Population dynamics of brown planthopper Nilaparvata lugens stall and arthropod diversity on rice ecosystem with returned straw and different spectrum of insecticides

Abstract

The natural ecosystem of lowland rice in Indonesia is rich in biodiversity. However, high-intensity insecticide accompanied by a lack of organic matter in the form of straw returned to the fields causes the fragile agroecosystem, decreasing the abundance and species diversity of natural enemies, causing a broken food chain, and the tremendous potential for the outbreak of rice pests. Need study to understand the impact of returned straw and different insecticide spectrums on the diversity and abundance of arthropods and the brown planthopper (BPH) in rice fields. The experiment was located in Ciwaringin, Lemahabang, Karawang, West Java, during the rainy season from January-April 2022.The field trial was conducted under a split-plot design consisting of two main plots: rice field with and without returned straw and three subplots: without insecticide, fipronil as insecticide broad-spectrum, and triflumezopyrim as insecticide narrow-spectrum. The first insecticide was applied at an economic threshold level. Arthropods were sampled biweekly by systematically using a vacuum and insect nets. Population observation of BPH was done weekly until one week before harvest. The result showed that there are 40 morphospecies, 29 families, and 9 orders of arthropods. Based on the functional roles, there were 48.6% pests, 19.2% predators, 5.8% parasitoids, and 26.4% other role arthropods. Plots with returned straw showed a 5.4% higher abundance and diversity of arthropods than those with unreturned straw. The plot treated with triflumezopyrim showed a significantly lower population of the BPH than the plot treated with fipronil and was similar arthropod diversity to the untreated plot. In conclusion, returning straw to the paddy fields provides many ecological and economic benefits.