
Plant and southern armyworm rearing
The experiments were carried out at Department
of Entomology and Nematology, University of
Florida, Gainesville, Florida, USA. A stock culture
of S. eridania was established from larvae collected
from a farm near Gainesville, Florida, immediately
before the research, and the progeny used
subsequently throughout the studies. They were
moved from their natural plant diet to synthetic
bean-based diet [14] shortly before studies
commenced, and maintained on this diet for the
duration of the investigations.
Adults of southern armyworm were kept in screen
mating cages (50 cm x 50 cm x 70 cm) and nourished
on a 20% honey solution as a source of energy
that was offered in a small plastic bottle with screw
plastic cap. An absorbing wick (1 cm in diameter
x 7.5 cm long) was inserted through a hole punctured
in the lid of feeding bottle. The artificial diet used
to feed adults was replaced as appropriate. Pieces
of folded wax paper were placed in the rearing cage
for egg-laying. Oviposition substrates occupied
with eggs were removed daily and maintained
independently in a plastic container. After hatching,
neonate larvae were reared on the artificial bean-
based food until they pupated. A thick layer of
vermiculite furnished at the bottom of a cylindrical
plastic container (25 cm diameter x 10 cm height)
was provided for pupation. Insect rearing and all
bioassays were conducted in the same experimental
conditions, in a controlled room at 25 ± 1 °C and
long-day photoperiod of 16:8 h (L:D).
Neem-based insecticides
Commercially formulated Azatrol (1.2% azadirachtin)
manufactured by Pbi/Gordon Corporation, Kansas
City, Missouri, USA; Triple Action Neem Oil
(70% neem oil) from Southern Agricultural
Insecticides Inc, Palmetto, Florida, USA; and Pure
Neem Oil (100% neem oil) produced by Dyna-Gro,
is uniquely positioned as a key insecticide in the
botanical market segment [4]. Based on its
advantages, there is increasing interest in the use
of azadirachtin to suppress phytophagous insects,
particularly in cropping systems that rely on natural
enemies as a major component of integrated pest
management. In spite of there being commercial
neem-based products labeled for many insect
species, their efficacy under field and greenhouse
conditions has been proven to be variable [5].
Evaluation of azadirachtin is confounded by the
insect growth regulator actions of neem products
[6]. Similarly, the impacts of neem-based pesticides
on many other aspects of insect biology, including
feeding behavior, reproduction, growth, fitness
and mobility of the insects seem to vary among
insects, as well as challenging to assess. The
variable effects of azadirachtin could be attributed
to the insect species tested, the application dose,
and application [7]. Other components in neem
extracts, along with the methods of extraction,
storage conditions, origin of neem, or contamination
with mycotoxins, can also influence performance [3].
Even with the several advantages of neem-based
insecticides, their use may be limited by their
susceptibility to environmental variability, particularly
by photodegradation. As neem extracts are mainly
applied as spray treatments onto the crop canopy,
they are subject to environmental influences,
sometimes resulting in erratic levels of success on
a variety of arthropod pests [8]. Therefore, there
are many efforts underway to stabilize such
biopesticides by using photostabilizers to achieve
persistence as desired for specific control situation.
Insecticidal adjuvant formulations such as stilbene-
derived optical brighteners, particularly Tinopal
LPW, has been used over the past decade in some
bio-pesticide formulations, mainly with baculoviruses
[9, 10, 11]. Soil treatment making use of the
systemic properties of azadirachtin is another option
that may lessen instability and prolong persistency
of the neem-derived insecticides, although this
approach is accompanied by higher costs [12, 13].
Therefore, this study was performed to evaluate
the response of the southern armyworm to three
commercially formulated biopesticides, namely
Azatrol (EC), Triple Action Neem Oil, and Pure
Neem Oil, under laboratory conditions. We assessed
their potential effects on feeding, development,
Effect of neem-derived insecticides on Spodoptera eridania 47
Larvicidal and pupicidal activity
Water-based solutions of Triple Action Neem Oil,
Azatrol, and Pure Neem Oil were applied at
recommended concentrations using a leaf dip
method. Treated cucumber leaves were presented
to 25 insects in the second or fourth instar after a
12 h period of starvation. A feeding period of two
days was chosen to ensure that all larvae were fed.
