Madras Agric. J. 92 (4-6) : 308-310 April-June 2005

Studies on the repellant properties of Calotropis gigantea R. Br. plant parts against important storage insect pests R. ARULPRAKASH AND R. VEERAVEL Dept. of Agricultural Entomology, Tamil Nadu Agrl. University, Coimbatore - 641003, Tamil Nadu.

Abstract : Repellant activity of the milkweed plant, Calotropis gigantea R.Br. was evaluated against important storage pests such as Callosobruchus maculatus (Fab.), Sitophilus oryzae Linn, and Tribolium castaneum (Herbst). Leaf, flower, stem, root and whole plant were Soxhlet extracted by using petroleum ether solvent and repellency test was carried out using glass olfactometer. Whole plant extract at 5 per cent concentration had maximum repellent effect followed by leaf, flower, stem and root extracts. Keywords: Milkweed plant, plant part powders, storage insect pests, repellency.

Introduction Biopesticides obtained from plant sources are safer, devoid of residue problems and almost negligible application risks as compared to synthetic chemical pesticides (Banerji et al., 1985). Calotropis gigantea R.Br. (Family: Asclepiadaceae) grows profusely with a wide distribution in India and the world over. It is known to have insecticidal (Solunke and Deshpande, 1991), antifeedant (Pari et al. 1998) and nematicidal properties (Philip et al. 1993). Stored grains were damaged by various species of insect pests among which the most important pests were pulse beetle, Callosobruchus maculatus (Fab.) (Pereira, 1983), rice weevil, Sitophilus oryzae Linn. (Koura and El Halfway, 1967) and the red flour beetle, Tribolium castaneum (Herbst) (Malek, et al. 1996).

Test insects such as C. maculatus, S. oryzae and T. castaneum were reared in cowpea, maize and wheat flour respectively. A glass olfactometer was used to find the repellent properties of the plant extracts against T. castaneum. The olfactometer consisted of a middle glass chamber (60 mm diameter) from which six equally spaced tubes (20 cm length and 2.5 cm diameter) project outwards. The middle chamber had an opening of 2.5 cm diameter. The distal end of each arm was attached with a glass beaker (7 cm diameter and 9 cm height). Seeds such as cowpea, maize and groundnut were taken for conducting experiments for C. maculatus, S. oryzae and T. castaneum respectively.

Materials and Methods Fresh C. gigantea whole plants were collected and they were shade dried for three months. Leaf, flower, stem and roots were separated, soxhlet extracted (using petroleum ether (bp-60°C) solvent and different concentrations (1 to 5%) were prepared separately. Whole plant extract was prepared by mixing equal

Five grams of above said seeds were dipped in different concentrations (1 to 5 per cent) of Soxhlet extracts of C. gigantea plant parts for 15 min separately and air-dried for 10 min. After air drying, treated seeds were placed in the arms of olfactometer and five days old sixty above said insects were released. In control, seeds were dipped in water. Each

proportion of leaf, flower, stem and root extracts.

Studies on the repellant properties of Calotropis gigantea R. Br. plant parts against important storage insect ...

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Table 1. Impact of C. gigantea plant extracts on the orientation behaviour of test insects Test Insects

