Impact of Insecticides on Natural Enemy Diversity in Chainat Province's Paddy Fields

Abstract

Predators and parasitoids, they are nature enemies that an important part to the biological control of rice insect pests and maintaining of the ecological balance in rice fields. In general, there were only four to five major species of rice insect pests in the rice field, and farmers commonly used insecticides as a preventative and eradication method since it's a comfortable and fast strategy. This study aims to investigated the effects of insecticides on the diversity of natural enemies in rice fields. The study conducted during in January – April, 2023 at farmer's field in Hankha District, Chainat Province for four treatment and five replicates have been used in the RCBD experimental plan. 50 days after rice of Pathum Thani 1 was sown, three types of insecticides—clothianidin 16% SG imidacloprid 10% SL and ethiprole, 10% SC were sprayed using a motorised backpack mistblower at the labeled rate, utilizing 60 liters of water per rai. Samples of rice insect pests and their natural enemies were collected one day before insecticide spraying and seven to fifteen days after the application of insecticide using the D- vac insect vacuum equipment. The experiment's findings revealed six orders of natural enemies both before and after applying insecticides. Following a 15- day spraying period, the abundance of natural enemies from the orders Hemiptera Diptera Odonata and Araneae was found to have decreased, while the number of predatory natural enemies from the order Diptera and the number of natural enemies from the orders Coleoptera and Hymenoptera increased. The abundance of rice insect pest from the orders Hemiptera, which include the brown planthopper white-backed planthopper green leafhopper and the zigzag leafhopper had decreased (before spraying 98.27 percent, after spraying 77.47 percent), the order Thysanoptera had increased (before spraying 1. 73 percent, after spraying 22. 18 percent) . In terms of side effect category, clothianidin 1 6 % SG and imidacloprid 1 0 % SL were shown to be harmless to natural enemies, but natural enemies were slightly harmful by ethiprole 1 0 % SC. Following a 15- day spraying period, all treatments indicated an increasing tendency for the Shannon-Wiener diversity index. The Shannon-Wiener diversity index highest at 1.34 before spraying and reached 1. 51 following a 15- day spraying period. The results obtained in this study can be utilized to inform decisions and advise farmers on the application of insecticides that minimizes the impact on the diversity of natural enemies in rice fields. Keywords: Rice, Side effect, Insecticide, Biodiversity,