Afterwards, the larvae were transferred into new
plastic containers and provided continuously with
plain artificial diet until they fully developed.
Once larvae molted to the pupal stage, pupae were
kept in new containers with a layer of vermiculite
as a pupation substrate until they reach the
adulthood. Six replicates were used for each
treatment with 25 larvae per replicate (150 larvae/
treatment). Larval mortality, length of larval
development, and proportion of pupae developing
into adults were recorded. Percent mortality was
calculated according to Abbott’s formula (Abbott,
1925): corrected mortality = [(% mortality in
treatment - % mortality in control)/(100 - % mortality
in control)] x 100. Pupicidal activity was computed
by subtracting the number of emerging adults from
the total number of pupae.
Fecundity and longevity of S. eridania adults
Effects of ingestion of commercially formulated
neem products on the fecundity and life span were
studied by allowing recently emerged adults (24 h
old) to feed on 20% honey solution containing
either Triple Action Neem Oil, Azatrol, or Pure
Neem Oil at concentrations of 7.8 ml, 31.2 ml,
and 7.8 ml per liter, respectively. Control insects
were offered plain 20% honey solution. Groups of
five pairs of adults (5 females and 5 males) were
confined in an aluminum screen cage (20 cm x
20 cm x 20 cm) containing folded wax paper as
oviposition substrate. Insecticide solutions were
offered continuously to adults in a small plastic
bottle with screw cap (5 cm diameter x 5 height)
provided with a piece of absorbant wick through
the lid. Diet solutions were replaced every two
days to prevent fungal growth. Three replicates,
each replicate consisting of one screen cage with
five pairs of adults, were used per neem product,
plus a control. Longevity was determined by
checking adult moths daily until death occurred,
and the number of eggs they produced was
recorded daily until the death of all adults.
San Pablo, California, USA, were used in all
experiments as water-based solutions at recommended
field concentrations: 31.2 ml/l for Azatrol, 7.8 ml/l
for Triple Action Neem Oil, and 7.8 ml/l for Pure
Neem Oil.
Antifeedant bioassays
Feeding responses of S. eridania larvae to either
treated or untreated leaf disks were examined by
no-choice, choice, and multiple choice methods.
Fresh cucumber leaf disks measuring 28.3 cm2
were punched immediately before application of
treatment solutions to minimize changes in leaf
quality and then dipped for a minute into the
prepared solutions of formulated neem-derived
chemicals. Leaf disks immersed only into water
were used as a control. All treated leaf disks were
left dry at room temperature.
Plastic Petri dishes (9 cm x 1.5 cm) lined at the
bottom with wet filter paper were used for no-
choice tests, whereas cylindrical plastic containers
(25 cm x 10 cm) with moist tissue at the bottom
were applied for choice and multiple-choice tests
in order to maintain high humidity and to avoid
early drying of the leaf disks. In no-choice tests,
one leaf disk and a single, second, third, or fourth
instar larvae were transferred individually into Petri
dish after a 12 h period of starvation and allowed
to feed freely for 24 h. Leaf area consumed by
each larva in both treated and control leaves was
measured using a leaf area meter (LI-3000A,
LI-COR, Lincoln, Nebraska, USA).
In choice tests, one treated and one control disk
were placed in each container containing either a
single, second or fourth instar larva. The distance
between the two disks was approximately 10 cm.
In order to determine the neem-based product with
the most effective antifeedant activity, multiple-
choice bioassays that included all the four
treatments in the same container were carried out
for 24 h for all bioassays. For every chemical
substance evaluated and each instar larva, 10 larvae
with three replicates were used. The consumed
area in all tests was obtained by subtracting the
remaining area from the initial area of each leaf
disk. The percentage of antifeedant activity was
calculated using the formula: antifeedant index =
[(leaf area consumed in control - leaf area consumed
in treatment)/leaf area consumed in control] x 100.
48 Hail K. Shannag et al.
showed the least inhibition of food intake (19.8%)
with the antifeedant index estimated as 14.8%.
Pure Neem Oil and Azatrol were much more
effective antifeedants, displaying antifeedant
activity of 94.8% and 80.9% (Table 2), with
larvae consuming only 0.5% and 3.2% of leaf
area, respectively (Table 1).
