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Larvicidal and repellent potential of Albizzia amara Boivin and Ocimum basilicum Linn against dengue vector, Aedes aegypti (Insecta:Diptera:Culicidae)
Bioresource Technology 98 (2007) 198–201
Short Communication
Larvicidal and repellent potential of Albizzia amara Boivin and Ocimum basilicum Linn against dengue vector, Aedes aegypti (Insecta:Diptera:Culicidae) K. Murugan ¤, P. Murugan, A. Noortheen Division of Entomology, Department of Zoology, Bharathiar University, Coimbatore 641 046, India Received 28 June 2005; received in revised form 1 December 2005; accepted 7 December 2005 Available online 10 February 2006
Abstract Investigations were made to test the larval toxicity and smoke repellent potential of Albizzia amara and Ocimum basilicum at diVerent concentration (2%, 4%, 6%, 8% and 10%) against the diVerent instar (I, II, III and IV) larvae and pupae of Aedes aegypti. The LC50 values of A. amara and O. basilicum for I instar larvae was 5.412 and 3.734, II instar 6.480 and 4.154, III instar 7.106 and 4.664, IV instar 7.515 and 5.124, respectively. The LC50 and LC90 values of pupae were 6.792%, 5.449% and 16.925%, 15.474%. The smoke toxicity of A. amara was more eVective against A. aegypti than the O. basilicum. © 2006 Elsevier Ltd. All rights reserved. Keywords: Aedes aegypti; Albizzia amara; Ocimum basilicum; Larvicidal; Pupicidal; Smoke toxicity
1. Introduction Mosquitoes are nuisance to human beings and spread dreadful disease like malaria, Wlariasis, dengue haemorrhagic fever and Japanese encephalitis etc., Aedes aegypti, the yellow fever mosquito, is also a well-known vector of dengue. Scott et al. (1993) observed that it showed more dependency on human blood rather than on other vertebrates. Moreover, the insects in general, and A. aegypti in particular, developed resistance to a variety of insecticides. These factors have created a search for biodegradable and target-speciWc insecticides for the mosquitoes. Plant products have been used by traditionally human communities in many parts of the world against the vectors and species of insects. The phyto-chemicals derived from plant sources can act as larvicides, insect growth regulators, repellents and ovipositional attractants and have deterrent activities observed by many researchers (Babu * Corresponding author. Tel.: +91 422 2422 222x483; fax: +91 422 2425 706. E-mail address: [email protected] (K. Murugan).
0960-8524/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2005.12.009
and Murugan, 1998). Repellents have an important place in protecting man from the bites in insect pests. An eVective repellent will be useful in reducing man vector contact and in the interruption of disease transmission. A repellent compound should be toxic, non-irritating and long lasting. Amides, imides, esters and other polyfunctional compounds are known to be good repellents (Kalyanasundaram and Das, 1982). Plants could be an alternative source for mosquito repellents because they constitute a potential source of bioactive chemicals and typically are free from harmful eVects (Isman, 1995). Because of this, much interest has been focused on plant extracts, or plant essential oils as potential mosquito repellent agents (Young-Cheol Yang et al., 2004). Murugan et al. (2003) studied the interactive eVect of botanicals (Neem, Pongamia) and Leucas aspera, Bacillus sphaericus against the larvae of Culex quinquefasciatus. Vahitha et al. (2002) studied the larvicidal eYcacy of Pavonia zeylanica L. and Acacia ferruginea D.C. against C. quinquefasciatus Say. Shigeo et al. (2004) reported larvicidal eVect of neem against A. aegypti and chironomid larvae. The aim of this work was to evaluate the larvicidal,
K. Murugan et al. / Bioresource Technology 98 (2007) 198–201
