Efficacy of insecticides in controlling the rice gall midge (Orseolia oryzae (Wood-Mason)), in rice fields of lower northern, central, and eastern regions

Abstract

The rice gall midge, Orseolia oryzae (Wood-Mason), is an important insect pest of rice. In recent years, outbreaks have become increasingly severe in irrigated rice fields in Thailand’s lower northern, central, and eastern regions. These areas primarily cultivate rice for commercial purposes. This study aimed to evaluate the effectiveness of insecticides registered for use in rice fields in controlling the rice gall midge, which has shown expanding infestations. Field trials were conducted in farmers’ fields in Nakhon Nayok and Chai Nat provinces during the 2024-2025 dry season. A randomized complete block design (RCBD) with three replications was employed. The rice variety used was RD85, and insecticides were applied when rice plants were 25-40 days old after sowing. Spraying was carried out when rice plants exhibited gall midge damage symptoms (silver shoots) and the percentage of damage reached the economic threshold level. The insecticides tested were ethiprole 10% SC, fipronil 5% SC, acetamiprid 20% SP, clothianidin 16% SG, thiamethoxam 25% WG, spinosad 12% SC, novaluron 5.67% + indoxacarb 4.86% SC, chlorantraniliprole 5.17% SC, flubendiamide 20% WG, and distilled water as the control. Applications were made using a motorized knapsack mist-blower sprayer. The results showed that, in both seasons, all insecticide treatments provided control efficacy against the rice gall midge ranging from 55 to 79% after the final application. All insecticide treatments resulted in significantly higher rice yields (747–1,050 kg/rai) compared with the control, which produced the lowest yields (502–521 kg/rai). Therefore, when rice gall midge infestations reach the economic threshold level, effective and relatively low-cost insecticides can be used as decision-support recommendations for control when necessary, including thiamethoxam 25% WG, clothianidin 16% SG, acetamiprid 20% SP, novaluron 5.67% + indoxacarb 4.86% SC, and flubendiamide 20% WG. It is recommended that only one insecticide be selected and applied according to label recommendations,