The same trends, but at a lower magnitude, were
observed by the fourth instars, which were less
sensitive to Triple Action Neem Oil behaviorally,
displaying a slight inhibition of leaf consumption
(3.8% antifeedancy), whereas Pure Neem Oil and
Azatrol markedly reduced food consumption by
S. eradania larvae by 78.4 and 65.6%, respectively.
Feeding activity in choice tests
On average, the second and fourth instars of
S. eridania preferred significantly more untreated
leaf disk material when presented simultaneously
with treated, but at the same time they did not
reject the neem-treated food completely (Table 3).
Data were subjected to analysis of variance by
means of SAS software version 9.2 [15] and means
were compared using the Least Significance
Differences (LSD) test at P 0.05. Mortality counts
of S. eradania were evaluated by using Abbot’s
formula [16]. Values of antifeedant activity were
transformed to log10(X -100).
RESULTS
Feeding activity in no-choice test
There is strong evidence that neem-based
products inhibited food intake in the different
instars evaluated using no-choice tests (Table 1).
On an average, 8.3% of untreated leaf disks of
cucumber plants were consumed by the second
instars, whereas the larvae consumed only 0.3-6.5%
of treated leaf disks, depending on the chemical
tested. The antifeedant index was 16.6% for
Triple Action Neem Oil, 96.3% for Pure Neem
Oil and 89% for Azatrol (Table 2).
Neem-based products also significantly reduced
feeding by third instars. Triple Action Neem Oil
Table 1. Average leaf area (cm2) and proportion of cucumber disks consumed by S. eridania
larvae in no-choice bioassays.
Treatments 2nd instar 3rd instar 4th instar
Control 2.34 a (8.3%) 6.67 a (23.6%) 20.13 a (71.1%)
Triple Action Oil 1.84 b (6.5%) 5.60 b (19.8%) 19.36 a (68.4%)
Azatrol 0.26 c (0.9%) 0.91 c (3.2%) 7.67 b (27.1%)
Pure Neem Oil 0.08 c (0.3%) 0.14 d (0.5%) 4.18 c (14.8%)
LSD 0.24
DF 3, F 178.33
LSD 0.05
DF 3, F 336.1
LSD 1.53
DF 3, F 221.7
Mean values of leaf consumption within column for each instar followed by the same letter are not
significantly different at P 0.05.
Table 2. Antifeedant indexes and their proportional feeding reduction for the three neem-based
pesticides when evaluated on different instars of S. eridania.
Treatments 2nd instar 3rd instar 4th instar
Triple Action Oil 4.67 a (17.4%) 4.72 a (14.4%) 4.62 a (2.4%)
Azatrol 5.23 a (89.0%) 5.22 b (84.6%) 5.10 b (64.0%)
Pure Neem Oil 5.28 b (96.3%) 5.29 c (98.2%) 5.18 c (78.3%)
LSD 0.174
DF 2, F 30.18
LSD 0.056
DF 2, F 236.2
LSD 0.049
DF 2, F 297.5
Mean antifeedant indexes within column for each instar followed by the same letter are not significantly
different at P 0.05. Data are transformed to log10(X -100).
Effect of neem-derived insecticides on Spodoptera eridania 49
insecticides exerted a deleterious effect on feeding
behavior that was statistically superior to that of
the Triple Action Neem Oil and control treatments.
In comparison to the control, the average leaf
consumption of treated leaf disks by second
instars was reduced by 85.2% for Triple Action
Neem Oil, 95.6% for Pure Neem Oil, and 94.8%
for Azatrol. The second and fourth instar larvae
behaved similarly with respect to the treatments.
For trials with fourth instars, leaf consumption of
treated disks was reduced by 72.9% for Triple
Action Neem Oil, 97.5% for Pure Neem Oil, and
96.2% for Azatrol in comparison with the control.
However, the amount of leaf material consumed
by larvae exposed to leaves treated with Triple
Action Neem Oil did not differ significantly from
those of untreated leaves. In contrast, Pure Neem
Oil and Azatrol induced significant inhibition of
food intake, with about 20 times as much leaf area
consumed in untreated foliage as compared to
neem-treated.