Plant parts used for extraction

1

2

3

4

5

Control

- 0.6957 - 0.6098

- 0.7727 - 0.6500

- 0.8140 - 0.7368

- 0.8571 - 0.7838

- 0.9024 - 0.8333

0.02 0.01

- 0.5789 - 0.4857

- 0.6210 - 0.5294

- 0.6667 - 0.5758

- 0.7143 - 0.6250

- 0.7647 - 0.7333

0.04 0.02

Whole plant

- 0.7647

- 0.8000

- 0.8750

- 0.9565

-1.0000

0.01

Leaf Flower

- 0.7391 - 0.6667

- 0.7778 - 0.7073

-0.8182 - 0.7500

- 0.8605 - 0.7949

- 0.9048 - 0.8421

0.05 0.02

Stem Root

- 0.5787 - 0.5000

- 0.6216 - 0.5429

- 0.6667 - 0.5882

- 0.7143 - 0.6875

- 0.7647 - 0.7419

0.03 0.01

Whole plant

- 0.7500

- 0.7872

- 0.8261

- 0.9091

- 0.9535

0.02

Leaf Flower

- 0.5455 -0.4359

-0.6585 -0.5263

-0.7436 -0.6000

-0.8378 -0.7500

-0.9429 -0.8667

-0.03 -0.04

- 0.3143 - 0.2571

-0.4375 -0.4194

-0.4839 -0.4667

-0.6429 -0.6296

-0.7692 -0.7600

-0.05 -0.01

- 0.6250

-0.7333

-0.8140

-0.9024

-1.0000

-0.02

Leaf Flower C.maculatus Stem Root

S.oryzae

EPI values (%) at concentrations

T.castaneum Stem Root Whole plant EPI = Excess Proportion Index

Values are the mean of four replications

treatment was replicated four times. The repellant property of the C. gigantea was tested by choice test. After three hours, the number of beetles present in each concentration were recorded. From the values obtained the repellency was observed and defined in terms of Excess Proportion Index (EPI) according to Sakuma and Fukami (1985). EPI defined as follows. NS-NC EPI = -------------NS+NC Where, NS = Number of insets in the sample side and NC = Number of insets in the control side

EPI values were ranged from +1 to -1. These terms simply express polarity of the directional choice. Positive and negative values indicate positive and negative approaches respectively. Results and Discussion Results of the experiment were summarized in the Table 1. Which showed that All the test insects viz., C. maculatus, S. oryzae and T. castaneum avoided feeding on cowpea, maize and groundnut seeds treated with Soxhlet extracts of C. gigantea leaf, flower, stem, root and whole plant. The results clearly indicated

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that 5 per cent concentration of C. gigantea whole plant extract was the most effective repellant for the above said test insects followed by leaf, flower, stem and root extracts. The EPI values for all the C. gigantea plant part extracts (except control) used in this study showed negative values. Sahayaraj and Paulraj (2000) found similar results with neem, Vitex negundo, Allium cepa and C. gigantea plant extracts. Summary Soxhlet extracts of C. gigantea plant parts was found to possess repellent properties. All the plant part extracts repelled the test insects such as C. maculatus, S. oryzae and T. castaneum. Among the extracts whole plant extract had maximum repellant effect followed by leaf, flower, stem and root extracts. References Banerji, R., Gopal Misra, Nigani, S. K., Prasad, N., Pandey, R. S. and Mathur, Y.K. (1985). Indigenous plants as antifeedant. Indian J. Ent., 44: 71-76. Koura, A. and EI - Halfway, M. (1967). Studies on the susceptibility of certain Egyptian varieties of maize, Zea mays, to infestation with rice weevil and lesser grain borer and the preference to these insects. Agri. Res. Hev. Cairo, 45: 490-495.

R. Arulprakash and R. Veeravel

Malek, M.A., Praveen, B. and Talunder, D. (1996). Insecticidal properties of four indigenous plant extracts against adults of CR-1 Strain of Tribolium castaneum (Herbst). Bangladesh J. Ent., 6: 7-11. Pari, K., Rao, P.J., Devakumar, C. and Rastogi, J.N. (1998). A novel insect antifeedant nonprotein amino acid from Calotropis gigantea. J. Natl. Prod., 61: 102-104. Pereira, J. (1983). The effectiveness of six vegetable oils as protectants of cowpea and Bambara groundnuts against infestation by Callosobruchus maculatus (F.). J. Stored Product Res., 19: 57-62. Philip, T., Govindaiah, Bajpai, A.K. and Datta, R.K. (1993). Effect of certain leaf extracts on hatching and mortality of the root knot nematode, Meloidogyne incognita, infesting mulberry. Ind. J. Sericulture, 32: 37-47. Sahayaraj, K. and Paulraj, M.G. (2000). Impact of some plant products on the behaviour of Tribolium castaneum H. in groundnut seed. Intl. Arach. Newsl. (IAN), 20: 7576. Sakuma, M. and Fukami, H. (1985). The linear track olfactometer an assay device for taxes of the German cockroach, Blatella germanica (Linn) toward their aggregation pheromone. Appl. Ent. Zool, 4: 523 - 525. Solunke, B.R. and Deshpande, S.V. (1991). Studies on use of plant products for control of lemon butterfly larvae. J. Maharashtra Ag. Univ., 16: 302-303.

(Received : June 2005; Revised : October 2005)