Evaluation of aqueous extracts of five plants in the control of flea beetles on okra (Abelmoschus esculentus (L.) Moench)

Thesis Overview

<p> INTRODUCTION&nbsp;</p><p>Okra [Abelmoschus esculentus (L.) Moench.] is the most important fruit vegetable crop and a source of calorie (4550 kcal/kg) for human consumption. It ranks first before other vegetable crops (Babatunde et al., 2007). Okra is an important vegetable in West Africa, India, Brazil and the United states (Kemble et al., 1995). In Nigeria, okra is one of the most important vegetables in terms of consumption and production area (Iremiren and Okiy, 1986). Okra occupies about 1.5 million hectares of the arable land in Nigeria alone (IFA,1992). The World production of common okra as fresh fruit vegetable is estimated at 1.7 million t/year (Schippers, 2000). Okra is rich in vitamins, calcium, potassium and other mineral matters. Its fruits can be cooked in a variety of ways. It can be fried in butter or oil and cooked with necessary ingredients (Yadav et al., 2001). Okra mucilage is suitable for medicinal and industrial applications. It has been medically found that its application serves as a plasma replacement or blood volume expander. Industrially, okra mucilage is usually used to glace certain papers and also useful in confectionery among other uses (Markose and Peter, 1990). However, the yield of okra has been reported to be very low in Nigeria, hardly up to 7t/ha (Schippers, 2000). Among the problems of okra production in Nigeria are insect pest infestations, disease incidence and poor soil nutrient level. Egwuatu (1982) reported that Podagrica uniforma, Jacoby and P. sjostedti Jacoby (Coleoptera: Chrysomelidae) are the most destructive insect species of okra at Nsukka, Nigeria. Emosairue and Ukaegbu (1994) in a study of insects associated with okra showed that the flea beetles, P. uniforma and P. sjostedti, are the most prevalent and most serious insect pests of okra in the Calabar humid area of Nigeria. The two flea beetles are important vectors of okra mosaic virus (OMV), a tymovirus. In Nigeria, okra is heavily infected by this virus if grown without controlling for the flea beetles (Lana and Taylor, 1976). The effectiveness of various synthetic organic insecticides has been reported in the control of flea beetles in particular as well as other pests of okra. Adenuga (1971), revealed thaT&nbsp; MATERIALS AND METHODS Field trials were conducted during the cropping seasons of 2007 and 2008 at the Teaching and Research Farm, Adeyemi College of Education, Ondo (Latitude 07º 05’N, Longitude 04º 50’E, 27.5 m) in the rain forest zone of Nigeria. The site for the experiment measuring 17 m ×25 m (425 m2 ) which had been previously cultivated was cleared and marked out into plot sizes of 3 x 4 m and separated by a 1-m pathway. The experiment was laid out in a Randomized Complete Block Design (RCBD) with five treatments and four replicates. The planting material, an early maturing cultivar of okra (NHAE 47-4), was procured from the Ondo State Agricultural Development Project, Ondo, Nigeria. The okra seeds were dibbled at a spacing of 60 cm between rows and 30 cm between plants. The five plant materials that were used in the trials included: goat weed (Ageratum conyzoides L.), physic nut (Jatropha curcas L.), siam weed (Chromolaena odorata L.), bitter leaf (Vernonia amygdalina L.) and Sweetsop (Annona squamosa Linn.). These botanicals, in addition with the synthetic insecticide, lambda-cyhalothrin and the control represented the seven treatments that were executed in the experiment. The experimental plot was kept weed free throughout the period of the trial. Fertilizer (N.P.K.) was incorporated into the soil at the rate of 200kg/ha. Selection and collection of plant species The selection of plants used in the study was based on previously reported insecticidal properties of the plants against many insect pests of vegetables. The plants, with the exception of Annona spp., which was collected within Ondo town, were all collected from the main campus, Adeyemi College of Education, Ondo. The plant parts were plucked by hand and put in a jute bag ready for extraction. Preparation of aqueous extract The plant parts were washed to remove sand, dust and chemical contaminants, shade-dried for 5-6 days on a clean concrete platform and then powdered using wooden pestle and mortar. The extracts of the botanicals were prepared following the method of Rezaul Karim et al. (1992). Each of the five plants extracts was prepared at a concentration of 10% w/v by weighing 450 g of the powder and then soaked in plastic bucket containing 3.5 litre of warm water (600 C). The resulting solution was stirred continuously for 10 minutes and left to stand for 12 hrs. Filtration of the plant extracts was done shortly before application in the field using muslin cloth. The final volume of each plant extract filtrate was made up by diluting with 1 litre of distilled water. The stickiness and adherence of each of the plant extract was enhanced by the addition of 100 ml of 5 % soap solution as surfactant. Spraying of the plant extracts was done early in the morning before sunrise because of the photodegradable nature of the extracts. Data collection and <br></p>