Feeding activity in multiple-choice test
The multiple-choice bioassays demonstrated that
Pure Neem Oil and Azatrol were the most effective
feeding deterrents for the second and fourth
instars of southern armyworm (Table 4). Both
Table 3. Total area of consumed cucumber leaf (cm2) and proportion
consumed by S. eridania in choice bioassays.
Treatment 2nd instar 4th instar
Control
Triple Action Oil
0.86 a (3.0%)
1.01 a (3.5%)
12.63 a (44.6%)
9.69 a (34.2%)
LSD 0.49
DF 1, F 1.01
LSD 5.27
DF 1, F 1.24
Control
Azatrol
2.16 a (7.6%)
0.10 b (0.3%)
21.95 a (77.6%)
1.25 b (4.4%)
LSD 0.29
DF 1, F 203.10
LSD 2.68
DF 1, F 236.7
Control
Pure Neem Oil
1.62 a (5.7%)
0.06 b (0.7%)
17.51 a (61.9%)
0.72 b (2.5%)
LSD 0.20
DF 1, F 245.0
LSD 1.74
DF 1, F 372.2
Means within column for each paired control and treatment values for each
instar followed by the same letter are not significantly different at P 0.05.
Table 4. Total leaf area (cm2) consumed by S. eridania larvae in multiple-
choice bioassays.
Treatment 2nd instar 4th instar
Control 2.32 a 15.53 a
Triple Neem oil 0.34 b 4.63 b
Azatrol 0.12 b 0.65 c
Pure Neem oil 0.11 b 0.43 c
LSD 0.28
DF 3, F 114.2
LSD 2.56
DF 3, F 60.2
Means within column followed by the same letter are not significantly different
at P 0.05.
50 Hail K. Shannag et al.
lesser effects, also leading to significant decreases in
the number of adults emerging from the pupal stage.
The effects of neem-derived insecticides on the
development time of S. eridiana are presented in
Table 6. Increased larval development periods were
observed among second instars fed with neem-
treated food for 48 h when compared to those kept
on untreated food, although the degree of delayed
development varied among treatments. The Pure
Neem Oil and Azatrol treatments induced significant
prolongation of larval development time relative
to the control, extending mean development time
by 4.74 and 2.69 days, respectively. On an average,
Triple Action Neem Oil delayed mean larval
development for less than a day, which did not
significantly differ from control treatment.
In contrast, the development time of the fourth
instars did not differ significantly between the control,
Triple Action Neem Oil, and Azatrol. However, Pure
Mortality, development and pupal ecdysis
When larvae were fed cucumber leaves dipped in
commercial neem-based products at recommended
concentrations, some treatments induced mortality
(Table 5). Mean mortality of second instar S. eridania
was 12.2% for Azatrol and 35.5% for Pure Neem
Oil, whereas larval mortality was negligible for
both Triple Action Neem Oil and control treatments.
The same trend, but at higher levels, was observed
for both neem products fed to fourth instars, with
mean mortality of 26.8% for Azatrol and 45.2% for
Pure Neem Oil.
Pupal ecdysis was affected in second instars fed
with neem-treated diet for 24 h and reared to the
pupal stage. However, the effect varied among
products. The greatest reduction in the number of
pupae reaching adulthood was observed for
S. eridania fed on foliage treated with Pure Neem Oil.
The other neem-based products induced similar but
Table 5. Mean S. eridania mortality (%) and successful adult emergence (%) caused by
feeding of second or fourth instars for 24 hours on cucumber leaves treated with different
neem-based pesticides.
Treatment 2nd instar 4th instar Adult emergence
Control 2.67 a 2.67 a 82.88 a
Triple Action Oil 1.94 a 2.67 a 74.78 b
Azatrol 14.67 b 28.77 b 74.82 b
Pure Neem Oil 37.33 c 46.67 c 63.13 c
LSD 6.11
DF 3, F 57.1
LSD 8.12
DF 3, F 61.0
LSD 5.52
DF 3, F 18.84
Means within each column followed by the same letter are not significantly different at P 0.05.
Table 6. Mean development times (days + SE) for second and fourth instars of S. eridania to
complete larval development when fed for 48 hours on diet treated with different neem-
based pesticides.
