Abstract：In order to understand the different resistance level of Prodenia litura living in different regions to the 3 kinds of organophosphorus pesticides used in common, toxicity tests to the 3rd instar larvae of Prodenia litura were carried out in laboratory using leaf dipping method. The result showed that resistance level to Chlorpyrifos increased slowly, the highest level only achieves 5.57 times of the original. Phoxim takes the second place. Its resistance level achieves 2.57-20.74 times. While the highest resistance multiple to Acephate can achieve 109.46 times. The toxicity of these 3 kinds pesticides from high to low was Chlorpyrifos, Phoxim, Acephate.
