Assessment of Economic Damage Caused by Rice Insect Pests in Post-Flooded Paddy Fields

Abstract

The purpose of this study was to investigate the population of rice pests and natural enemies in the rice fields of Sakon Nakhon and Nakhon Phanom provinces after flooding. The aim

was to assess the extent of damage caused by changes in pest populations relative to natural enemy populations.  Three study areas were selected: Muang District, Sakon Nakhon Province, Khok Sri Suphan District. Sakon Nakhon Province and Na Wa District Nakhon Phanom Province. In each district, four plots were surveyed. Insect data were collected based on the rice growth stages: seedling stage, panicle initiation stage, and maturity stage. An insect net was used to sample populations at five diagonally distributed points per plot according to the sampling plan.

The results showed that in Mueang District, Sakon Nakhon Province, the ratio of rice insect pests to natural enemies was 2.23:1, with an average of 69.03% pests and 30.97% natural enemies. InKhok Si Suphan District, Sakon Nakhon Province, the ratio was 2.35:1, with an average of 70.12% pests and 29.88% natural enemies. In Na Wa District, Nakhon Phanom Province, the ratio increased to 3.04:1, with 75.26% pests and 24.74% natural enemies. Additionally, it was found that pest populations were highest during the panicle initiation stage, followed by the seedling stage and the maturity stage, respectively. The results suggest that the pest-to-natural-enemy ratios in all three study areas indicate damage levels not exceeding 25%, which is within the threshold of natural ecological balance. This balance is attributed to the presence of predatory natural enemies capable of controlling rice pests from the egg to adult stages across all districts studied.