Repellent Properties of Microencapsulated Rosemary Essential Oil Against the Indian Meal Moth (Plodia interpunctella)

Background: The search for natural and eco-safe alternatives to synthetic insecticides has intensified due to increasing concerns over chemical residues and resistance development in stored-product pests. The Indian meal moth (Plodia interpunctella) is considered one of the most destructive pests of stored foods. Rosemary essential oil (REO) possesses strong repellent activity; However, its practical application is limited by the rapid evaporation of its active components, particularly 1,8-cineole. Objective: This study aims to enhance the long-term repellency of REO against P. interpunctella by employing microencapsulation technology to slow and control the release of its volatile compounds. Methods: Microcapsules containing REO were produced via spray-drying using Arabic gum as the polymeric wall material. Encapsulation efficiency (expected between 70–90%), particle morphology, and structural characteristics were examined. A dual-choice bioassay was used to compare the repellency of free oil and microencapsulated oil. The persistence of repellency was monitored over 0, 3, 7, 14, and 21 days. Results: Both formulations demonstrated strong initial repellency (RI > 80% on day 0). However, the microencapsulated preparation retained significantly higher repellency over time, maintaining RI values above 65% for up to 14 days, whereas the free oil showed a sharp decline within 3–7 days. Conclusion: The improved performance of the microcapsules is attributed to controlled release provided by the polymeric wall, which reduces the voltage of active constituents. Microencapsulated REO represents a promising sustainable alternative for long-term protection of stored food products and can be incorporated into active packaging systems.