Regional Susceptibilities ofRhopalosiphum padi(Hemiptera: Aphididae) to Ten Insecticides

Rhopalosiphum padi (L.) (Hemiptera: Aphididae) is one of the most significant cereal pests worldwide. Control of R. padi has relied heavily on chemical insecticides. We sampled 12 populations of R. padi from 11 provinces in China and analyzed their regional susceptibilities to 10 insecticides by using the leaf dip method. The R. padi populations showed susceptibility or minor resistance to chlorpyrifos, malathion, thiamethoxam, beta-cypermethrin, acetamiprid, and pymetrozine, but minor to moderate resistance to bifenthrin, decamethrin, and abamectin. Correlation analysis indicated positive and significant correlations between R. padi resistance levels to thiamethoxam and beta-cypermethrin, between R. padi resistance levels to chlorpyrifos and 4 other insecticides (decamethrin, abamectin, acetamiprid, and beta-cypermethrin), and between R. padi resistance levels to acetamiprid and 3 other insecticides (decamethrin, thiamethoxam, and beta-cypermethrin). Due to the widespread and variable nature of resistance in R. padi, we strongly urge rotation of insecticide classes to delay the onset of high levels of resistance.