Pesticide Resistance and Related Mutation Frequencies of Tetranychus urticae in Hainan, China

The two-spotted spider mite, Tetranychus urticae, is an important pest of horticultural crops worldwide and has developed resistance against multiple kinds of pesticides. To date, information on the resistance to pesticides is inadequate for T. urticae populations in Hainan, south China. In the current study, we determined the resistance to seven pesticides in five field populations of T. urticae that were collected on cucurbit crops in Hainan in 2021. The results showed that T. urticae populations developed high to extremely high resistance to abamectin and bifenthrin and medium to high resistance to pyridaben, profenofos, and cyflumetofen. However, four of the five populations were either susceptible to or had only low resistance to bifenazate and B-azolemiteacrylic. We also determined the frequencies of mutations previously associated with T. urticae resistance to abamectin, pyrethroids, organophosphates, bifenazate, or pyridaben; mutation frequencies as high as 100% were detected for some of the mutations in some of the populations. The results should facilitate the development of rational strategies for the chemical control of T. urticae populations in Hainan, China.