Comparative Bio-Efficacy of Aqueous Extracts of <i>Loncarpous cyanescens</i> and <i>Trema orientalis</i> Against Flea Beetle (<i>Podagrica</i> Spp) (Coleoptera: Chrysomelidae) Infestation And Yeild of Okra

Abstract

In Nigeria, Okra ( Abelmoschus esculentus ) is attacked by two flea beetle species, Podagrica uniforma (Jaq.) and Nisotra dilecta (Jaq.) (Coleoptera: Chrysomelidae) which are responsible for heavy defoliation and causes significant yield losses and synthetic insecticides with its attendant problems is currently be employed for insect pest control. A field experiment was conducted at the Teaching and Research Farms of Rufus Giwa Polytechnic, Owo, Ondo State between June – August, 2013, to investigate the insecticidal potentials of Loncarpous cyanescens and Trema orientalis against flea beetle infestation on okra in Randomised Completely Block Design (RCBD) and treatments replicate three times. Synthetic insecticide ( Lambda cyhalothrin ) was used as check to compare the effectiveness of the plant extracts. Crude aqueous extracts of each plant was prepared by pounding 1 kg of plant leaves using mortar and pestle and soaked in 4 litres of cold water for 24 hours, sieved using muslin cloth. Spraying of okra plants were carried out at 5 spraying regimes beginning from crop establishment (4 weeks after planting (WAP) to harvesting period (50 days after planting (DAP) at weekly intervals using Knapsack 15 L sprayer under fairly calm weather condition. To assess the effect of the plant extracts and on the flea beetles; variables assessed included number of beetles were counted a day before treatment application, number of beetles post application of treatment and number of fresh fruit, fruit length and weight on 5 randomly selected plants per plot. Data collected were subjected to analysis of variance (ANOVA) and treatment means were separated using Least Significant Difference at 5% probability level. Results obtained shows that at 40 and 50 DAP i.e. at 4 th and 5 th spraying regimes, plot sprayed with L. cyanescens and T. orientalis extracts caused significant beetles infestation suppression (P 0.05) compared to synthetic insecticide control plots. In light of the foregoing, it is evident from the study that the plant evaluated possess insecticidal properties which could be exploited as bio-insecticide as alternative to synthetic insecticide in the control of Podagrica uniforma (Jaq.) and Nisotra dilecta (Jaq.) infestation under organic okra production.