pupicidal and repellent potential of A. amara and O. basilicum against dengue vector, A. aegypti. 2. Methods 2.1. Plant collection and preparation of plant extracts The plants of A. amara and O. basilicum were collected locally. The green leaves were washed with tap water and shade dried at room temperature. Voucher specimens were deposited at the Department of Zoology, Bharathiar University, Coimbatore, India. The dried plant materials were powdered by an electrical blender. From each sample, 100 g of the plant material was extracted with 300 ml of methanol for 8 h in a Soxhlet apparatus (Vogel, 1978). The plant extracts were evaporated to dryness in rotary vacuum evaporator to yield 122 mg and 110 mg of dark greenish material (residue) from A. amara and O. basilicum, respectively. One gram of the each plant residue was dissolved separately in 100 ml of acetone (stock solution), considered as 1% stock solution from which diVerent concentrations; 2%, 4%, 6%, 8% and 10% were prepared. 2.2. Test for larvicidal activity (WHO, 1996) A. aegypti was used for the larvicidal and pupicidal activity. It was maintained at 27 § 2 °C, 75–85% RH, under 14L:10D photoperiod cycles. The larvae were fed with dog biscuits and yeast at 3:1 ratio. Twenty-Wve I, II, III and IV instar larvae of A. aegypti were kept in 500 ml glass beaker containing 249 ml of dechlorinated water and 1.0 ml of desired plant extract concentration. Three replicates for each concentration were set up. A control was set up with 1.0 ml of acetone in 249 ml of dechlorinated water. The control mortality was corrected by Abbott’s formula (Abbott, 1925) and LC50, LC90, regression equation and 95% conWdence limit of lower conWdence limit (LCL) and upper conWdence limit (UCL) were calculated by using probit analysis (Finney, 1971). 2.3. Smoke toxicity test A. amara and O. basilicum leaves were also used for smoke toxicity assay. The mosquito coils were prepared fol-
199
lowing method of Saini et al. (1986) with minor modiWcations by using 4 g of coconut shell, charcoal powder as burning material. All the three were thoroughly mixed with distilled water to form a semisolid paste. Mosquito coils (0.6 cm thickness) were prepared manually and shade dried. The control coils were prepared without the plant ingredient. The experiments were conducted in glass chamber measuring 140 £ 120 £ 60 cm. A window measuring 60 £ 30 cm was situated at mid bottom of one side of the chamber. Three or four day’s old blood starved hundred adult female mosquitoes, fed with sucrose solution, were released in the chamber. A belly shaven pigeon was kept tied inside the cage in immobilized condition. The experimental chamber was tightly closed. The experiment was repeated Wve times on separate days including control, using mosquitoes of same age groups. The data were pooled and average values were subsequently used for calculations. Control was maintained in two sets. One set was run with coil lacking the active ingredient of plant powder (control I) another one was a commercial coil, which was used for positive control to compare the eVectiveness of plant coils. After the experiment was over, the fed, unfed (active and dead) mosquitoes were counted. The protection given by the smoke from plant samples against the biting of A. aegypti was calculated in terms of percentage of unfed mosquitoes due to treatment. Data were analysed using analysis of variance (ANOVA) and means separated by Duncan’s multiple range tests. 3. Results and discussion The results of larvicidal and pupicidal activity of A. amara and O. basilicum are presented in Tables 1 and 2. The two plant extracts exhibited larvicidal activities to diVerent instars (I, II, III & IV) and pupa of A. aegypti. The LC50 and LC90 values of A. amara and O. basilicum for I instar larvae were 5.243%, 3.734% and 10.059%, 7.528%, II instar 6.480%, 4.154% and 12.085%, 8.292%, II instar 7.106%, 4.664% and 13.233%, 8.746%, IV instar 7.515%, 5.124% and 13.824%, 9.767%, respectively. The regression equation of A. amara and O. basilicum for I instar larvae were Y D ¡1.197 + 0.228X and Y D ¡1.26106 + 0.33772X, II instar Y D ¡1.482 + 0.229X and Y D ¡1.486 + 0.209X and
Table 1 Larvicidal activity of A. amara on diVerent instar larvae and pupa of A. aegypti Plants species
A. amara leaf extract
¤
Larval instar
Log LC50 [Log LC90]
LC50 [LC90 (%)]
Regression equation
95% ConWdence limit LCL [LC50 (LC90) (%)]
UCL [LC50 (LC90) (%)]
I II III IV Pupa
0.733 (0.127) 0.812 (1.082) 0.852 (1.122) 0.875 (1.141) 0.832 (1.285)
5.243 (10.059) 6.480 (12.085) 7.106 (13.233) 7.515 (13.824) 6.792 (16.925)
Y D¡1.197 + 0.228X Y D¡1.482 + 0.229X Y D¡1.486 + 0.209X Y D¡1.527 + 0.203X Y D¡0.859 + 0.126X
4.681 (9.901) 5.961 (11.010) 6.540 (11.924) 6.921 (12.397) 5.900 (14.175)
5.763 (12.217) 7.025 (13.619) 7.749 (15.177) 8.224 (15.977) 7.853 (22.158)
SigniWcant at P < 0.05 level.
