88. Biologically Active Plant
Extracts Against Euproctis Fraterna
M.S.Nalina Sundari
Department of Zoology, University of Madras,
Chennai 600 025
Pesticides have the potential for contaminating
the environment and they have resulted in many complex problems.
The development of resistance by insect pests and the pollution
caused by the pesticides call for the discovery of less hazardous
alternatives. A new approach which has captured world wide attention
is the use of plant products to control pest populations. In India,
limited studies have been made to identify plants whose extracts
possess juvenile hormone like activity on insects. Studies in
this field led to the discovery of three different plants namely,
Catharanthus roseus, Datura metel and Eucalyptus globulus
the extracts of which showed promising juvenile hormone effects.
Materials and methods
The plant parts were thoroughly dried
at room temperature in shade and were then pulverized in a grinder.
25g of dried and powdered material was extracted in Soxhlet apparatus
using acetone as the solvent for 8 hours at 55oC. Different
concentrations of the plant extracts of known weight were prepared
in distilled water after dissolving the weighed amount of the
extract in acetone. Distilled water with 1 ml of acetone forms
the control solution. Newly moulted third instar larvae were separated
into different containers and were fed ad libitum with
castor leaves soaked in different concentrations of plant extracts.
They were maintained in the same concentrations till pupation.
The percentage of juvenile hormone activity of plant extracts
were then calculated using the formula adopted by Williams and
Slama (1966) and Bransly Williams (1971).
Results
The manifestations of the morphogenetic activity of juvenile hormone in insects are to maintain immaturity, promote supernumerary moulting, prevent normal pupation and produce larval-pupal or pupal-adult intermediates. The plant extracts produced various morphological deformities in E. fraterna. Depending on the doses used, the extracts affected larval and pupal development. Based on the morphological deformities, the following categories were recognised; supernumerary larvae, larval pupal intermediates, deformed pupae, pupal adult intermediates and adultoids.
Application of the extract of C.roseus leaves showed greater JH like activity while the activity was only 30.0%, 33.2% and 28.8% by the extracts of flowers, seeds and roots of C.roseus. More number of supernumerary larvae were produced in the extract of C.roseus leaves treated insects than other plant extracts tested.
The extracts of D. metel have insecticidal and antifeedant properties, but it showed only a little JH like activity. However, in case of D. metel flower extracts, 50.0% of JH activity was obtained at the concentration of 1200 ppm. Supernumerary larvae were also obtained when treated with flower extracts.
The extracts of E. globulus also
showed promising Juvenomimetic activities. 63.2% of JH activity
was obtained at the concentration of 1000 ppm of E. globulus
leaves extract. However, the extract of E. globulus seeds
showed only insecticidal properties rather than juvenile hormone
like properties, when we increase the concentration above 700
ppm. mortality was more pronounced than juvenile hormone like
activities.
Table 1 : Juvenomimetic activity of
the extracts of C.roseus on E.fraterna
| Part of plant | Concentration of | Number of insects falling in rates of | JH Activity | ||||||||
| used | the extract (ppm) | 0 | 1 | 2 | 3 | 4 | 5 | (%) | |||
|
Leaf |
400
600 800 1000 | 11
17 3 0 | 21
3 2 3 | 10
2 0 5 | 4
7 9 3 | 2
15 21 17 | 2
6 16 22 | 28.4
47.2 73.6 80.0 | |||
| Flower | 400
600 800 1000 | 30
15 7 9 | 9
16 13 3 | 7
9 4 2 | 3
3 5 5 | 1
3 11 20 | 0
4 10 11 | 14.4
30.0 52.0 62.8 | |||
| Seed | 200
400 600 800 | 27
21 19 12 | 11
11 10 7 | 5
8 5 4 | 2
6 4 5 | 4
2 9 18 | 1
2 3 4 | 19.2
25.2 33.2 48.8 | |||
| Root | 400
600 800 1000 | 26
23 15 10 | 10
9 7 5 | 8
4 4 12 | 2
4 4 12 | 3
7 12 15 | 1
3 7 8 | 19.6
28.8 44.8 56.4 | |||
Table 2: Juvenomimetic activities of
the extracts of the D.metel on E.fraterna
| Part of plant | Concentration of | Number of insects falling in rates of | JH Activity | ||||||||
| used | the extract (ppm) | 0 | 1 | 2 | 3 | 4 | 5 | (%) | |||
| Flower | 800 | 19 | 4 | 6 | 12 | 6 | 3 | 36.4 | |||
| 1000 | 7 | 11 | 12 | 16 | 2 | 2 | 40.4 | ||||
| 1200 | 6 | 9 | 4 | 21 | 5 | 5 | 50.0 | ||||
| 1400 | 3 | 8 | 4 | 25 | 6 | 4 | 54.0 | ||||
Discussion
Most of the plant extracts tested produced morphological deformities in E. fraterna and those deformities were very similar to those caused by the action of JH analogues. The extract of C.roseus showed distinct juvenile hormone like activity of E. fraterna. The extracts of flowers of D. metal showed varying degrees of juvenomimetic activities on E. fraterna. The presence of juvenile hormone like activity in the extracts from plants such as C.roseus, E. globulus, C. aurantium, D. regia etc., provides as has been pointed out by Deshpande et al. (1974) & Chokalingam and Nalina Sundari (1988), additional support to the possibility of insect plant interactions in the course of evolution. They also pointed out that subsequent production of certain secondary metabolites by these plants can influence various physiological processes in insects resulting in growth inhibition or general toxicity.
