Role of Combined Ash and Terbuphos as Preplanting Corm Treatment to Manage Corm Borer Weevils (Cosmopolites sordidus) on Plantains and Stimulate Growth

The banana borer weevil, Cosmopolites sordidus is the most important pest that causes significant damage to banana and plantain in Cameroon. Most farmers in Buea Sub-Division, South West Region, Cameroon, believe that applying a combination of Terbuphos (Counter 10G®) and Wood Ash (from rubber plants) as seed treatments helps to protect suckers from the banana weevil and stimulate plant growth better than their sole forms. The main objective of this research was to evaluate the efficacy of a bio-stimulant botanical pesticide (i.e., combined wood ash and oil palm bunch residue ash) and a conventional synthetic insecticide (Terbufos) applied as seed treatment to manage C. sordidus and stimulate the growth of plantains. Laboratory and field experiments (complete randomized blocks) were carried out at the research station of IRAD Ekona, Southwest Cameroon. The experimental setup comprised the following treatments; 5 g Wood Ash/5 g Terbuphos, 10 g Wood Ash/10 g Terbuphos, 30 g Wood Ash/30 g Terbuphos, 20 g Wood Ash only and 20 g Terbuphos only, and the control (neither ash nor Terbuphos) replicated three times each. The results demonstrated significant treatment effects (P=0.05 and F5,54), with differences in weevil mortality, repulsion, oviposition on the surface of the corm, number of larvae inside the corm and plant growth parameters for treatments with Terbuphos compared to the control. Meanwhile, ash treatments did not show any mortality effect on insects. However, Wood Ash showed non-mortality effects in the laboratory as compared to the control, although it was not significantly different (P=.05 and F5,54). 20 g Terbuphos only, followed by the combination of 5 g Wood Ash and 5 g Terbuphos per 1 L of water had the most effective results in enhancing growth parameters and survival of the plants (Percentage Coefficient of Infestation of 30.2 and 65.6 as compared to the 97.9 for the control).