Impact of Neem Seed, Neem Leaf Extract, Insecticide, and Baking Soda on the Population and Damage of Fall Armyworm on the Growth and Yield of Maize (Zea Mays) in Njala Lowland

Abstract

The fall armyworm (FAW), Spodoptera frugiperda, poses a significant threat to maize production in Sierra Leone and across sub-Saharan Africa, necessitating the development of effective and sustainable control strategies. A field study was conducted at Njala University, to evaluate the efficacy of neem leaf extract, neem seed powder, a synthetic insecticide, and baking soda solution, and their impact on the growth and yield of three maize varieties (DMR-ESR-Yellow, Samma 252, and PVR SYN9). The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. Treatments included neem leaf extract, neem seed powder, a synthetic insecticide (standard control), baking soda solution, and an untreated control. Data were collected on vegetative growth parameters (plant height, stem girth, leaf area), pest incidence (number of insects, percentage damage, percentage incidence), and yield components. The results demonstrated that all treatments significantly suppressed FAW infestation and damage compared to the untreated control, with their efficacy becoming more pronounced over time. At 8 WAP, neem leaf, baking soda, and the synthetic insecticide were the most effective, completely eliminating insect populations and disease incidence. Neem leaf extract consistently promoted superior vegetative growth, resulting in the tallest plants and largest leaf area. Furthermore, neem leaf application significantly enhanced yield components, producing the largest cob size (22.56 cm), heaviest cobs (44.41 g), and highest 1000-seed weight (98.80 g), outperforming all other treatments. Among the varieties, PVR SYN9 exhibited the highest level of resistance to FAW and the greatest yield potential, recording the highest total number of seeds per cob (3800.0). The study concludes that neem leaf extract is a highly effective botanical pesticide, serving as a viable and sustainable alternative to synthetic insecticides for managing fall armyworm in maize. Its integration with a resistant variety like PVR SYN9 is recommended for optimizing vegetative growth, minimizing pest damage, and maximizing grain yield in smallholder farming systems in Sierra Leone.