Introduction: The global population is rapidly approaching 9.7 billion by 2050, with Africa and Asia playing significant roles in this growth. This surge necessitates increased crop production, highlighting the importance of effective pest control to ensure food security. India, facing an annual crop loss of about 30% due to pests and diseases, emphasizes the urgency of maintaining ecological balance in natural ecosystems. The diamond back moth (Plutella xylostella L.) poses a substantial threat to cruciferous plants globally, causing severe yield losses of 50–80% in infested cabbage. Addressing this challenge is crucial for minimizing crop losses and securing successful harvests. Our study aimed to analyze the emergence and abundance of small, medium, and large-sized larvae before and after applying treatments. Materials and Methods: A study with five treatments, including Nirgundi-chakramardha biopesticide and a control (Cypermethrin), was conducted. Each treatment was replicated four times, and the entire experiment was set up using a randomized block design. Results: After chemical application, all treatments displayed significant differences. The biopesticide in our study produced notable results within trial groups. Notably, the control group exhibited excellent results compared to the other treatments. Conclusion: The Nirgundi-chakramardha Biopesticide exhibited insecticidal activity against Diamondback moth pests, specifically targeting medium-sized larvae. Although not statistically significant compared to the control group, its efficacy in pest control, especially during the larval stage, indicates its potential as a viable pest management option. Further research and optimization could improve its effectiveness in combating Diamondback moth infestations.