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Title: Evaluation of Insecticidal and Repellent Properties of Lantana Camara L. and Tephrosia Vogelii Hook Against the Maize Grain Weevil Sitophillus Zeamais Motschulsky, in Maize Grain Storage in Kenya
Authors: Ogendo, Joshua Ondura
Keywords: Insecticidal and Repellent Properties -- Lantana Camara L. -- Tephrosia Vogelii Hook -- Maize Grain Weevil -- Maize Grain Storage
Issue Date: Nov-2000
Publisher: Egerton University
Abstract: A study was conducted to evaluate the insecticidal and repellent properties of two local plants, Lantana camara L. (Verbenaceae) and Tephrosia vogelii Hook (Fabaceae) against the maize grain weevil, Sitophilus zeamais Motschulsky ((loleoptera: Curculionidae), in maize grain storage in Kenya. This was preceded by a farmer survey Whose primary objectives were to confirm the pest status of S. zeamais, assess the potential and identity of local plant species with insecticidal or repellency against insect pests of stored grains and generate recommendations for the laboratory based in-depth investigation. The maize weevil was confirmed as the most important insect pest of maize in storage and two plants, Lantana camara L. and Tephrosia vogelii Hook identified and recommended for laboratory evaluations at Egerton University, Kenya. Laboratory bioassays and quality evaluations were conducted to determine the efficacy and repellency of the two plant materials against S. zeamais and their effects on the grain quality. The study was also expected to generate recommendations for adaptive research. Three (1.0, 2.5 and 5.0% w/w) and five (1.0, 2.5, 5.0, 7.5 and 10.0% w/w) rates ofthe ground powders of each plant material were used for the grain quality evaluation and laboratory bioassay experiments, respectively. An untreated (control) and synthetic insecticide, Actellic super 2% dust at 0.05% (W/w) were included for comparison in all experiments. The treatments were arranged in a completely randomised design (CRD) with six and four replicates for the grain quality evaluation and laboratory bioassays, respectively. All the experiments were conducted under ambient conditions of temperature, relative humidity and l2-hr light: 12-hr dark regime. Results showed that the ground powders were slow acting but effective in controlling adult S. zeamais causing 83-90 and 85-94% mortality for L. camara and T. vogelii, respectively, over a 21-day exposure period. The lethal mean exposure times (LT5o) to achieve 50% mortality varied from 5-6 days (7.5-10.0% w/w) to 7.5-8 days (2.5- 5.0%w/W) for both plant materials. The probit regression lines showed significant relationship between weevil mortality and the powder concentration. The powders and insecticide were equally effective in reducing the number of adult Fl insects by 275% compared to the untreated control. The botanical treatments and synthetic insecticide were equally effective in reducing (by 25%) insect damage on stored maize grains but the level of damage was independent of the amount of plant powder applied. The two plant materials showed significantly higher repellency against S. zeamais compared to Actellic super and the untreated control. However, T. vogelii at 7.5 and l0% w/w were the most repellent (87.5%) followed by T. vogelii at 2.5% w/w and L. camara at 10% w/w with 65 and 62.5%, respectively. The powders significantly minimised the magnitude of depression in grain moisture content over the 5 months storage period but no significant efi'ect on the percent germination of stored maize grains was detected. The magnitude of depression of grain MC was less with higher dosages of the plant powders. The powders of both plants at 5% w/w had significantly different grain MC from that of the untreated control. Grain colour and odour were unaffected by the plant powders during the 5 months of grain storage. The two test plants have insecticidal and repellent properties, which if properly harnessed, can be effective in the protection of grains in storage. The plant option appears viable, cost-effective and sustainable if the recommendations are tailored to meet the specific user domains, varying levels of pest attack and toxicity requirements.
Appears in Collections:Faculty of Agriculture

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