Tetranychus evansi Baker & Pritchard occurs on solanaceous plants, and causes serious damage to a variety of crops in Africa and Europe; it has not been reported from Japan. Tetranychus takafujii Ehara & Ohashi was found on Solanum nigrum L. in Japan in 2001 and described as a new species in 2002. It is considered to be a Solanaceae-specialist too and it is feared to become a severe pest on solanaceous crops, once it invades them. Because T. takafujii is morphologically very similar to T. evansi, doubt has arisen about the difference between these two species. Here we avoid the issue of taxonomy and focus on a solution for the potential problems that may arise when either of the species invades solanaceous crops. The present study determines the susceptibility of three T. takafujii populations from Japan and six T. evansi populations from various countries to 11 acaricides. The LC50-values of all nine populations tested were lower than the recommended concentration of every acaricide. These results suggest that mites from all nine populations can be controlled with acaricides when they occur on crops.

• Satoshi Fujiwara(Laboratory of Applied Entomology and Zoology, Faculty of Agriculture, Ibaraki University, Japan)
• Yasuki Kitashima(Laboratory of Applied Entomology and Zoology, Faculty of Agriculture, Ibaraki University, Japan)
• Tetsuo Gotoh(Laboratory of Applied Entomology and Zoology, Faculty of Agriculture, Ibaraki University, Japan)