Efficacy of <i>Lippia javanica</i> leaf powder and <i>Combretum imberbe</i> wood ash against the larger grain borer ( <i>Prostephanus truncatus</i> ) in stored maize

Prostephanus truncatus is a major storage pest responsible for substantial maize grain losses. This study evaluated the efficacy of Lippia javanica leaf powder and Combretum imberbe wood ash in controlling P. truncatus in stored maize. The study consisted of two separate trials, each with six treatments, replicated thrice and arranged in a Completely Randomized Design (CRD). The treatments for the first trial consisted of four dosages of L. javanica (2, 4, 6, 8 g) applied to 200 g of maize grain, the untreated control and Actellic Gold Dust. The second trial treatments consisted of four dosages of C. imberbe (2, 4, 6, 8 g) applied to 200 g of maize grain, an untreated control and Actellic Gold Dust. Each experimental unit was infested with 10 adult Prostephanus truncatus, and assessments were conducted at 7, 14, and 21 days after treatment. The efficacy of L. javanica leaf powder and C. imberbe in the control of P. truncatus was assessed by determining insect mortality, insect reproduction, mean grain weight loss, and mean grain damage. Both biopesticides significantly (p < 0.05) increased adult insect mortality and suppressed reproduction compared to the untreated control. The highest mortality (90%) was observed at 8 g for both botanicals and reproduction was reduced by 5–85% relative to the control for L. javanica and 10–92% for C. imberbe, depending on dosage. The findings demonstrate that L. javanica and C. imberbe are promising bioinsecticides for maize protection against P. truncatusa especially for smallholder farmers.