BIO-EFFICACY OF PROMISING BOTANICALS AGAINST INSECT INFESTING COWPEA. CV. CO 4

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1 Indian J. Agric. Res., 40 (4) : , 2006 BIO-EFFICACY OF PROMISING BOTANICALS AGAINST INSECT INFESTING COWPEA. CV. CO 4 J. Renugadevi, N. Natarajan, R. Rajasekaran and P. Srimathi Department of Seed Science and Technology, Tamil Nadu Agricultural University, Coimbatore , India ABSTRACT Studies were carried out to evaluate the efficacy of botanicals on seed deterioration and bruchid infestation in cowpea cv. Co 4. The seeds were dry dressed with leaf powders of neem (Azadiracta indica) and soapnut (Sapindus emarginatus) (@ 10 and 20 g kg -1 of seed), rhizome powders of turmeric (Curcuma longa) and vasambu (Acorus calamus) (@ 5 and 10 g kg -1 of seed) and evaluated along with Deltamethrin and control revealed that rhizome powders of Acorus 10 g kg -1 and leaf powder of Sapindus 20 g kg -1 could control both bruchid infestation and seed deterioration rate recording 94 per cent germination after four months of storage with nil percentage of insect infestation. INTRODUCTION Quality seed is the basic input in crop production as this helps in maintaining required plant population per unit area and there by enhance the productivity of the crop. As seeds are highly valuable, more emphasis has to given for quality maintenance by adoption of proper seed management technique during storage. The proteinacious pulses seeds suffer a lot due to natural seed deterioration and attack by biotic organisms during storage. Among them, the pulse beetle Callosobruchus maculatus, which is a field carry over storage pest, is considered as the most serious pest that hastens the deteriorating rate of seed during storage. Its damage to the seed is estimated to an extent of per cent in different pulse crops (Parasail et al., 1989). Management techniques over the control of bruchids with synthetic insecticides from farm to storage and thereafter are widely recommended (Malarkodi, 2003) but this treatment due to their toxic residues restrict the use of this economic crop as feed or food. As a eco-friendly and dual purpose treatment, plant products are widely used (Mohan, 1993) for seed treatment. Hence, with the objective of evolving eco-friendly dual purpose seed treatment for cowpea, studies were made to evolve plant products against the control of storage pest and seed quality deterioration with cowpea cv. Co 4. MATERIAL AND METHODS Freshly harvested cowpea seeds of cv. Co 4 with a germination percentage of 96 per cent were collected from the central farm, TNAU, Coimbatore and sun dried to a moisture content of nine per cent, after grading with 10/64 round perforated sieve for uniformity. The seeds were dry dressed with dry leaf powders and rhizome powders in two different doses. The efficacy of the botanical treatments were also programmed to compare with deltamethrin and control. The overall treatmental details were as below: - Control (without any treatment) - Turmeric rhizome 5 g kg -1 of seed - Turmeric rhizome 10 g kg -1 of seed - Neem leaf 10 g kg -1 of seed - Neem leaf 20 g kg -1 of seed - Vasambu rhizome 5 g kg -1 of seed - Vasambu rhizome 10 g kg -1 of seed - Soapnut leaf 10 g kg -1 of seed - Soapnut leaf 20 g kg -1 of seed - Deltamethrin mg kg -1 of seed After seed treatment, the seeds were packed in gunny bags in three replications, and stored under the ambient conditions of Coimbatore (33±2 0 C and 55per cent RH) for a period of 4 months. Immediately after treatment and at monthly intervals, seeds were

