Medicinal Plants and its Impact of Ecology, Nutritional Effluents and Incentive of Digestive Enzymes on Spodoptera litura (Fabricious)
This study having following objectives such as to study the biology, nutritional indices and mid gut enzymes response with three different botanical insecticides and to determined the nature of insecticidal action was examined by dermal, oral and contact treatments. As an alternative to synthetic ones, plants have been received much attention as a source of pesticidal active secondary metabolites such as phenolics, terpenoids and alkaloids. The effect of water extracts prepared from the leaves of Ipomea carnea (Linn.) Convolvulacea and Pedalium murex (Linn.) Pedaliacea and Adhatoda vasica (Linn.) Acanthacea on the biology, nutritional indices and digestive enzymes of the polyphagous pest Spodoptera litura (Fab.) (Lepidoptera: Noctuidae) was investigated. Increased larval and pupal mortality and drastically decreased larval growth were recorded in the experimental extracts treated caterpillars. Feeding efficiency and feacal excrement were also greatly affected. The digestive enzymes profiles were decreased by the plant extract treatments. Furthermore, they were facilitating the active and easy proliferation of the chemicals for the subsequent pathogens of larvae. Among the three application methods tested, oral treatment caused the highest toxicity, followed by topical application and contact treatment. From this study clearly revealed about the active secondary metabolites were arrested or restricted the ecdyseal process during the moulting period of experimental pest. These results suggest that the three plant species tested may have potential for use as natural bio-pesticides.
Received: April 09, 2010;
Accepted: June 08, 2010;
Published: June 24, 2010
The use of conventional insecticides has raised some concern about their threat
to the environment and development of insecticide resistance in insects (Huang
et al., 1998), there is an imperative need for the development of
safer, alternative crop protectants such as botanical insecticides and antifeedants.
Plants are rich sources of natural substances that can be utilized in the development
of environmentally safe methods for insect control (Sedek,
2003). Recently, Briska and Sahayaraj (2009) reported
the botanical plant extracts often consist of complex mixtures of active compounds,
they may show greater overall bioactivity compared to the individual constituents.
The deleterious effects of crude plant extracts on insects are manifested in
several ways, including toxicity (Hiremath et al.,
1997) feeding inhibition (Wheeler and Isman, 2001).
The search for plant-derived chemicals that have potential use as crop protectants
(insecticides, antifeedants and growth inhibitors) often begins with the screening
of plant extracts (Kanat and Alma, 2003; Martin
and Gobalakrishnan, 2005). It has a wide range of host feeding on 12 species
world wide of which 40 species are known from India (Paulraj,
2001). Traditional farmers have been practicing synthetic pesticides to
eliminate the S. litura and hence, it has developed resistance against
almost all the commonly using pesticides in this area. Certain plant families,
particularly Meliaceae, Rutaceae, Asteraceae, Labiateae, Convolvulaceae and
Pedaliaceae are viewed as exceptionally promising sources of plant-based insecticides
(Schutterer, 1990; Isman, 1995).
In the past Sahayaraj et al. (2003) reported
bio-pesticidal property of Chrystella parasitica and Ipomoea carnea
on Achaea janata. The activity of these extracts also suggests that
future exploitation of the materials in to potential insect management chemicals
with a minimum environmental in pest. It interestingly previous Devanand
and Rani (2008) employed with the present study possess antifeedent and
toxicity in the lepidopteran pest. Since the bioactive compounds which are often
active against a limited number of species including specific target insects
are biodegradable to non-toxic products and potentially suitable for use in
integrated pest management programs, they could lead to the development of new
classes of safer insect control agents (Ahmad et al.,
2009) The S. litura (Fab.) (Lepidoptera: Noctuiidae) is a cosmopolitan
and polyphagous pest affecting several crops worldwide causing extensive loss
of agricultural production. Consequently, intensive efforts have been made to
find alternatives, especially insecticides and plant origin which are safe,
effective and environmentally acceptable. Hence, the objectives of this study
are: (1) understand how the biology, nutritional indices and mid gut enzymes
varied in response to different botanical insecticides and (2) to determine
the nature of insecticidal action was examined by dermal, oral and contact treatments.
