Efficacy of Aqueous Leaf Extracts of Negro Coffee (Cassia occidentalis) and Lemon Grass (Cymbopogon citratus)in the Management of Nematode Pests of Okra (Abelmoschus esculentus L. Moench)

A two-year rain-fed field trials to evaluate the efficacy of aqueous leaf extracts of Cassia occidentalis and Cymbopogon citratus at different levels in the management of nematode pests of okra was conducted. The levels of treatments used were 25%, 50%, 75%, 100% while 0% served as control. The experimental design was a randomized complete block design (RCBD). Effects of treatments on growth, yield, soil nematode population, root weight and root gall indices were determined. Phytochemical screening and infra-red spectrum to determine the secondary metabolites in the leaf extracts were also carried out. It was observed that the treated plants especially those that received 50% level and above performed significantly better (p=0.05) than the control with respect to the measured parameters. The phytochemical result revealed the presence of tannin (7.4%), crude alkaloids (2.5%), saponin (0%) and crude oxalates (42.28mg/g) in cassia while lemon grass contained tannin (4.5%), crude alkaloids (0.52%,), saponin (1.76%) and oxalates (0%). The infra-red spectrum revealed that the two plant extracts contained very strong and broad absorption bands ~3400-1cm region, assignable to ~NH stretching mode probably of alkaloid family. The medium absorption bands were due to ~CH bands which are common in natural products. The medium absorption bands are also strong indicators of other compounds in the leaf extracts. The use of botanically derived crude leaf extracts of cassia at 50% and lemon grass at 75% in the management of nematode pests of okra will therefore be of economic benefit, ensuring food security. Article History: Received : 03-06-2015 Revised : 04-09-2015 Accepted : 23-09-2015 Keywords: Nematodes Phytochemical screening Infra-red spectrum Secondary metabolites *Corresponding Author: Izuogu N.B E-mail: [email protected]@201 5 STAR Journal, Wollega University. All Rights Reserved. INTRODUCTION Okra, Abelmoschus esculentus (L) Moench is one of the most important vegetables in Nigeria. It is a tropical plant, which grows best in warm climate. It is available all year round, with a peak during summer months. Okra ranks high amongst the economical important vegetables of the world. The immature fruits of Okra, which are good sources of vitamin C, are used for the preparation of certain soups and sauces (Diouf, 1997). Successful production of okra in Nigeria has been hampered to some extent by nematode pests, especially the root- knot nematodes Meloidogyne spp. (Enopka et al., 1996; Agu and Ogbuji, 2001). According to Sikora and Fernandez (2005), root-knot nematodes are particularly damaging vegetables in tropical and subtropical countries of the world and cause losses up to 80% in heavily infested fields. Three species of root-knot nematodes, M. javanica, M. incognita and M. arenaria, are found in Nigeria and they attack over 140 species of cultivated plants amongst which are important food crops and vegetables (Enokpa et al., 1996). In the Tropics, M. incognita very frequently attack okra (Singh et al., 1993; Khan et al., 1998). Khan and khan (1994) reported that M. incognita elicited leaf browning, suppression in plant growth, fruit yield and photosynthetic pigments in okra. Nematode management is complicated and difficult and at present, chemical control is employed in many crops to maintain their populations below economic threshold levels (Eapen et al., 2005). Recently, the control of plant parasitic nematodes, using conventional nematicides has declined internationally because of the inherent toxicity of many existing synthetic pesticides to non-target organisms and their persistence in the environment. There is increasing need to find more acceptable alternatives. The potential for nematicidal activity of indigenous plants and their products has been reported by earlier workers (Adekunle and Fawole, 2003; Izuogu et al., 2009, 2010, 2011, 2012; Yakubu and Izuogu, 2013; Abolusoro et al., 2013; Olabiyi et al., 2013). The nematicidal principles of plant origin in the form of substances such as isothiocyanates, thiophenics, glucosides, alkaloids, phenolics, thianins and fatty acids have been identified (Fatoki and Fawole, 2000). There may be many more plants however, not yet tested, which could prove to be effective for the management of plant parasitic nematodes. The present study was therefore designed to investigate nematicidal potential of aqueous leaf extracts of Cassia occidentalis and Cymbopogon citratus against nematode pest of okra. Original Research 1A Peer-reviewed Official International Journal of Wollega University, Ethiopia DOI: http://dx.doi.org/10.4314/star.v4i3.00 ISSN: 2226-7522(Print) and 2305-3372 (Online) Science, Technology and Arts Research Journal Sci. Technol. Arts Res. J., July-Sep 2015, 4(3): 000-000 Journal Homepage: http://www.starjournal.org/ Efficacy of Aqueous Leaf Extracts of Negro Coffee (Cassia occidentalis) and Lemon Grass (Cymbopogon citratus)in the Management of Nematode Pests of Okra (Abelmoschus esculentus L. Moench) Izuogu N.B*, Yakubu