2 Vol. 40, No. 4, evaluated for seed quality parameters like seed germination percentage (ISTA, 1999), seedling length, seed moisture content (ISTA, 1999) and natural insect infestation percentage (Mohan, 1993). The data gathered were statistically scrutinized as per Panse and Sukhatme (1985) for understanding the level of significance. RESULTS AND DISCUSSION All the seed treatments including deltamethrin were found to be effective in maintaining the quality of seed and in controlling the bruchid infestation. All the botanical treatments except turmeric rhizome powder preventing the bruchid infestation to totality (0 per cent) where the later recorded 23 per cent infestation after four months of storage. Schmidt et al. (1991) revealed that compounds of vasambu rhizome powder induce sickness or weakness, inhibit growth, reduce the reproductive efficiency and bring about premature death of insects. Vasambu also said to have sterilizing effect on the insect, as well as toxic towards the deposited eggs. The efficacy of turmeric rhizome powder was also supported by Vadivelu et al. (1985) and Rouf et al. (1996) as it contains the active component turmerone and arturmerone that act as repellent and antioxidant. In the present study seed treatments not only with botanicals but also with deltamethirn prevented the bruchid infestation completely upto 4 months of storage, which might be due to oviposition inhibitory properties of the botanicals and deltamethrin. Treatments with neem leaf powder also reduced the bruchid infestation to 0 per cent as it contains the inhibiting terpenoid and an active oviposition deterrent. (Buraimoh et al., 2000 and Elhag 2000). The evaluated vigour parameters viz., seedling root length, shoot length and vigour index also observed similar results, where the parameters were directly related to seed germination and indirectly related to insect infestation. The botanical seed treatment also maintained the moisture content at low level. (Table 1). The lesser moisture content could have preserved the physiological seed quality parameters, like germination of seeds, as revealed by Vishnurammethi (1996) in cowpea and Nakka et al. (1999) in soybean. The untreated seeds which expressed a drastic reduction in seed germination with advances in storage period as reported by Srimathi et al. (2001) in cowpea. Among the treatments, vasambu rhizome 10 g kg -1 maintained the germination at higher level (94 per cent) which was at par with lower dose of 5 g kg -1 of seed. The same level of germination was also maintained by soapnut leaf 20 g kg -1 (Table 1). The better performance of the above said treatments may be due to their insecticidal and antioxidant property which might have reduced the insect infestation and seed deterioration during storage. Subramanian (1949) and Pandey et al. (1976) also reported the efficacy of vasambu rhizome powder in maintaining the viability of seeds during storage. Vasambu rhizome powder is said to have an active principle β asarone, which prevented the bruchid infestation and maintained the viability of seeds. (Schmidt et al., 1991). Better seedling length in this treatment might also be due to low moisture absorption and this rhizome powder promotes seed quality preservation. But neem leaf powder treatment reduced the germinability of seeds to 20 per cent after 4 months of storage even though the activity was totally arrested. Thus the results of the present study convincingly proved that the cowpea seeds treated with vasambu rhizome 10 g kg -1 and soapnut leaf 20 g kg -1

3 264 INDIAN JOURNAL OF AGRICULTURAL RESEARCH Table 1. Influence of botanical seed treatment during storage on Moisture content, Germination and Root length of cowpea cv. Co4 Treatments Storage period in months (P) Moisture content (per cent) Germination (per cent) Root length (cm) P 0 Mean Control (16.95) (17.26) (17.46) (17.66) (17.76) (17.46) (78.43) (69.77) (63.45) (34.21) (39.00) (58.27) Turmeric rhizome 5 g kg (16.95) (17.26) (17.46) (17.56) (17.56) (17.36) (78.43) (73.54) (69.77) (58.05) (55.57) (65.43) Turmeric rhizome 10 g kg (16.95) (17.15) (17.46) (17.46) (17.56) (17.36) (78.43) (73.54) (69.77) (60.68) (60.68) (68.06) Neem leaf 10 g kg (16.95) (17.15) (17.46) (17.46) (17.56) (17.36) (78.43) (69.77) (58.27) (48.00) (35.00) (55.55) Neem leaf 20 g kg (16.95) (17.26) (17.36) (17.36) (17.46) (17.26) (78.43) (66.45) (53.00) (39.00) (26.00) (34.21) Vasambu rhizome 5 g kg (16.95) (17.36) (17.36) (17.46) (17.46) (17.36) (78.43) (78.43) (73.54) (75.02) (75.02) (75.81) Vasambu rhizome 10 g kg (16.95) (17.05) (17.05) (17.26) (17.46) (17.15) (78.43) (78.43) (78.72) (75.02) (75.02) (75.81) Soapnut leaf 10 g kg (16.95) (17.05) (17.15) (17.36) (17.66) (17.26) (78.43) (78.43) (73.54) (69.77) (66.54) (72.15) Soapnut leaf 20 g kg (16.95) (17.15) (17.36) (17.46) (17.56) (17.26) (78.43) (78.43) (73.54) (75.02) (75.02) (75.81) Deltamethrin mg kg (16.95) (17.15) (17.36) (17.46) (17.46) (17.26) (78.43) (73.54) (69.77) (66.45) (63.45) (69.77) CD (P =0.05) T P T x P T P T x P T P T x P (Figures in parentheses indicate arc sine transformed values).

