COMPARATIVE EFFICACY OF AZADIRACHTIN-BASED FORMULATION IN MANAGING MEALYBUG (Nipaecoccus nipae Maskell) INFESTATION IN OIL PALM (Elaeis guineensis Jacq.)

Abstract

Mealybug (Nipaecoccus nipae) has recently emerged as a major pest in oil palm (Elaeis guineensis Jacq.) plantations in Southeast Asia, particularly in Sabah, Malaysia, where outbreaks have been associated with severe sooty mould development, impaired photosynthesis, and yield decline. Sustainable alternatives to synthetic insecticides are urgently needed to mitigate resistance development and environmental risks. This study evaluated the efficacy of an azadirachtin-based formulation combined with a plant-derived extract against N. nipae under laboratory and field conditions. Laboratory bioassays compared untreated control, azadirachtin alone, plant extract alone, and the formulation, DBMARK 30 EC with mortality assessed up to 96 h after treatment. Field trials were conducted at a commercial oil palm estate in Sabah using a complete randomized design (CRD) comparing DBMARK 30 EC, a commercial bioinsecticide, a chemical standard (imidacloprid + white oil), and an untreated control. Mealybug mortality, live population density, and visible sooty mould incidence were evaluated over 21 days after application (DAA). DBMARK 30 EC exhibited a strong synergistic effect in laboratory bioassays, achieving complete mortality by 96 h and significantly outperforming single-component treatments (P<0.05). In the field, DBMARK 30 EC reduced live mealybug populations by up to 86.2% at 21 DAA, comparable to the chemical standard, while markedly reducing sooty mould coverage on treated fronds. These findings demonstrate that DBMARK 30 EC is an effective and environmentally compatible bioinsecticide with strong potential for integration into integrated pest management (IPM) programs in oil palm plantations.