Developmental and reproductive performance of Tetranychus pueraricola Ehara and Gotoh (Acari: Tetranychidae) at four constant temperatures

The spider mite Tetranychus pueraricola infests kudzu vines throughout Japan and causes conspicuous brownish feeding scars. It is possibility that T. pueraricola may get out of hand after invasion of agricultural leguminous crops. To better evaluate its potential severity as a pest, we determined the development, survivorship and life-history parameters of T. pueraricola on kidney bean. At temperatures between 15 and 30 degrees C more than 89% of eggs hatched and of the newly hatched larvae ca. 89% attained maturity. There was no significant difference in eclosion rate of eggs or survival rate of immature stages among the temperatures. The lower threshold temperature from egg to oviposition was 10.9 degrees C and the thermal constant was 147.1 degree-days. Based on these data, the maximum number of generations that can theoretically complete development under average field conditions in Ibaraki, Central Japan is between 11 and 14 generations per year. At 25 degrees C, females laid on average 125 eggs during a mean oviposition period of 12.6 days. The intrinsic rate of natural increase (r(m)) was 0.102 at 15 degrees C, 0.179 at 20 degrees C, 0.299 at 25 degrees C and 0.377 at 30 degrees C. Thus, T pueraricola has the second highest r(m)-value among tetranychid mites reported so far at 25 degrees C, with T .okinawanus having the highest (0.316). This indicates that T. pueraricola has the potential to become a serious pest on agricultural crops.