Treatment 2nd instar (days) 4th instar (days)
Control 14.54 ± 0.14 a 8.66 ± 0.08 a
Triple Action Oil 15.01 ± 0.12 b 9.24 ± 0.08 b
Azatrol 17.07 ± 0.13 c 9.94 ± 0.10 c
Pure Neem Oil 19.20 ± 0.14 d 11.10 ± 0.11 d
Critical T value 1.96
F 264.6
Critical T value 1.96
F 111.3
Means ± SE within column followed by the same letter are not significantly different at P 0.05.
Effect of neem-derived insecticides on Spodoptera eridania 51
active ingredients of neem compounds are non-
volatile substances and the insect must taste them
in order to respond to their presence [19]. Previous
studies revealed that the antifeedant effects caused
by formulated neem-based products appear to
vary with insect species and the formulated neem
product tested. However, similar reductions in
food uptake has been documented for S. lituralis
[20], Salix exigua [21], Mamestra brassicae [22],
and Heliothis viridescens [23] during one- or two-
day feeding periods on leaves treated with
different neem products. The feeding inhibition
has been credited to a direct action of neem
products on the centers of control that regulate
feeding and metabolism [24] and/or the inhibition
of feeding behavior by stimulation of deterrent
chemoreceptors on the mouthparts, or blockage of
input receptors for phagostimulants [25]. However,
azadirachtin and other neem extracts have been
reported not to exhibit antifeedant activity in
Manduca sexta [26] and Peridroma saucia [27].
In addition to having generalized antifeedant
properties, neem-based preparations induce a
variety of disruptive developmental phenomena in
lepidopteran larvae. In the present study, the
second and fourth instars of S. eridania exposed
to Pure Neem Oil and Azatrol took considerably
longer time to reach the pupal stage when
compared to control insects. Such prolonged time
of larval development may be as a result of a
reduction of food intake and lack of converting
food into biomass, as reported for S. littoralis
[28]. Prolonged larval periods were associated
with increased larval mortality in S. eridania, but
Neem Oil significantly prolonged the duration of
larval development for 2.44 days relative to those
maintained on untreated food.
Fecundity and longevity of adults
Fecundity and longevity of S. eridania adults
were significantly affected by prolonged ingestion
of the neem-based products (Table 7). However,
as with other aspects of insect biology, the
magnitude of the effect varied among the products.
Young adults fed with honey solutions containing
neem-derived insecticides at recommended
concentrations produced significantly fewer eggs
over their life span, with egg production decreased
to as little as one-tenth the egg production of
insects fed with untreated foliage, though Triple
Action Neem Oil was not as effective as Azatrol
and Pure Neem Oil. Except in the case of Triple
Action Neem Oil, ingestion of the neem products
significantly decreased adult longevity. Longevity
was reduced by 3.66 d and 4.10 days by Azatrol
and Pure Neem Oil, respectively.
DISCUSSION
Commercially available neem seed extracts have
shown a wide range of bioactivity against insects,
affecting reproductive fitness, hatchability,
molting, development rates, and feeding behavior
[17, 18]. Our results provide clear evidence that
commercially formulated Pure Neem Oil and
Azatrol applied to cucumber leaf disks induce
potent feeding deterrent activity against S. eridania,
though not entirely preventing insect feeding even
in choice tests where the larvae have an alternative
neem-free food source. This is likely because the
Table 7. Effects of neem-derived insecticides on fecundity and mean longevity of
S. eridania adults continuously provided with 20% honey solution mixed with neem-
based products at recommended concentrations.
Treatment Fecundity (5 pairs) Longevity (d)
Control 6621.66 a 9.73 a
Triple Action Oil 2311.67 b 8.93 a
Azatrol 810.33 b 6.07 b
Pure Neem oil 646.33 b 5.63 b
LSD 1731.60
DF 3, F 27.5
LSD 1.40
DF 3, F 16.7
Means within each column followed by the same letter are not significantly different at P 0.05.
52 Hail K. Shannag et al.
Of particular interest would be combinations with
stilbene-derived optical brighteners in order to
improve persistence of azadirichtin and/or other
additives. Also, the differing effectiveness of the
various commercial formulations is of considerable
importance, as their effects on insect biology and
survival can be markedly different.
