Efficacy of aqueous leaf extracts of negro coffee (<i>Cassia occidentalis</i>) and lemon grass (<i>Cymbopogon citratus</i>) in the management of nematode pests of okra (<i>Abelmoschus esculentus</i> l. Moench)

Abstract

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 and 100 %, where 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 (42.28 mg/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.

Keywords: Nematodes Phytochemical, screening Infra-red spectrum, Secondary metabolites