MATERIALS AND METHODS
Three hundred of Caterpillars and various life stages were collected from the infested groundnut field and subsequently reared in the laboratory on fresh groundnut leaves at 30±1.56°C, 70±10% relative humidity and 12L: 12D photoperiod. Laboratory emerging moths, five males and five females were placed in to oviposition cages and fed with a 10% sucrose solution fortified with a drop of vitamin mixture to enhance the oviposition. The egg batches were removed and kept in Petridishes for hatching. This study was carried out during the year of 2009.
Preparation of Plant Extract
Crude extracts were made from the leaves of four plants: Ipomea carnea
Linn. Pedalium murex (Linn.) and Adhatoda vasica (Linn.). The
aqueous extracts of these plants were made by macerating 100 g of the dry leaves
partially on a mortar and pestle then heating with 250 mL water in sox let apparatus
at 100°C for 24 h. The dissolves solute gave 100 to 150 mL of crude aqueous
extract. The un-dissolved portion was removed and dried in an oven at 80°C
for 6 h to get a constant weight (20, 29, 31, 36 g) for I. carnea, P.
murex and A. vasica, respectively. The weighed aqueous extract was
calculated from the initial weight of the leaves and final weight of the undissolved
portion. The LD50 concentration of I. carnea, P. murex
and A. vasica (w/v) were 3.9, 0.7, 4.5 and 1.3%. The effect of the botanical
extracts were tested using three application methods namely topical application,
oral and contact toxicities.
Five grams of each fresh groundnut leaves were dipped in the LD50
concentration I. carnea, P. aquilinum and A. vasica were
prepared and treated on ground nut leaves for half an hour and air dried thoroughly.
Ten fourth instar larvae of S. litura from laboratory culture were starved
for 6 h and then placed in plastic containers (250 mL capacity) containing plant
extracts treated groundnut leaves. Control larvae were treated with water. The
unconsumed leaves and feacel pellets with in each container were subsequently
weighed after 24 h and then the larvae were provided with fresh untreated groundnut
leaves until pupation.
Whatman (No. 1) filter paper discs (2 cm2) were dipped in the
LD50 concentrations of the plant extracts separately for 15 min and
shade dried for 20 min. Fourth instars larvae of S. litura ten in number
(uniform age and size) were placed in plastic containers (500 mL capacity) containing
plant extract. After 24 h the larvae were removed and placed into plastic containers
containing untreated groundnut shoots and maintained until pupation. Each find
was replicated six times. The impacts of the treatments were measured by recording
larval, pupal and adult mortality larval and pupal developmental periods and
adult longevity. Deformities in the larvae, pupae and adults were also recorded.
Food utilization experiment was conducted in the newly moulted 7 h starved
fourth instar larvae of S. litura. A gravimetric technique was used to
determine weight gain, food consumption and feaces produced. Pre-weighed larvae
(10 larvae/category with ten replications) were introduced in to the separate
plastic containers (1 L capacity) and allowed to feed on known 5 g quantity
of groundnut leaves treated with water extracts of IC, PM and AV. Three containers
were similarly set up, but without larvae in order to estimate the leaf dessication
factor. The weight gain was assessed till the pre-pupation for every 24 h on
fresh containers i.e., after subtraction of the leaf dessication factor. The
unfed leaves and feacal pellets were separated each day, oven-dried and the
percentage dry weight conversion value was established. From these observations,
growth indices such as Consumption Index (CI) Relative Growth Rate (RGR) Approximate
Digestibility (AD) and Efficiency of Conversion Ingested (ECI) and digested
food (ECD) were calculated. After 24 h treatment 10 larvae from each treatment
were removed then the midgut of larvae was dissected out in the normal cold
saline. The undigested plant materials present in the gut was removed and the
midgut portion was separated, homogenized and pooled in the cold citrate phosphate
buffer (pH 7.6). After that ten percentage of the homogenate in 0.25 M sucrose
was centrifuged for 20 m at 900 g and the resulting supernatant was employed
as enzyme source (Eguchi et al., 1972; Pathak
and Sharma, 1996). Amylase and invertase activity was determined (Ishaaya
and Swirski, 1970) using 3, 5-dinitro salicylic acid and sucrose as substrates.
The lipase activity was evaluated following the method of Sadasivam
and Manickam (1997). In all cases the activity of the enzyme was expressed
on the protein basis (Finney, 1971).
