Efficacy of extracts of Tithonia diversifolia (Hemsl) A. Gray as protectant against maize weevil (Sitophilus zeamais [Motsch.]) and cowpea weevil, Callosobruchus maculatus F. on stored grains

Abstract

This study sought to determine the efficacy of Tithonia diversifolia (African Sunflower) as pesticides against maize weevil Sitophilus zeamais and bean beetle Callosobruchus maculatus. The research was conducted to ascertain the toxicity potency of T. diversifolia on insects’ mortality, repellency, adult emergence, seed damage and weight loss for the treatment of stored products and determine their minimum effective dosage for application. T. diversifolia collected from the premises of Kwara State University, Malete were air-dried, grinded and dissolved in 50 g to 600 ml of four different extracts (Ethanol, Methanol, n-Hexane and aqueous). S. zeamais and C. maculatus were reared in the laboratory at 60-75% relative humidity and 25-35 oC. After the whole extraction, ten unsexed S. zeamais and C. maculatus were infested in 10 g of grains and replicated three times in each application of extracts with different treatment levels. The mortality and other parameters were counted post-treatment. The mean results of the parameters studied were significantly different at (P< 0.05). N-hexane extracts was most toxic to S. zeamais while Methanol extract was most toxic to C. maculatus. Thus, all the extracts were potent, and they reduced insects’ oviposition, increased mortality, improved repellence, inhibited reproduction, grain damage and weight loss in storage compared to the untreated control. Subjected to the qualitative phytochemical screening, active compounds discovered to be present in T. diversifolia include tannin, flavonoid, saponin, phenol, terpenoid, glucosides and alkaloid. The study proffers the use of T. diversifolia, a readily available, safe and ecofriendly botanical for farmers as short and long-term storage of the stored products.