Pengembangan Formulasi Insektisida Nabati Ekstrak Piper aduncum dan Aglaia odorata untuk Pengendalian Plutella xylostella (Lepidoptera: Plutellidae) pada Tanaman Famili Brassicaceae

Abstract

One of the major pests that poses a significant challenge in the cultivation of Brassicaceae plants is Plutella xylostella L. (Lepidoptera: Plutellidae). Synthetic insecticides are frequently used to manage this pest; however, unwise application has led to resistance and adverse ecological effects. An alternative approach to controlling P. xylostella is the use of botanical insecticides. Piper aduncum (Piperaceae) and Aglaia odorata (Meliaceae) have shown potential as botanical insecticides. While certain plants exhibit notable insecticidal activity, their effectiveness is often limited by the phytotoxicity of their active compounds. This combination of plant extracts allows synergy of bioactive compounds, improving stability, efficacy, and reducing dosage as well as the risk of phytotoxicity and impact on non-target organisms. To facilitate field application, insecticides are formulated in a more stable and effective form. Formulations allow bioactive compounds from plant extracts to be evenly distributed, more stable during storage, and easy to apply. The emulsifiable concentrate (EC) formulation was selected for developing this botanical insecticide due to its simple production process, minimal equipment requirements, ease of application, and absence of residue on crops. The ratio of plant extracts, type of solvent, and emulsifier significantly influence the success of botanical insecticide formulations. The appropriate ratio of extracts ensures the synergy of bioactive compounds and enhances insecticidal efficacy. Selecting the right solvent affects the solubility and stability of active compounds, while the appropriate emulsifier maintains emulsion stability, reduces interfacial tension, prevents phase separation, ensures uniform distribution of active ingredients, and improves application effectiveness. These three factors must be optimized to ensure the botanical insecticide is effective, stable, and practical for field use. This study aimed to (1) investigate the bioactivity of plant extracts from Piperaceae and Meliaceae families against P. xylostella, (2) examine the compatibility of hexane extract from P. aduncum fruit and methanol extract from A. odorata twigs to enhance the efficacy of botanical insecticides, (3) develop an EC formulation of combined extracts, characterize its properties, and assess its toxicity against P. xylostella, (4) evaluate the persistence and safety of the combined extract formulation on natural enemies and its impact on broccoli plants, (5) assess the effectiveness of the combined extract formulation on broccoli crops. The study comprises five stages (1) bioactivity testing of Piperaceae and Meliaceae plant extracts against P. xylostella, including extraction using organic solvents and bioactivity assays on P. xylostella larvae. Bioactivity tests encompass toxicity evaluation (preliminary and advanced), feeding inhibition on second-instar larvae, and oviposition inhibition on P. xylostella adults, (2) compatibility and toxicity testing of mixed extracts identified in the first stage, including hexane extract of P. aduncum and methanol extract of A. odorata. Chemical composition analysis was performed using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). This stage identified synergistic mixtures, (3) stability and toxicity testing of the EC formulation combining of P. aduncum hexane extract and A. odorata methanol extract against P. xylostella. Activities included EC formulation development, stability testing, and toxicity testing of the combined extracts. A stable EC formulation with optimal active ingredient, solvent, and emulsifier composition was obtained, (4) persistence and effectiveness testing of the EC formulation on natural enemies and plants. Tests included evaluating the formulation’s safety for natural enemies, its phytotoxicity, and persistence, (5) field efficacy testing of the formulation, including its effect on P. xylostella larval populations, parasitism rates, and arthropod diversity. The results showed that the hexane extract of P. aduncum and methanol extract of A. odorata were effective in controlling P. xylostella larvae. The LC50 and LC95 values of P. aduncum hexane extract were 0.07% and 0.14%, respectively, and A. odorata methanol extract were 1.63% and 4.71%, respectively, against second-instar larvae of P. xylostella at 96 hours after treatment. At the higher concentrations, the P. aduncum hexane extract (0,07%) and the A. odorata methanol extract (1,77%) exhibited strong feeding inhibition activity, with inhibition rates of 95.08% and 96.09%, respectively. Additionally, these extracts effectively inhibited oviposition activity, with inhibition rates of 78.53% and 79.02%, respectively. Compatibility testing of the P. aduncum and A. odorata extract mixture revealed that a 2:1 (w/w) ratio exhibited a synergistic effect. The extract mixture was then formulated into an emulsifiable concentrate (EC). Emulsion stability testing showed that the most stable formulation consisted of a hexane extract of P. aduncum and a methanol extract of A. odorata (2:1; w/v) with a composition of 50% plant extract, 30% xylene as a solvent, and 20% Tween 80 as an emulsifier. The EC formulation of the botanical insecticide does not show phytotoxicity on plants, is safe for natural enemies, and has a short persistence. The EC formulation of the botanical insecticide (2:1; w/v) effectively suppresses the population of P. xylostella in the field, with an effectiveness comparable to the insecticide emamectin benzoate (Emacel 30 EC), and does not affect the arthropod population. The results of this study indicate that the EC formulation of the mixed hexane extract of P. aduncum and methanol extract of A. odorata (2:1; w/v) has the potential to be developed commercially as a botanical insecticide formulation for controlling P. xylostella larvae.