4 Vol. 40, No. 4, Table 2. Influence of botanical seed treatment during storage on shoot length and vigour index of cowpea cv. Co4 Treatments Storage period in months (P) Shoot length (cm) Vigour index P 0 Mean Control Turmeric rhizome 5 g kg Turmeric rhizome 10 g kg Neem leaf 10 g kg Neem leaf 20 g kg Vasambu rhizome 5 g kg Vasambu rhizome 10 g kg Soapnut leaf 10 g kg Soapnut leaf 20 g kg Deltamethrin mg kg CD (P=0.05) T P T x P T P T x P - 508

5 266 INDIAN JOURNAL OF AGRICULTURAL RESEARCH recorded minimum seed deterioration and maintained the vigour and germination of seeds at higher levels. The next best treatments were deltamethrin and turmeric rhizome powder, recording 88 per cent and 86 per cent germination after 4 months of storage with nil bruchid infestation, while the control seeds recorded 100 per cent insect infestation with 40 per cent germination. Moreover vasambu rhizomes are available locally at lower cost while the seed treatment cost works out to only Rs. 3 / kg of seed. This treatment also found to be eco-friendly in addition to its dual-purpose economic utility of the seed for other purpose on reduction in germination of seed below Minimum Seed Certification Standard level of seed certification (75 per cent). Hence cowpea seeds could be stored under ambient condition with nil per cent insect infestation and 94per cent germination by simple dry treatment either with vasambu rhizome 5 or 10 g kg -1 of seed or soapnut leaf 20 g kg -1 of seed. REFERENCES Buraimoh, G.L. et al. (2000). Global J. Pure Applied Sci, 5: Elhag, E.A. (2000). Intel. J. Pest Mgmt., 46: ISTA (1999). Seed Sci. and Technol. Supplement Rules, 27: Malarkodi, K. (2003). Ph.D. Thesis, TNAU, Coimbatore. Mohan, S. (1993). Pestology, 20: 27. Nakka, A.K. et al. (1999). Seed Res., 26: Pandey, N.D. et al. (1976). Indian J. Ent., 38: Panse and Sukhatme (1985). Statistical Methods for Agricultural Works. I.C.A.R. Pub., New Delhi. Parasail, S.K. et al. (1989). Bull. Grain. Technol., 27: Rouf, F.M.A. et al. (1996). Bangladesh J. Entomol., 6: Schmidt, G.H. et al. (1991). J. Stored Product Res., 27: Srimathi, P. et al. (2001). Madras Agric. J., 88: Subramanian, T.V. (1949). J. Bombay Nat. Hist. Soc., 48: Vadivelu, K.K. et al. (1985). Seed Res., 13: Vishnurammethi, R. (1996). M.Sc. (Ag.) Thesis, TNAU, Coimbatore.