CONCLUSION
1. Neem-based products evaluated were not able
to completely inhibit food intake of Spodoptera
eridania larvae, but they limited effectively the
feeding activity at different magnitudes depending
on the product.
2. A short-term exposure of S. eridanian larvae to
diet treated with neem-based products prolonged
significantly the duration of larval development.
3. The magnitude of the negative effect on the
larval mortality and pupal ecdysis varied
considerably among neem-drived insecticides tested.
4. A reduction in the fecundity and longevity
followed by the ingestion of commercial neem
oil-based formulations by adult females clearly
indicate that neem-containing products may have
potential for being utilized in food-based traps to
disrupt the biology of some insects.
5. Insecticides based on neem oil seem to have
potential to protect plants from S. eridania, although
additional studies are needed to evaluate their
efficacy under field conditions.
6. Caution in making assumptions on neem products
is advised, as their effects on insect biology and
survival can be markedly different.
ACKNOWLEDGEMENT
I would like to thank Jordan University of Science
and Technology and Fulbright for their financial
support. My gratitude and appreciation are also
extended to Prof. John Capinera at Department of
Entomology and Nematology, University of Florida,
USA for hosting me at his institution and
providing me with all research facilities during
my scholarship.
CONFLICT OF INTEREST STATEMENT
There are no conflicts of interest.
death was delayed a week or longer. Similar effects
were found in S. exigua [23] and Cnaphalocrocis
medinalis treated with different neem-derived
biopesticides [29].
Adults of several important lepidopteran pests
have been reported previously to respond in different
ways to exposure to neem-based products, either
through topical application or by ingestion. As
was observed in other studies, our results clearly
indicate that neem-based products adversely
affected not only the larvae, but the longevity and
the reproductive potential of adults treated orally.
Similar to these results, other commercially
available neem seed extracts adversely affected
the fecundity of several insect pests of significant
importance such as S. littoralis [30], S. exempta
[31], Pieris brassicae [32], and Plutella xylostella
[33]. These consequences could be induced by
interference of neem-based biopesticides with
vitellogenin synthesis or uptake in developing
oocytes, along with the accumulation of proteins
in the eggs that is required for maturation of insect
eggs [31, 34]. Moreover, [35] attributed this effect
to the incorporation of the neem compound into
the eggs during copulation, through sperm transport,
transovarial transport, or both together. Although
our results provide no insight into the mechanism
of disruption, they clearly indicate that neem-
containing products have potential for being
utilized in food-based traps to disrupt the biology
of some insects.
In a recent study, azadirachtin demonstrated a
significant effect on the longevity of S. littoralis
adults only at the higher concentrations [36], whereas
in other investigations, longevity of Phthorimaea
operculella [37], Trichoplusia ni, Peridroma
saucia, and S. litura [38] were not influenced by
azadirachtin. Such disparate outcomes may be
caused by differences in azadirachtin content of
the various parts of the neem tree [39], as well as
inherent differences in the insect species tested.
Adult susceptibility to neem products is not well
understood; the biochemical target sites for neem
are not yet identified.
Commercial formulations of neem-based insecticides
seem to have considerable potential to protect plants
from S. eridania, though additional studies are needed
to evaluate their efficacy under field conditions.
Effect of neem-derived insecticides on Spodoptera eridania 53
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... A previous study determined that commercially formulated pure neem oil and Azatrol applied to cucumber leaf disks at field recommendation rates induced potent feeding inhibition by S. eridania (Shannag et al. 2013). After larvae were removed from diets treated with neembased insecticides, significant increase in their feeding activity (compensatory feeding behavior) was not observed. ...
... Reduction in food intake and the ability to convert food into biomass eventually extends the development time of larvae, probably because the hormonal mechanisms that control the development of most animals can be partly regulated by food intake (Bernard and Lagadic 1993). Prolonged larval duration following exposure to neem was also observed by Behera and Stapathy (1997), Senthil-Nathan and Kalaivani (2005), Senthil-Nathan et al. (2006a), and Shannag et al. (2013). ...