L.B, Abolusoro S.A and NwabiaI.W. Department of Crop Protection, Faculty of Agriculture, University of Ilorin, Nigeria Abstract Article Information A two-year rain-fed field trials to evaluate the efficacy of aqueous leaf extracts of Cassia occidentalis and Cymbopogon citratus at different levels in the management of nematode pests of okra was conducted. The levels of treatments used were 25%, 50%, 75%, 100% while 0% served as control. The experimental design was a randomized complete block design (RCBD). Effects of treatments on growth, yield, soil nematode population, root weight and root gall indices were determined. Phytochemical screening and infra-red spectrum to determine the secondary metabolites in the leaf extracts were also carried out. It was observed that the treated plants especially those that received 50% level and above performed significantly better (p=0.05) than the control with respect to the measured parameters. The phytochemical result revealed the presence of tannin (7.4%), crude alkaloids (2.5%), saponin (0%) and crude oxalates (42.28mg/g) in cassia while lemon grass contained tannin (4.5%), crude alkaloids (0.52%,), saponin (1.76%) and oxalates (0%). The infra-red spectrum revealed that the two plant extracts contained very strong and broad absorption bands ~3400-1cm region, assignable to ~NH stretching mode probably of alkaloid family. The medium absorption bands were due to ~CH bands which are common in natural products. The medium absorption bands are also strong indicators of other compounds in the leaf extracts. The use of botanically derived crude leaf extracts of cassia at 50% and lemon grass at 75% in the management of nematode pests of okra will therefore be of economic benefit, ensuring food security. Article History: Received : 03-06-2015 Revised : 04-09-2015 Accepted : 23-09-2015 Keywords: Nematodes Phytochemical screening Infra-red spectrum Secondary metabolites *Corresponding Author: Izuogu N.B E-mail: [email protected]@201 5 STAR Journal, Wollega University. All Rights Reserved. INTRODUCTION Okra, Abelmoschus esculentus (L) Moench is one of the most important vegetables in Nigeria. It is a tropical plant, which grows best in warm climate. It is available all year round, with a peak during summer months. Okra ranks high amongst the economical important vegetables of the world. The immature fruits of Okra, which are good sources of vitamin C, are used for the preparation of certain soups and sauces (Diouf, 1997). Successful production of okra in Nigeria has been hampered to some extent by nematode pests, especially the root- knot nematodes Meloidogyne spp. (Enopka et al., 1996; Agu and Ogbuji, 2001). According to Sikora and Fernandez (2005), root-knot nematodes are particularly damaging vegetables in tropical and subtropical countries of the world and cause losses up to 80% in heavily infested fields. Three species of root-knot nematodes, M. javanica, M. incognita and M. arenaria, are found in Nigeria and they attack over 140 species of cultivated plants amongst which are important food crops and vegetables (Enokpa et al., 1996). In the Tropics, M. incognita very frequently attack okra (Singh et al., 1993; Khan et al., 1998). Khan and khan (1994) reported that M. incognita elicited leaf browning, suppression in plant growth, fruit yield and photosynthetic pigments in okra. Nematode management is complicated and difficult and at present, chemical control is employed in many crops to maintain their populations below economic threshold levels (Eapen et al., 2005). Recently, the control of plant parasitic nematodes, using conventional nematicides has declined internationally because of the inherent toxicity of many existing synthetic pesticides to non-target organisms and their persistence in the environment. There is increasing need to find more acceptable alternatives. The potential for nematicidal activity of indigenous plants and their products has been reported by earlier workers (Adekunle and Fawole, 2003; Izuogu et al., 2009, 2010, 2011, 2012; Yakubu and Izuogu, 2013; Abolusoro et al., 2013; Olabiyi et al., 2013). The nematicidal principles of plant origin in the form of substances such as isothiocyanates, thiophenics, glucosides, alkaloids, phenolics, thianins and fatty acids have been identified (Fatoki and Fawole, 2000). There may be many more plants however, not yet tested, which could prove to be effective for the management of plant parasitic nematodes. The present study was therefore designed to investigate nematicidal potential of aqueous leaf extracts of Cassia occidentalis and Cymbopogon citratus against nematode pest of okra. Original Research 1A Peer-reviewed Official International Journal of Wollega University, Ethiopia DOI: http://dx.doi.org/10.4314/star.v4i3.00 ISSN: 2226-7522(Print) and 2305-3372 (Online) Science, Technology and Arts Research Journal Sci. Technol. Arts Res. J., July-Sep 2015, 4(3): 000-000 Journal Homepage: http://www.starjournal.org/ Efficacy of Aqueous Leaf Extracts of Negro Coffee (Cassia occidentalis) and Lemon Grass (Cymbopogon citratus)in the Management of Nematode Pests of Okra (Abelmoschus esculentus L. Moench) Izuogu N.B*, Yakubu L.B, Abolusoro S.A and NwabiaI.W.