Chi-square value 0.593¤ 1.926¤ 0.983¤ 1.550¤ 3.323¤
200
K. Murugan et al. / Bioresource Technology 98 (2007) 198–201
Table 2 Larvicidal activity of O. basilicum on diVerent instar larvae and pupa of A. aegypti Plants species
O. basilicum leaf extract
¤
Larval instar
Log LC50 [Log LC90]
LC50 [LC90 (%)]
Regression equation
I II III IV Pupa
0.572 (0.877) 0.618 (0.919) 0.669 (0.942) 0.710 (0.981) 0.736 (1.192)
3.734 (7.528) 4.154 (8.292) 4.664 (8.746) 5.124 (9.767) 5.449 (15.474)
Y D¡1.261 + 0.338X Y D¡1.286 + 0.310X Y D¡1.465 + 0.314X Y D¡1.415 + 0.276X Y D¡0.697 + 0.128X
95% ConWdence limit LCL [LC50 LC90 (%)]
UCL [LC50 LC90 (%)]
1.490 (6.057) 2.088 (6.745) 2.641 (7.087) 3.356 (8.000) 4.451 (13.052)
5.039 (11.386) 5.464 (5.464) 6.087 (13.271) 6.508 (14.359) 6.339 (20.027)
Chi-square value 11.967¤ 10.987¤ 12.841¤ 9.983¤ 1.124¤
SigniWcant at P < 0.05 level.
Table 3 Smoke toxicity eVect of A. amara and O. basilicum against A. aegypti Name of the plant material
A. amara O. basilicum A. amara + O. basilicum Control 1 Control 2
No. of mosquitoes tested
100 100 100 100 100
Fed mosquitoes 18bc 20b 16bc 71a 14c
Unfed mosquitoes Alive
Dead
48ab 51a 40c 29d 42cd
34b 29c 44a 0d 44a
Total
Percentage of unfed over control
82b 80bc 84ab 29d 86a
53ab 51ab 55a 0c –
Within column means followed by the same letter(s) are not signiWcantly diVerent at 5% level by DMRT. Control I¤ D Negative control—blank without plant material. Control II¤ D Positive control—Mortein coil.
Y D ¡1.46456 + 0.31397X and IV instar Y D ¡1.527 + 0.203X and Y D ¡1.41467 + 0.27604X, respectively. The regression equation values of pupae were Y D ¡0.85906 + 0.12648X and Y D ¡0.69672 + 0.12784X. The LC50 and LC90 values of pupae were 6.792%, 5.449% and 16.925%, 15.474%. Among the diVerent larval stage, the I instar larvae was more susceptible than the other instar larvae. The two plant extracts also showed considerable pupal mortality. The chi-square values were signiWcant at P < 0.05 level. Table 3 showed that the combination of two plant powders increased the toxicity of the smoke compared to individual plant powers. Fed and unfed mosquitoes were counted after the individual treatment of A. amara and O. basilicum and were 18 and 20 as fed, and 82 and 80 as unfed, respectively. After combined treatment of A. amara and O. basilicum, there were 16 fed and 55 unfed mosquitoes. Comparison of positive control of the combined treatment showed good smoke toxicity eVect on A. aegypti. A. amara and O. basilicum extracts showed considerable larvicidal and pupicidal properties, which could be due to the active compound acting on the mosquito larvae. The higher mortality of mosquito larvae was due to the combined action of plant compounds that might be acting on the midgut epithelial cells and exerted their toxic eVects on mosquito. An insect repellent is a chemical that acting in the vapor phase prevents an insect from reaching a target to which it would otherwise be attracted (Brown, 1977). In the present study the smoke emerged from the A. amara and O. basilicum considerably aVected the mosquito survival and pronounced high repellent potential. The chemicals such as
linalool, ocimene, borneol, methylchavicol etc., present in the O. basilicum (Chopra et al., 1982) might have interacted with A. amara and brought out smoke toxicity. Selvaraj Pandian et al. (1995) also studied powdered preparation of the leaves of Adhatoda vasica (adhatoda), Azadirachta indica (neem) and Ocimum sanctum (tulsi), which on burning with charcoal produced smoke which repelled Armigeres subalbatus and C. quinquefasciatus to prevent their biting activity for 6–8 h. In the present study the earlier larvae were most aVected after the treatment of A. amara and O. basilicum, which could be due to the age and physiological status of larvae. The active substances of O. basilicum was toxic to the younger instar larvae of A. aegypti. Thus, these products can be used as economically viable form of personal protection against mosquito vector. Moreover, this kind of plant derived product does not cause any ill-eVect to other beneWcial organism. (Murugan, 2004). Acknowledgements The authors are thankful to the Head, Department of Zoology, Bharathiar University, Coimbatore, India for the facilities provided. References Abbott, W.S., 1925. A method of computing the eVectiveness of an insecticide. J. Econ. Entomol. 18, 265–267. Babu, R., Murugan, K., 1998. Interactive eVect of neem seed kernel and neem gum extracts on the control of Culex quinquefasciatus say. Neem Newslett. 15 (2), 9–11.
