Arinafril A., Rahmawati, C., Kirana, A., & Salsabila, S. (2025). Population and Mortality of Plutella xylostella Pests on Cabbage Leaves Treated with Monosodium Glutamate and Botanical Insecticide of Neem Extract. In: Herlinda S et al. (Eds.), Prosiding Seminar Nasional Lahan Suboptimal ke-13 Tahun 2025, Palembang 20 Oktober 2025. (pp. x–y). Palembang: Penerbit & Percetakan Universitas Sriwijaya (UNSRI).Cabbage (Brassica oleracea var. capitata L.) is one of the important horticultural commodities that is highly susceptible to Plutella xylostella infestation, which can significantly reduce crop yield. This study aimed to evaluate the effectiveness of a mixture of monosodium glutamate (MSG) and neem extract in suppressing the population and increasing the mortality of P. xylostella on cabbage plants. The research was conducted from April to September 2024 at the Thai Nguyen University of Agriculture and Forestry (TUAF) using a Randomized Block Design (RBD), with grouping criteria based on the uniformity of environmental conditions, including light intensity, temperature, and soil humidity, to minimize environmental variation effects on observations. The experiment consisted of six treatments: E+MSG 0 (control), E+MSG 1 (0.1 mg), E+MSG 2 (0.2 mg), E+MSG 3 (0.3 mg), E+MSG 4 (0.4 mg), and E+MSG 5 (0.5 mg), each replicated five times. Data were analyzed using inferential statistics to determine the effect of treatments on pest population and mortality. The results showed that in the control treatment, the average P. xylostella population reached 35 individuals per plot with approximately 29 individuals in mortality, while the E+MSG 1 and E+MSG 2 treatments were the most effective, reducing the population to 3 and 11 individuals, respectively, with higher mortality rates than other treatments. Therefore, the combination of MSG and neem extract has the potential to serve as an environmentally friendly pest control alternative, reducing dependency on synthetic chemical insecticides.