G. RAMYA RISHITHA*, I. PARAMASIVA, M.S.V. CHALAM AND P. MADHUSUDAN

Department of Entomology, S.V. Agricultural College, ANGRAU, Tirupati-517 502.

ABSTRACT

The level of insecticide resistance acquired by field collected brown plant hopper populations, Nilaparvatha lugens after 24 hours and 72 hours exposure to four insecticides thiamethoxam, pymetrozine, dinotefuran, and acephate was studied in comparison with the laboratory population maintained in IIRR laboratory. Compared with the laboratory population/reference population, Maruteru population was recorded higher LC₅₀ and LC₉₀ values against thiamethoxam, pymetrozine, dinotefuran and acephate and based on resistant ratios lower levels of resistance development was noticed in Maruteru population to all the tested insecticides. The LC₅₀ values for Maruteru BPH populations were 0.129, 0.053, 0.079 and 0.149 ppm for thiamethoxam, pymetrozine, dinotefuran and acephate, respectively at 72 hrs after exposure. Whereas in laboratory BPH populations LC₅₀ values were 0.031, 0.038, 0.054 and 0.75 for thiamethoxam, pymetrozine, dinotefuran and acephate, respectively at 72 hrs after exposure. The resistance ratios for Maruteru BPH populations at LC₅₀ (72 hours after exposure) were 4.161, 1.463, 1.395, and

0.193 fold for thiamethoxam, pymetrozine, dinotefuran, and acephate, respectively.

KEYWORDS: Resistance ratios, insecticide resistance, Nilaparvata lugens, Bioassay, LC₅₀.