K. Murugan et al. / Bioresource Technology 98 (2007) 198–201 Brown, A.W.A., 1977. Insecticide resistance in mosquitoes: pragmatic review. J. Am. Mosq. Control Assoc. 2, 123–140. Chopra, R.N., Nayar, S.L., Chopra, I.C., 1982. Indian Medicinal Plants. CSIR, New Delhi, p. 558. Finney, D.J., 1971. In: Probit Analysis. Cambridge University Press, London, pp. 68–72. Isman, M.B., 1995. Leads and prospects for the development of new botanical insecticides. Rev. Pestic. Toxicol. 3, 1–20. Kalyanasundaram, M., Das, 1982. Larvicidal synergistic activity of plant extracts for mosquito control. Indian J. Med. Res. 82, 19–23. Murugan, K., 2004. Chemical and botanical pesticides on their impact on the biological control agents on insects. In: Albanis, T.A. (Ed.), Proceedings of the 3rd European conference on pesticides and related organic micro pollutants in the environment. University of Ioannia, Greece, pp. 445–450. Murugan, K., Vahitha, R., Baruah, I., Das, S.C., 2003. Integration of botanicals and microbial pesticides for the control of Wlarial vector, Culex quinquefasciatus. Ann. Med. Entomol. 12 (1&2), 11–23. Saini, H.K., Sharma, R.M., Bami, H.L., Sidhu, K.S., 1986. Preliminary study on constituents of mosquito coil smoke. Pesticides 20, 15–18. Scott, T.W., Chow, E., Strickman, D., Kittayapong, P., Writz, R.A., Lorenz, L.H., Edman, J.D., 1993. Blood feeding pattern of Aedes aegypti (Dip-
201
tera: Culicidae) collect in a rural Thai village. J. Med. Entomol. 30, 922–927. Selvaraj Pandian, R., Manoharan, A.C., Pandian, R.S., 1995. Herbal smoke a potential repellent and adulticide for mosquitoes. Insect Environ. 1 (3), 14–15. Shigeo, K., Tenji, K., Murugan, K., 2004. Larvicidal eVects of neem (Azadirachta indica) Seed kernel extracts against Paratanyarsus grimmii (Diptera: Chironomidae) and Aedes albopictus (Diptera: Culicidae). Med. Entomol. Zool. 55 (3), 247–250. Vahitha, R., Venkatachalam, M.R., Murugan, K., Jebanesan, A., 2002. Larvicidal eYcacy of Pavonia zeylanica L. and Acacia feruginea D.C. against Culex quinquefasciatus Say. Bioresour. Technol. 82, 203–204. Vogel, A.I., 1978. In: Text Book of Practical Organic Chemistry. The English Language Book Society and Longman, London, p. 1368. WHO, 1996. Report of the WHO informal consultation on the evaluation and testing of insecticides CTD/WHO PES/IC/96.1. Geneva, Switzerland, p. 69. Yang, Y.-C., Le, E.-H., Lee, H.-S., Lee, D.-K., Ahn, Y.-J., 2004. Repellency of aromatic medicinal plant extracts and a steam distillate to Aedes aegypti. J. Am. Mosq. Control Assoc. 20 (2), 146–149.