... Second, although mortality can be induced, the level of mortality following a single application of insecticide may not be adequate for insect suppression. For neem products assessed for control of southern armyworm thus far, effectiveness is only moderately suitable (Liburd et al. 2000, Clarke-Harris and Fleischer 2003, Shannag et al. 2013. Third, survivors of neem treatment typically will be smaller and have prolonged development (Shannag et al. 2013). ...
Article
Full-text available
Neem-based insecticides, which have many biological properties, were evaluated for effects on growth, food intake, survival, and nutritional indices of Spodoptera eridonia (Stoll), an important pest of crops in the western hemisphere. Short-term consumption of food treated with neem-derived insecticides by second-instar larvae resulted in suppressed feeding, retarded weight gain, and prolonged development time after the treated larvae had been transferred to untreated synthetic insect diet. Relative consumption rate, efficiency of conversion of ingested food, relative growth rate, approximate digestibility, and assimilation rate of food were reduced after treatment with neem products, especially by the higher concentrations of neem. Efficiency of conversion of digested food was not affected. Also, application of pure neem oil and Azatrol at high concentrations induced 20 and 13.3% larval mortality, respectively, whereas mortality caused by the lower concentrations of both chemicals did not exceed 3.3%. Larvae of S. eridonia were more sensitive to pure neem oil than to Azatrol. These observations may reflect interference of neem with regulation of feeding and metabolism, as well as with anatomy and function of midgut tissues.
... concentrations and leading to the high percentage of mortality. These results matched with that of Shannag et al. (2013) on Spodoptera eridania (Stoll). ...
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Using Diatomaceous Earth in form of Silica nano-particles to control the cotton leaf worm, Spodoptera littoralis (Boisd.) larval stage was tested. The obtained results clarified that the application of silica in nano-form at any of the tested concentration reflected adverse effects on the treated larvae. Feeding larval stage of S. littoralis on castor bean leaves, treated with Silica nano-particles, reduced growth rate, decreased efficiency in exchanging consumed food into body biomass, and decreased larval weight. In addition, the obtained low efficiency of conversion of ingested food (ECI) and/or efficiency of conversion of digested food (ECD) values were observed at the tested concentrations of (1, 2 or 4%), where its consumption leading to retardation in the development, prolongation in the duration and finally death. © 2016, Egyptian Society for Biological Control of Pests. All rights reserved.
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This study characterized and assessed the toxicity of neem extracts obtained by two different methods to manage fall armyworm (FAW) invasion. The extracts, neem seed oil extract (NSOE) and methanolic neem leaf extract (MNLE), were obtained from neem seeds and leaves by Soxhlet extraction and cold maceration respectively. The yields after extraction for neem seed oil and neem leaf extract were 23.92% and 17.05% respectively. The estimated LC50 after 2, 6 and 12 hours for NSOE were 1.78%, 0.97% and 0.68% respectively while LC50 after 2, 6 and 12 hours for MNLE were 2.67%, 2.62% and 1.64% respectively. The results suggest that both extracts have great potential as a natural insecticide for the management of fall armyworm. Hence, farmers should use environmentally friendly insecticides to mitigate FAW damage since their efficacy, economic and environmental recompenses outweigh those of synthetic origins.
