Effect of Methanolic Extracts of Clove (Syzygium aromaticum L.) Leaves and Galangal (Alpinia galanga L.) Rhizome for the Management of Rice Brown Plant Hopper, Nilaparvata lugens (Stal.)

Abstract

The utilization of plant-based extracts derived from clove leaves and galangal rhizome represents a potential alternative for pest control, offering relative environmental safety, particularly in the case of Nilaparvata lugens (Stal.) infestations in rice plants. The objective of this study was to determine the optimal formulation of clove leaves and galangal rhizome extracts for effective management of N. lugens on rice plants. The research was conducted at the Green House of the Pest and Plant Disease Department, Faculty of Agriculture, Sam Ratulangi University, Manado. Six different concentrations of clove leaves and galangal rhizome extracts were used, each with four replications. These concentrations were 2 ml/L, 4 ml/L, 6 ml/L, 8 ml/L, 10 ml/L and a control group. Application of the extracts employed three methods: insect spraying, plant spraying and insect-on-plant spraying. The results indicated that insect spraying with clove leaves extract resulted in a mortality rate of 43.3% to 93.3%, while galangal rhizome extract caused a mortality rate of 13.3% to 80%. Plant spraying with clove leaf extract led to a mortality rate of 6.7% to 46.7% and galangal extract resulted in a mortality rate of 6.7% to 40.0%. Insect-on-plant spraying caused mortality rates of 46.7% to 86.7% for clove leaves extract and 50% to 76.7% for galangal extract at 12 to 72 hours after application. The highest efficacy in terms of the quickest insect mortality occurred at a concentration of 10% using the insect spraying and insect-on-plant spraying methods, with mortality observed at 12 hours after application. The slowest response was observed at a concentration of 10% using the plant spraying method, with mortality occurring at 48 hours after application. The LT50 values for 10% clove leaves and galangal rhizome extracts application were determined as 18.2 hours and 24.6 hours, respectively. Therefore, clove leaves and galangal extracts can serve as viable alternatives to synthetic pesticides for the management of N. lugens, a pest of rice plants.