Short Communication
Larvicidal and repellent potential of Albizzia amara Boivin and Ocimum basilicum Linn against dengue vector, Aedes aegypti (Insecta:Diptera:Culicidae) K. Murugan ¤, P. Murugan, A. Noortheen Division of Entomology, Department of Zoology, Bharathiar University, Coimbatore 641 046, India Received 28 June 2005; received in revised form 1 December 2005; accepted 7 December 2005 Available online 10 February 2006
Abstract Investigations were made to test the larval toxicity and smoke repellent potential of Albizzia amara and Ocimum basilicum at diVerent concentration (2%, 4%, 6%, 8% and 10%) against the diVerent instar (I, II, III and IV) larvae and pupae of Aedes aegypti. The LC50 values of A. amara and O. basilicum for I instar larvae was 5.412 and 3.734, II instar 6.480 and 4.154, III instar 7.106 and 4.664, IV instar 7.515 and 5.124, respectively. The LC50 and LC90 values of pupae were 6.792%, 5.449% and 16.925%, 15.474%. The smoke toxicity of A. amara was more eVective against A. aegypti than the O. basilicum. © 2006 Elsevier Ltd. All rights reserved. Keywords: Aedes aegypti; Albizzia amara; Ocimum basilicum; Larvicidal; Pupicidal; Smoke toxicity
1. Introduction Mosquitoes are nuisance to human beings and spread dreadful disease like malaria, Wlariasis, dengue haemorrhagic fever and Japanese encephalitis etc., Aedes aegypti, the yellow fever mosquito, is also a well-known vector of dengue. Scott et al. (1993) observed that it showed more dependency on human blood rather than on other vertebrates. Moreover, the insects in general, and A. aegypti in particular, developed resistance to a variety of insecticides. These factors have created a search for biodegradable and target-speciWc insecticides for the mosquitoes. Plant products have been used by traditionally human communities in many parts of the world against the vectors and species of insects. The phyto-chemicals derived from plant sources can act as larvicides, insect growth regulators, repellents and ovipositional attractants and have deterrent activities observed by many researchers (Babu * Corresponding author. Tel.: +91 422 2422 222x483; fax: +91 422 2425 706. E-mail address: [email protected] (K. Murugan).
0960-8524/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2005.12.009
and Murugan, 1998). Repellents have an important place in protecting man from the bites in insect pests. An eVective repellent will be useful in reducing man vector contact and in the interruption of disease transmission. A repellent compound should be toxic, non-irritating and long lasting. Amides, imides, esters and other polyfunctional compounds are known to be good repellents (Kalyanasundaram and Das, 1982). Plants could be an alternative source for mosquito repellents because they constitute a potential source of bioactive chemicals and typically are free from harmful eVects (Isman, 1995). Because of this, much interest has been focused on plant extracts, or plant essential oils as potential mosquito repellent agents (Young-Cheol Yang et al., 2004). Murugan et al. (2003) studied the interactive eVect of botanicals (Neem, Pongamia) and Leucas aspera, Bacillus sphaericus against the larvae of Culex quinquefasciatus. Vahitha et al. (2002) studied the larvicidal eYcacy of Pavonia zeylanica L. and Acacia ferruginea D.C. against C. quinquefasciatus Say. Shigeo et al. (2004) reported larvicidal eVect of neem against A. aegypti and chironomid larvae. The aim of this work was to evaluate the larvicidal,
K. Murugan et al. / Bioresource Technology 98 (2007) 198–201
pupicidal and repellent potential of A. amara and O. basilicum against dengue vector, A. aegypti. 2. Methods 2.1. Plant collection and preparation of plant extracts The plants of A. amara and O. basilicum were collected locally. The green leaves were washed with tap water and shade dried at room temperature. Voucher specimens were deposited at the Department of Zoology, Bharathiar University, Coimbatore, India. The dried plant materials were powdered by an electrical blender. From each sample, 100 g of the plant material was extracted with 300 ml of methanol for 8 h in a Soxhlet apparatus (Vogel, 1978). The plant extracts were evaporated to dryness in rotary vacuum evaporator to yield 122 mg and 110 mg of dark greenish material (residue) from A. amara and O. basilicum, respectively. One gram of the each plant residue was dissolved separately in 100 ml of acetone (stock solution), considered as 1% stock solution from which diVerent concentrations; 2%, 4%, 6%, 8% and 10% were prepared. 