Nanotechnology has become a driving force in several sectors, particularly in improving plant disease control and agricultural practices. It is predicted that the integration of nanotechnology into research will revolutionise the management of post-harvest losses in horticultural crops. The emergence of resistant fungal strains due to the overuse of artificial antifungals highlights the need for alternative solutions. Harnessing the natural antifungal properties of plant essential oils (EOs) encapsulated in environmentally friendly nanosystems shows promise in addressing this challenge. The aim of this study was to evaluate the efficacy of encapsulating EOs extracted from fenugreek (Trigonella foenum-graecum) and coriander (Coriandrum sativum) within copper oxide nanoparticles (CuO-NPs) against Colletotrichum nymphaeae. The study showed that the EOs derived from fenugreek and coriander plants significantly inhibited the growth of C. nymphaeae mycelium. This inhibition was observed at concentrations of 600 and 900 ppm after 3 and 6 days of incubation. CuO-NPs effectively inhibited the growth of C. nymphaeae mycelium at various concentrations over different incubation periods, with the highest inhibition (approximately 99.9 %) observed at 900 ppm after six days. Encapsulation of these EOs in CuO-NPs showed synergistic effects against C. nymphaeae, achieving over 90 % inhibition of mycelial growth. Furthermore, the use of CuO-NPs encapsulated EOs resulted in a significant reduction in mycelial growth at different concentrations and time points. When fenugreek EOs were encapsulated with CuO-NPs, they had a stronger impact on the growth of C. nymphaeae mycelium compared to coriander EO. This impact was discernible across concentrations ranging from 90 to 900 ppm. Over an incubation period spanning 3, 6, 9, and 12 days, the inhibitory effects were observed to be 100 %, 100 %, 95.6 %, and 96.7 %, respectively. This study highlights the potential of encapsulated EOs as effective antifungal agents for pathogen control, offering practical solutions for disease management in agriculture.