The degree of juvenile characters retained by supernumerary larvae and pupae of E. fraterna was found to be dependent on the dosages of the extracts applied. In all the plant extracts, the juvenomimetic effect showed a proportional increase with the increase in dosage up to a certain level only. Beyond that level mortality was more pronounced than the juvenomimetic effect. Secondary metabolites accumulated in the woody parts of the plant also known to exhibit JH activity (Prabhu et al. 1973).
Hence, from the present study, it is clear
that we can successfully use plant products in the control of
insect pests. They have considerable advantages over chemical
pesticides, which have residual action and hazardous effects on
non target organisms, and to which the insects have developed
resistance. The striking features of these biocides are biodegradability,
feasibility of low cost production, and amenability to genetic
engineering approaches for amplification of production. Therefore,
they show promise as potential insecticides as alternative to
chemical larvicides.
Table 3: Juvenomimetic activities of
the extracts of E.globulus on E.fraterna
| Part of plant | Concentration of | Number of insects falling in rates of | JH Activity | ||||||||
| used | the extract (ppm) | 0 | 1 | 2 | 3 | 4 | 5 | (%) | |||
| Leaf | 400
600 800 1000 | 33
23 9 5 | 8
10 19 8 | 7
6 11 2 | 2
7 6 7 | 0
4 2 15 | 0
0 3 13 | 11.2
23.6 32.8 63.2 | |||
| Flower | 1600
1800 2000 2200 | 21
4 3 5 | 11
7 3 6 | 7
9 10 6 | 9
26 27 21 | 2
2 4 7 | 0
2 3 6 | 20.4
48.4 54.0 55.2 | |||
| Seed | 200
400 600 700 | 35
29 14 12 | 10
11 10 9 | 2
6 4 5 | 2
3 19 21 | 1
1 3 2 | 0
0 0 1 | 9.6
17.6 34.8 38.0 | |||
| Root | 1400
1600 1800 2000 | 18
17 8 7 | 15
14 21 8 | 4
5 13 0 | 11
10 4 7 | 2
3 2 18 | 0
1 2 10 | 25.6
28.4 30.8 60.4 | |||
Acknowledgement
My grateful thanks are due to Dr. Jayapaul
Azariah, Professor and Head, Department of Zoology, University
of Madras, for providing facilities. I am also grateful to UGC
for Research Associateship.
References
Bransly Williams, W.R. (1971) :
Juvenile hormone activity of ethyl farnesoate dihydrochloride
with the cotton stainer Dysdercus cardinals Gerst. Bull. ent.
Res., 61 : 41-47.
Chockalingam, S & M.S.Nalina
Sundari (1988) : Juvenomimetic activities of some plant extracts
on the lepidopteran pest, Porthesia scintillans. Geobios,
15(4) : 183-184.
Deshpande, R.S., P.R.Adhikary &
H.P.Tipris (1974) : Juvenile hormone like activity of some Indian
herbaceous plants. Indian J.Exp.Biol., 12 : 572-575.
Prabhu, V.K.K., M.John & B.Ambika
(1973) : Juvenile hormone activity in some South Indian plants.
Curr. Sci., 42 : 725-726.
Williams, C.M. & K.Slama (1966)
: The Juvenile hormone III. Effect of the "Paper factor"
on the growth and metamorphosis of the bug. Pyrrhocoris apterus.
Biol. Bull., 130(2) : 247-253.
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