Thesis
Abstract A field study was conducted to evaluate the efficacy of several biocompounds (the fungus: Beauveria bassiana and the bacteria Bacillus thuringiensis) and natural compounds (insect growth regulator (Match) and neem extract) in controlling the wheat and barley leafminer. Three rates were used for each compound: the recommended use rate called the average rate and two other rates were lower and higher than the average, in which the plants were sprayed once after one week from the appearance of the pest larvae. The results showed the superior of all compounds used and for all rates of use on the control in reducing the severity of the injury and reducing the number of larvae on the plant leaves. As well as, the insect growth regulator was superior over the other compounds in reducing the incidence and the number of larvae of the pest on the barley leaves a week after the appearance of larvae in the field. The two bio-compounds also showed superiority over the two natural compounds in controlling the pest two weeks after the insect larvae appeared. The results of the effectiveness of these compounds in controlling the pest have been reflected on the yield, as the result of grains and straw biomass for barley for bio-compounds treated plots was two and a half that of the control plots. The study recommends the use of insect growth regulator to control pests at a short-term, and the longer-term use of biocompounds to reduce larval numbers on the vegetative growth
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Using the fungus Beauveria bassiana, the bacterium Bacillus thuringiensis, neem extract and insect growth regulator as bioinsecticides toward sustainable control of cereal leafminer Syringopais temperatella Led. (Lep., Scythrididae) Danial Hjazeen, Ihab Ghabeish and Firas Al-Zyoud Abstract A field study was conducted to evaluate the efficacy of several biocompounds (the fungus: Beauveria bassiana and the bacteria Bacillus thuringiensis) and natural compounds (insect growth regulator (Match) and neem extract) in controlling the wheat and barley leafminer. Three rates were used for each compound: the recommended use rate called the average rate and two other rates were lower and higher than the average, in which the plants were sprayed once after one week from the appearance of the pest larvae. The results showed the superior of all compounds used and for all rates of use on the control in reducing the severity of the injury and reducing the number of larvae on the plant leaves. As well as, the insect growth regulator was superior over the other compounds in reducing the incidence and the number of larvae of the pest on the barley leaves a week after the appearance of larvae in the field. The two bio-compounds also showed superiority over the two natural compounds in controlling the pest two weeks after the insect larvae appeared. The results of the effectiveness of these compounds in controlling the pest have been reflected on the yield, as the result of grains and straw biomass for barley for bio-compounds treated plots was two and a half that of the control plots. The study recommends the use of insect growth regulator to control pests at a short-term, and the longer-term use of biocompounds to reduce larval numbers on the vegetative growth. Keywards: Barley, sustainable control, cereal leafminer, Beauveria bassiana, Bacillus thuringiensis, neem extract, insect growth regulator.
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The effects of three bio-insecticides Azatrol [neem: 1.2% azadirachtin A and B], Molt-X [neem: 3% azadirachtin], and Conserve SC [spinosad; 11.6% spinosyn A and spinosyn D], applied at different concentrations were evaluated on Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) under both laboratory and greenhouse conditions. Laboratory bioassays demonstrated that both neem-based insecticides were repellent to adult whiteflies in a dose-dependent manner. The amounts and frequency of honeydew excretion were significantly reduced up to 0.95 by foliar application of these insecticides at the labeled rate, as compared to untreated plants, with the neem products displaying greater effects on food uptake than spinosad. Reduced fecundity and egg hatch also were associated with these bio-insecticides. The bio-insecticides decreased significantly the survival of nymphs, egg hatch and adult emergence when applied systemically via the roots. However, the impacts of neem-based insecticides on all parameters tested were greater than that of spinosad. The results indicate that the biologically based formulations tested were effective in suppressing whitefly abundance and acting as an efficient repellent, though they were not able to completely inhibit food intake. The repellent and antifeedant activities of such natural products render plants unattractive to B. tabaci, thus potentially reducing the incidence of viral diseases transmitted by this pest. The systemic properties of these formulated biopesticides minimize their rapid degradation by strong ultraviolet light and their adverse effects on non-target organisms.
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The book by Thacker provides an introduction to the subject for students.
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The phytochemical azadirachtin from the neem tree Azadirachta indica was administered to different larval instars of the variegated cutworm, Peridroma saucia orally in artificial diet, topically, or by injection. Nutritional analyses revealed that insect growth inhibitory and antifeedant effects were independent of each other and relative to the level of treatment. Injection of a 2 μg/g body weight dose of azadirachtin to sixth-instar larvae does not lead to starvation. However, substantial developmental anomalies result upon pupation.Ligature experiments demonstrated that head ligation in last-instar larvae, counteracted the azadirachtin-induced interference with pupation, pointing to an “aza-sensitive head factor”. Exogenous application of juvenile hormones I or II or juvenile hormone esterase inhibitor, BEPAT (in order to elevate hormone levels in the larvae) did not counteract any of the effects of azadirachtin treatment. The significance of these results in terms of hormonal events in P. saucia is discussed.
  • S M Martinez
  • H F Van Emden
Martinez, S. M. and van Emden, H. F. 1999, Bull. Entomol. Res., 89, 65-71.
  • M M Adel
  • F Sehnal
Adel, M. M. and Sehnal, F. 2000, J. Insect Physiol., 46, 267-274.