FORMULATION OF RICE HUSK - BASED INSECTICIDAL DUSTS FOR THE CONTROL OF CALLOSOBRUCHUS MACULATUS (FABRICIUS) AND SITOPHILUS ZEAMAIS (MOTSCHULSKY)

Abstract

Rice Husk (RH) is one of the agricultural wastes causing environmental pollution in Nigeria. Thus, recycling them to useful materials becomes matter of importance. This study therefore evaluated the biotoxic effects of ash of rice husk against infestation by Callosobruchus maculatus and Sitophilus zeamais. The Research was carried out in the Laboratory, Department of Crop, Soil and Pest Management, The Federal University of Technology, Akure, Nigeria under prevailing laboratory conditions at temperature 28 ± 2oC and relative humidity 75 ± 5%. For toxicity evaluation, uninfested Ife-brown cowpea variety and SUWAN-1-yellow maize variety were treated with ashes at 0.2, 0.4, 0.6, 0.8 and 1.0 g/20 g of seeds respectively and untreated seeds were set as control. The mortality was observed at 24, 48, and 72 h for cowpea and at 24, 48, 72 and 96 h for maize. The oviposition, F1 adult emergence, grain damage and weight loss as well as percentage inhibition and percentage Weevil Perforation Index were determined. Each treatment was replicated three times. The most effective Rice Husk Ash was used to make formulations with different plant powder and the best formulation was used to test for long term protection of the seeds. The linear regression analysis showed that there was significant correlation between insect mortality and oviposition as well as between adult emergence and seed weight loss. Jemila Rice Husk Ash (JRHA) was formulated separately with Eugenia aromatica, Piper guineense, Xylopia aethiopica, Zingiber officinale and Ocimum gratissimum powder at ratio 50:50. These mixtures were tested for their effectiveness against cowpea beetle and maize weevil. JRHA + E. aromatic powder was found most effective against the two insects. The long-term protectability effects of the formulation was evaluated by treating the grains at 0.2, 0.4, 0.6, 0.8 and 1.0 g/200 g and grouped into four seed lots. Grains without treatment were set as negative controls while those treated with 0.01g pirimiphos methyl were used as positive controls. Jute bags and hessian sacks were used to store the protected commodities for the periods of observation. The results obtained showed that the survival of the insects depend on the dosage of the mixture and period of exposure. At twenty four months of protection there were reduction in mortality of insect treated with pirimiphos methyl when compared to others. Furthermore, both jute bag and hessian sack used for storage of treated cowpea and maize seeds appeared to be good storage materials but jute bag appeared better as a storage material as it was able to hold plant powders firmly for a long time than the hessian sacks due to high mortality recorded on both insects in jute bag than hessian sack. The formulation did not adversely affect the germination of the protected seeds. The JRHA + E. aromatica formulation significantly inhibited the activities of Acetycholinesterase (ACHE), Carboxyl esterase (CarEST), Glutathione S-Transferase (GST), Superoxide Dismutase (SOD), Catalase (CAT), Glutathione-Peroxidase (GPx), Amylase (AMY), Protease (PRO) and Lipase (LPS) activities in the treated C. maculatus and S. zeamais. However, for effective control of C. maculatus and S. zeamais JRHA + E. aromatic formulation is recommended using jute bag as storage materials.