RESULTS AND DISCUSSION
Crude extracts of the tested plants interfered with the normal development
and metamorphosis of S. litura, which was manifested at different stages
of the life cycle. The majority of the treated nymphal instars were died, either
after an extended larval period or after pupation, indicating that the bioactive
components of the leaf extracts persisted for a long time in the insects
body and did not get metabolized fully during the larval stage or larval pupal
moult (Gebreyesus and Chapya, 1983). The effect of the
plant extracts on S. litura closely resembled the effects of juvenile
hormone (JH) on insect larvae, naturally a prolongation of normal instars and
adult periods (Srivastava et al., 1965;
Sahayaraj and Agnul, 2004; Martin
and Gobalakrishnan, 2005).
|| Biological and morphological features of S. litura
after IC, PA and AV treatments (No. of larvae 50)
|**Indicates oral application
|| Nutritional indices of S. litura larvae after AI,
CG, PP and VN treatments
|**Indicate oral application
Among the three plant extracts of I. carnea and A. vasicata
had prolonged nymphal and adults followed by P. murex. The most of the
periods oral application also been appeared to be prolonged duration both the
larval and pupal periods. The extract treated larvae showed various types of
deformities and high levels of mortality. The dead nymphs and adults were invariably
connected with moulted skin. Of these, experimental plant extract, P. murex
shows two more days additionally taken for fifth nymphal instars to adult stage
followed by A. vasicata and I. carnea. Similarly the nymphal adult
intermediaries and adult deformities were also maximum observed under the experiment
with P. murex (Table 1).
At several stages shown in the extended larval period, growth and development sustained, but in several occurrence the larvae became larger than normal fifth instar nymphs and they were eventually died. From this work clearly articulated the plant extract therefore, seems to have a suppressive action on the moulting process through the metabolic activity, which allowed the treated larvae to live without moulting at few days. In this aspect, the three plant extract, bear a resemblance to the action of excess juvenile hormone, which also hampered with moulting process. Since, this result showed statistically significant for invertase (except the P. murex) but not for lipase activity (Table 2). Meanwhile, complete or partial moulting takes place during the time of metamorphosis nymphal instars to adult it might be due to the interference of plant extracts.
The nymphal and adult intermediaries also deformities were higher with when
the botanicals were administered orally. Adult longevity was higher in contact
toxicity test (except in the control and AV treatment) followed by the dermal
and contact toxicity tests respectively. However, there was no significant differences
were observed between the treatments of three plant extracts. Duncan Multiple
Range Test (DMRT) demonstrated that all the extracts investigated showed significant
difference at 5% level within the treatments, as far as the pupation (except
IC and AV) nymphal-adults intermediate (except PM and nymphal deformity (except
AV) and adult deformity were concerned among the treatment of plants tested
in this experiment. The formation of intermediates may be due to the direct
action of the plant extracts through their stimulation of the corpora allata
to produce an increased amounts of JH which was sufficient to maintain nymphal
characters in the posterior part of the body but insufficient to prevent the
pre-adult stage present at the anterior part. Consequently moulting was disrupted
and larval, pupal intermediate was produced. Ambika-Devi
and Mohandas (1982) and Koul et al. (1996)
also been reported that plant extracts has antifeedent and growth inhibitory
activities on economically affected series pests under various fields.
Here, this study observed enzyme activities such as amylase and invertase
was lower after treatment with following plant extracts I. carnea, P.
murex and A. vascica. Among the four experimental plants Protease
activity was very low in P. murex then A. vasicata, finally C.
gigantia treatments (Table 3). In similarity to this experiment
explained amylase and invertase, lipase activity was decreased compared with
control categories. Of these three application method tested oral application
strongly reduced both amylase and invertase activity, followed by topical and
contact applications. Likewise the similar patterns were observed with all four
experimental extracts. But in the case of P. murex treatment lipase activity
was enhanced by the oral applications. In both the control and A. vasica
treatment lipase activity was higher in the contact application followed by
the oral and dermal application respectively. However, the data were statistically
significant at 5% level. Ethanol extracts of Aesculus hippocastanum L.
