Semiochemical mediated host plant preference in the yellowmargined leaf beetle, Microtheca ochroloma Stål (Coleoptera: Chrysomelidae)

The yellowmargined leaf beetle (YMLB),Microtheca ochroloma Stål (Coleoptera: Chrysomelidae) is a serious pest of cruciferous crops in southeastern U.S. Laboratory and greenhouse experiments were conducted to evaluate relative attraction of this beetle to different cruciferous host plants including turnip (Brassica rapa L.), cabbage (B. oleracea var Capitata L.), collards (B. oleracea var acephata), and napa cabbage (B. pekinesis (Lour)). Results from four -choice olfactometer bioassays demonstrated the odor-mediated attraction of YMLB adults and larvae to all four tested host plants. However, more insects were attracted to turnip and napa cabbage than to cabbage and collards. Similar results were obtained in the greenhouse experiments: significantly greater numbers of adults and larvae were recorded on turnip and napa cabbage, compared to the other host plants. These results suggest that the observed field preference of YMLB for turnip and napa cabbage is odor-mediated.