Sustainable pest control: the role of coriander as a repellent plant against Leptinotarsa decemlineata say in eggplant cultivation

The study focuses on the potential repellent properties of coriander (Coriandrum sativum L.) against the Colorado potato beetle (Leptinotarsa decemlineata Say, CPB) when co-cultivated with eggplant (Solanum melongena L.). The growth stages of both plants and their relationship to beetle populations were examined. Stage I (Flowering period) and Stage II (Fruit development period) of coriander were shown to have a significant positive influence on reducing the beetle population. Furthermore, a positive correlation was observed between the adult CPB population and Stages I and II of eggplant growth, which are characterised by an increase in flower and fruit numbers when co-planted with coriander. Conversely, a negative correlation was observed between the beetle population and Stages II and III (Fruit maturation period) of eggplant growth in control plots (eggplant-only cultivation). Findings from 2018 and 2021 reinforced the repellent efficacy of coriander, showing a reduction in beetle populations during the coriander flowering, green fruit, and mature fruit stages. These findings indicate that the flowering stage of coriander coincides with the lowest adult beetle densities, suggesting that this phenological phase represents the most effective period for repellent cropping. Future studies should explore the potential role of coriander essential oils in enhancing this effect. This study contributes to the growing body of knowledge on natural pest management strategies.