showed toxic effect against Thaumetopoae solitaria (Frey.) larvae (Erturk,
2006). These results suggest that there may be different compounds in extracts
possessing different bioactivities, particularly antifeedant and toxicity of
insect pests. We can conclude that this study suggest that water extracts of
I. carnea, P. murex and A. vasica plants belonging to families
taxonomically possesses toxic principles with significant antifeedant effects
and could be a potential crop protectants against S. litura. These kinds
of similar observations have been already found out through the other medicinal
plants having solvent based extracts.
||Digestive enzyme profile of S. litura larvae after
IC, PM AV treatments. Values expressed in parentheses indicates per cent
reduction or (*) increased activity
|*O: Oral application, D: Dermal application and C: Contact
application. Means followed by the same letter are not significantly different
at 5% level
It is interesting that certain plant extracts employed in the present study
possess antifeedence and toxicity in the lepidopteran pest species studied (Jacobson,
1989; Selvaraj et al., 2005; Ahmad
et al., 2009). It appears that these plants contain different chemicals
that act upon target cells effectively (Aswad et al.,
2003; Sadek and Anderson, 2007). Though the chemical
analysis of the active plants is underway and we hope to reveal some interesting
similarities between the chemicals isolated as well as their bioactive compounds
from the medicinal plants (Murugan et al., 1999;
Bell et al., 1990; Sahayaraj, 1998). The
activity of these extracts also suggests a future exploitation of the materials
in to potential insect management chemicals with a minimum environmental impact.
It is advantageous, as the extracts at higher doses act as antifeedant, while
the lower dilution of the same plant is oral toxicant (Sedek
and Anderson, 2007). The results implying the dual role of a single plant
material in caster and groundnut pest management by chosen plant extracts. It
also suggests that by a single application of these compounds a complete success
of the insect control can be achieved.
Digestive enzymes play a major role in insect physiology by converting complex
food materials into micro molecules necessary to provide energy and metabolites
for growth, development and other vital functions (Eturk,
2006). The results of this study indicate that three is considerable variation
in midgut amylase, invertase and protease activity between the insects treated
with the different plant extracts. The present results were agreed with another
one pest experiment on digestive enzymes such as protease activity in gut contents
and tissue was significantly reduced after precocene treatment to Acheae
janata (Linn.) (Mathews and Muraleedharan, 1992).
However the study demonstrated the increased protease activity after plant extract
treatments. The increased activity of midgut lipase all the plant extract treatments
might account for a greater utilization of exogenous lipids and resulting in
the bio-mass production (Champagne et al., 1992;
Babu et al., 1997; Desai
and Desai, 2000; Ahmad et al., 2006). They
concluded that I. carnea treatment decreased the level of lipids probably
suggesting the depletion of the reserviour of the fats in Atractomorpha crenulata
(Fab.). When S. litura larvae of that were injected with azadiractin
(1 mg g-1) suffered reduced amylase and invertase activity and lower
digestibility (Ayyangar and Rao, 1989; Senthil
et al., 2006) as well as this study also explained the digestibility
differs widely in relation to the food given to an insect. However, they reported
that dermal application of precocene II significantly reduced the level of enzyme
activity of A. janata.
In the present study, we observed that botanical extract treatment decreases the nymphal instars and adult emergence, food consumption and conversion but increases the nymphal instars and adult emergence. Plant compounds interrupted the secretion of digestive enzymes and further led to the disruption of gut physiology. Moreover, feeding is necessary for the stimulation of digestive enzyme activities and might have interfered in enzyme substrate complex and affect the peristaltic movement of the gut, a phenomena which was very clear in the alteration of faecal pellet production by the botanicals treatment. Oral administration of botanical extracts ended to have more impact on growth and development, feeding and digestive processes also relative to dermal and contact treatments. Thus the present study strongly proved to be indicated that the possible use of these plant extracts for the control of series caster and vegetable crop pest of S. litura.
Authors would like to sincere thanks Rev. Fr. Premkumar (M.S.W) Secretary and Correspondent in Malankara Catholic College, Mariagiri for valuable suggestions, insightful advices and a boost of in my scientific endeavors. Corresponding author would like to express the sincere thanks for Mr. S. Muthukumar (Research Scholar in CPRC, St. Xaviers College, (Autonomus), Palayamkottai for his support and suggestion for this manuscript preparation.
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