2.2. Test for larvicidal activity (WHO, 1996) A. aegypti was used for the larvicidal and pupicidal activity. It was maintained at 27 § 2 °C, 75–85% RH, under 14L:10D photoperiod cycles. The larvae were fed with dog biscuits and yeast at 3:1 ratio. Twenty-Wve I, II, III and IV instar larvae of A. aegypti were kept in 500 ml glass beaker containing 249 ml of dechlorinated water and 1.0 ml of desired plant extract concentration. Three replicates for each concentration were set up. A control was set up with 1.0 ml of acetone in 249 ml of dechlorinated water. The control mortality was corrected by Abbott’s formula (Abbott, 1925) and LC50, LC90, regression equation and 95% conWdence limit of lower conWdence limit (LCL) and upper conWdence limit (UCL) were calculated by using probit analysis (Finney, 1971). 2.3. Smoke toxicity test A. amara and O. basilicum leaves were also used for smoke toxicity assay. The mosquito coils were prepared fol-
199
lowing method of Saini et al. (1986) with minor modiWcations by using 4 g of coconut shell, charcoal powder as burning material. All the three were thoroughly mixed with distilled water to form a semisolid paste. Mosquito coils (0.6 cm thickness) were prepared manually and shade dried. The control coils were prepared without the plant ingredient. The experiments were conducted in glass chamber measuring 140 £ 120 £ 60 cm. A window measuring 60 £ 30 cm was situated at mid bottom of one side of the chamber. Three or four day’s old blood starved hundred adult female mosquitoes, fed with sucrose solution, were released in the chamber. A belly shaven pigeon was kept tied inside the cage in immobilized condition. The experimental chamber was tightly closed. The experiment was repeated Wve times on separate days including control, using mosquitoes of same age groups. The data were pooled and average values were subsequently used for calculations. Control was maintained in two sets. One set was run with coil lacking the active ingredient of plant powder (control I) another one was a commercial coil, which was used for positive control to compare the eVectiveness of plant coils. After the experiment was over, the fed, unfed (active and dead) mosquitoes were counted. The protection given by the smoke from plant samples against the biting of A. aegypti was calculated in terms of percentage of unfed mosquitoes due to treatment. Data were analysed using analysis of variance (ANOVA) and means separated by Duncan’s multiple range tests. 3. Results and discussion The results of larvicidal and pupicidal activity of A. amara and O. basilicum are presented in Tables 1 and 2. The two plant extracts exhibited larvicidal activities to diVerent instars (I, II, III & IV) and pupa of A. aegypti. The LC50 and LC90 values of A. amara and O. basilicum for I instar larvae were 5.243%, 3.734% and 10.059%, 7.528%, II instar 6.480%, 4.154% and 12.085%, 8.292%, II instar 7.106%, 4.664% and 13.233%, 8.746%, IV instar 7.515%, 5.124% and 13.824%, 9.767%, respectively. The regression equation of A. amara and O. basilicum for I instar larvae were Y D ¡1.197 + 0.228X and Y D ¡1.26106 + 0.33772X, II instar Y D ¡1.482 + 0.229X and Y D ¡1.486 + 0.209X and
Table 1 Larvicidal activity of A. amara on diVerent instar larvae and pupa of A. aegypti Plants species
A. amara leaf extract
¤
Larval instar
Log LC50 [Log LC90]
LC50 [LC90 (%)]
Regression equation
95% ConWdence limit LCL [LC50 (LC90) (%)]
UCL [LC50 (LC90) (%)]
I II III IV Pupa
0.733 (0.127) 0.812 (1.082) 0.852 (1.122) 0.875 (1.141) 0.832 (1.285)
5.243 (10.059) 6.480 (12.085) 7.106 (13.233) 7.515 (13.824) 6.792 (16.925)
Y D¡1.197 + 0.228X Y D¡1.482 + 0.229X Y D¡1.486 + 0.209X Y D¡1.527 + 0.203X Y D¡0.859 + 0.126X
4.681 (9.901) 5.961 (11.010) 6.540 (11.924) 6.921 (12.397) 5.900 (14.175)
5.763 (12.217) 7.025 (13.619) 7.749 (15.177) 8.224 (15.977) 7.853 (22.158)
SigniWcant at P < 0.05 level.
