Cerbera odollam extracts as eco-friendly botanical insecticides against Arthroschista hilaralis Walker

BACKGROUND AND OBJECTIVES: Arthroschista hilaralis Walk. is an insect pest that poses a significant threat to Neolamarckia cadamba trees, adversely affects plant growth, and potentially causes death in severe attacks. The current study examines how botanical insecticides can serve as an eco-friendly approach to pest management, with a specific focus on Cerbera odollam. This study aimed to assess the insecticidal effectiveness of methanol extracts and n-hexane fractions from Cerbera odollam leaves and seeds against Arthroschista hilaralis larvae and identify the bioactive compounds responsible for the insecticidal effects. METHODS: This study assessed the toxicity of methanol extracts and n-hexane fraction derived from Cerbera odollam leaves and seeds against second and third-instar larvae of Arthroschista hilaralis. Laboratory and nursery bioassays were conducted using three concentrations: 0.25 percent, 0.5 percent, and 0.75 percent alongside a control group to assess mortality and developmental inhibition of Arthroschista hilaralis larvae. Active compounds were identified through phytochemical screening and gas chromatography-mass spectrometry analysis. Mortality, pupation, and adult emergence data were analyzed using probit analysis to estimate lethal concentration 50 and lethal concentration 95 values. FINDINGS: After 72 hours of exposure, the lethal concentration 50 values of methanol seed and leaf, and n-hexane seed and leaf on the second instar were 0.44, 0.64, 0.40, and 0.52 percent, respectively. While on the third instar were 0.52, 0.64, 0.44, and 0.57 percent, respectively. The n-hexane fraction of Cerbera odollam seed extracts was the most effective in inducing Arthroschista hilaralis larval mortality. The n-hexane fraction, measuring between 0.5 and 0.75 percent from Cerbera odollam seeds, led to an 80 to 100 percent mortality rate in second and third-instar larvae. The n-hexane fraction of Cerbera odollam seeds extended the pupal development period by 2.0 to 2.67 days compared to the control group. Cerbera odollam leaf and seed extract contains significant chemical substances that are biologically active, including fatty acids, phenolic compounds, terpenoids, amines, esters, and hydrocarbons. The main constituents recognized for the insecticidal effects of Cerbera odollam include trans-β-ionone (11.85 percent), acetamide (9.31 percent), and α-copaene (9.61 percent). CONCLUSION: This study highlights Cerbera odollam, particularly its n-hexane seed fraction, as a highly effective, eco-friendly insecticide against Arthroschista hilaralis. The bioactive elements resulted in full larval death and hindered developmental processes. Supported by nursery trials, Cerbera odollam offers a promising, sustainable solution for integrated pest management in N. cadamba forestry, reducing reliance on synthetic pesticides and supporting environmental conservation.