The Insecticidal Effects of <i>Pogostemon cablin</i> Against Coconut Leaf Beetle, <i>Brontispa longissima</i>

The coconut leaf beetle (<i>Brontispa longissima</i>) is a destructive pest in Malaysia, significantly impacting coconut plantations and leading to economic losses. While chemical pesticides are commonly used for control, their prolonged application raises concerns regarding human health risks, environmental impact, and the development of pesticide resistance. This study evaluates the insecticidal efficacy of Cypersect EC (Cypermethrin 5.5%), Neem oil (1.2% Azadirachtin), and natural biopesticides derived from <i>Pogostemon cablin</i> and <i>Clinacanthus nutans</i> leaf extracts against different developmental stages of <i>B. longissima</i> using a direct dipping method under laboratory conditions. Results indicate that Cypersect EC exhibited the highest mortality rates, significantly outperforming other treatments (P < 0.05), with increasing concentrations leading to higher mortality across all pesticide types. Among biopesticides, <i>P. cablin</i> extract demonstrated superior insecticidal activity compared to <i>C. nutans</i>, although neither achieved 100% mortality at the highest tested concentration. The study also found that <i>B. longissima</i> larvae were more susceptible to treatments than adult beetles, suggesting that early intervention could enhance control effectiveness. The mode of action analysis suggests that Cypersect EC disrupts neural function by inhibiting cholinesterase activity, whereas biopesticides likely exert toxicity through contact exposure and metabolic disruption. These findings underscore the potential of <i>P. cablin</i> as a sustainable alternative for <i>B. longissima</i> management, reducing dependence on synthetic chemicals while supporting environmentally friendly pest control strategies. Further research is recommended to optimize <i>P. cablin</i> formulations, assess its long-term field efficacy, and explore its integration into integrated pest management (IPM) programs for sustainable coconut cultivation.