Chi-square value 0.593¤ 1.926¤ 0.983¤ 1.550¤ 3.323¤
200
K. Murugan et al. / Bioresource Technology 98 (2007) 198–201
Table 2 Larvicidal activity of O. basilicum on diVerent instar larvae and pupa of A. aegypti Plants species
O. basilicum leaf extract
¤
Larval instar
Log LC50 [Log LC90]
LC50 [LC90 (%)]
Regression equation
I II III IV Pupa
0.572 (0.877) 0.618 (0.919) 0.669 (0.942) 0.710 (0.981) 0.736 (1.192)
3.734 (7.528) 4.154 (8.292) 4.664 (8.746) 5.124 (9.767) 5.449 (15.474)
Y D¡1.261 + 0.338X Y D¡1.286 + 0.310X Y D¡1.465 + 0.314X Y D¡1.415 + 0.276X Y D¡0.697 + 0.128X
95% ConWdence limit LCL [LC50 LC90 (%)]
UCL [LC50 LC90 (%)]
1.490 (6.057) 2.088 (6.745) 2.641 (7.087) 3.356 (8.000) 4.451 (13.052)
5.039 (11.386) 5.464 (5.464) 6.087 (13.271) 6.508 (14.359) 6.339 (20.027)
Chi-square value 11.967¤ 10.987¤ 12.841¤ 9.983¤ 1.124¤
SigniWcant at P < 0.05 level.
Table 3 Smoke toxicity eVect of A. amara and O. basilicum against A. aegypti Name of the plant material
A. amara O. basilicum A. amara + O. basilicum Control 1 Control 2
No. of mosquitoes tested
100 100 100 100 100
Fed mosquitoes 18bc 20b 16bc 71a 14c
Unfed mosquitoes Alive
Dead
48ab 51a 40c 29d 42cd
34b 29c 44a 0d 44a
Total
Percentage of unfed over control
82b 80bc 84ab 29d 86a
53ab 51ab 55a 0c –
Within column means followed by the same letter(s) are not signiWcantly diVerent at 5% level by DMRT. Control I¤ D Negative control—blank without plant material. Control II¤ D Positive control—Mortein coil.
Y D ¡1.46456 + 0.31397X and IV instar Y D ¡1.527 + 0.203X and Y D ¡1.41467 + 0.27604X, respectively. The regression equation values of pupae were Y D ¡0.85906 + 0.12648X and Y D ¡0.69672 + 0.12784X. The LC50 and LC90 values of pupae were 6.792%, 5.449% and 16.925%, 15.474%. Among the diVerent larval stage, the I instar larvae was more susceptible than the other instar larvae. The two plant extracts also showed considerable pupal mortality. The chi-square values were signiWcant at P < 0.05 level. Table 3 showed that the combination of two plant powders increased the toxicity of the smoke compared to individual plant powers. Fed and unfed mosquitoes were counted after the individual treatment of A. amara and O. basilicum and were 18 and 20 as fed, and 82 and 80 as unfed, respectively. After combined treatment of A. amara and O. basilicum, there were 16 fed and 55 unfed mosquitoes. Comparison of positive control of the combined treatment showed good smoke toxicity eVect on A. aegypti. A. amara and O. basilicum extracts showed considerable larvicidal and pupicidal properties, which could be due to the active compound acting on the mosquito larvae. The higher mortality of mosquito larvae was due to the combined action of plant compounds that might be acting on the midgut epithelial cells and exerted their toxic eVects on mosquito. An insect repellent is a chemical that acting in the vapor phase prevents an insect from reaching a target to which it would otherwise be attracted (Brown, 1977). In the present study the smoke emerged from the A. amara and O. basilicum considerably aVected the mosquito survival and pronounced high repellent potential. The chemicals such as
linalool, ocimene, borneol, methylchavicol etc., present in the O. basilicum (Chopra et al., 1982) might have interacted with A. amara and brought out smoke toxicity. Selvaraj Pandian et al. (1995) also studied powdered preparation of the leaves of Adhatoda vasica (adhatoda), Azadirachta indica (neem) and Ocimum sanctum (tulsi), which on burning with charcoal produced smoke which repelled Armigeres subalbatus and C. quinquefasciatus to prevent their biting activity for 6–8 h. In the present study the earlier larvae were most aVected after the treatment of A. amara and O. basilicum, which could be due to the age and physiological status of larvae. The active substances of O. basilicum was toxic to the younger instar larvae of A. aegypti. Thus, these products can be used as economically viable form of personal protection against mosquito vector. Moreover, this kind of plant derived product does not cause any ill-eVect to other beneWcial organism. (Murugan, 2004). Acknowledgements The authors are thankful to the Head, Department of Zoology, Bharathiar University, Coimbatore, India for the facilities provided. References Abbott, W.S., 1925. A method of computing the eVectiveness of an insecticide. J. Econ. Entomol. 18, 265–267. Babu, R., Murugan, K., 1998. Interactive eVect of neem seed kernel and neem gum extracts on the control of Culex quinquefasciatus say. Neem Newslett. 15 (2), 9–11.
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