Journal of Agricultural Science; Vol. 16, No. 7; 2024 ISSN 1916-9752 E-ISSN 1916-9760 Published by Canadian Center of Science and Education 114 Potential of Neem (Azadirachta indica) Extract in Managing Fall Armyworm on Maize Tom Richard Okello 1 , Cosmas Wacal 1,2 , Wadria Denis Peter 1 , Allan Obonyom Tekkara 3 , Costa Gumisiriya 2 & John Patrick Kanahe Kagorora 2 1 Department of Agriculture and Natural Sciences, Faculty of Agriculture, Uganda Martyrs University, Kampala, Uganda 2 Department of Crop and Animal Production, Faculty of Agriculture and Environmental Sciences, Mountains of the Moon University, Fort Portal City, Uganda 3 Ngetta Zonal Agricultural Research Institute, National Agricultural Research Organization, Lira City, Uganda Correspondence: Cosmas Wacal, Department of Crop and Animal Production, Faculty of Agriculture and Environmental Sciences, Mountains of the Moon University, P.O. Box 837, Fort Portal City, Uganda. Tel: 256-780-633-425. E-mail: cosmas.wacal@mmu.ac.ug Received: April 6, 2024 Accepted: May 16, 2024 Online Published: June 15, 2024 doi:10.5539/jas.v16n7p114 URL: https://doi.org/10.5539/jas.v16n7p114 Abstract This research assessed the effect of neem leaf extract on the larval population of the fall armyworm and the level of damage, growth, and yield of maize. A Randomized Complete Block Design (RCBD) with four treatments (Control, 50 g per L, 100 g per L and 200 g per L of neem leaf extract) applied within the two seasons of 2022A and 2022B. The findings showed that a higher concentration (200 g per L) of neem leaf extract-treated maize plants registered the least leaf damage (0.15), severity (0.15), and larvae population (0.1). This effect was most attained during the 1 st season of maize production and at the earliest vegetative weeks of maize growth (3 WAP to 5 WAP, i.e., weeks after planting). The higher neem leaf extract concentration of 200 g per L produced the most significant (p < 0.001) effect on maize growth traits. A higher plant height (162.51 cm), longer leaf length (112.5 cm), wider leaf width (11.7 cm), and broader stem girth (11.91 cm) were attained under 200 g per L of neem leaf extract treated plots during the 1 st season of maize production and 11 WAP. The findings of this showed that a relatively high concentration of neem leaf extract produced a higher cob weight (200 g per L = 180.1 g) followed by 100 g per L (174.1 g), 50 g per L (140.9 g) and control (139 g). The weight was optimised during the 1 st season of maize production (163.8 g). The grain yield was higher under 200 g per L (153.7 g) of neem extract. The above findings demonstrated that a high concentration of neem leaf extract reduced fall armyworm infestation and increased maize plant growth and yield. Farmers should, therefore, be encouraged to apply 200 g per L of neem leaf extract in the management of fall armyworms and improve plant growth and yield because it contains antifeedant and insecticidal properties against the fall armyworm. Keywords: Azadirachtin, fall armyworm, grain yield, maize, neem leaf extract 1. Introduction Maize Zea mays L. (Poaceae) is a nutritionally important food crop with much-needed nutrients for human and animal health (Arnarson, 2019). In Uganda, maize covers an average land area of 384,000 ha with yield annually 522,000 t, with a grain yield averaging 1.3 t per ha (MAAIF, 2018). However, despite these figures, the overall trend of production per unit area/or ha and yield during this period shows stagnation or decline, with maize growth primarily attributed to the expansion of cultivated areas rather than yield per unit area (Epule et al., 2021). The current trend of maize production is held back by several problems related to abiotic stress, such as erratic rainfall, poor/degraded soil quality, and biotic stress, such as pests and diseases contributing to poor yield (FAO, 2019a). It is widely accepted that this stress will become more acute due to climate change, resulting in a potential loss of up to 10% in maize production across Africa and Latin America by 2055 (Jones & Thornton, 2003). Among the biotic stressors, the fall armyworm Spodoptera frugiperda (FAW) (J.E. Smith) (Lepidoptera: Noctuidae) emerges as the more serious, attacking maize plants at all stages of growth, from seedling, vegetative,