Does Background Odor in Tea Gardens Mask Attractants? Screening and Application of Attractants for Empoasca onukii Matsuda

Plant volatiles help herbivores to locate their hosts, and therefore, they could be used to help develop pesticide-free pest management strategies. To develop an attractant for tea leafhopper (Empoasca onukii), we screened nine tea plant volatile compounds for their attractiveness using Y-tube olfactometer assays. Results indicated that tea leafhoppers significantly preferred ocimene, limonene, (Z)-3-hexenol, and (Z)-3-hexenyl acetate over clean air. These compounds were combined in a blend which lost its attractiveness at concentrations below 10-2 g/ml in liquid paraffin. In field tests, the blend was attractive to leafhoppers only in autumn, but not in summer. Analyses of the tea field background odor showed that all four components of the blend were present at much higher concentrations in summer (0.05-0.001 ng/liter) than in autumn (~10- to 25-fold lower). In field Y-tube bioassays, compared with the tea field background odor, the blend was attractive at a concentration of 10-1 g/ml in liquid paraffin, but not at 10-2 g/ml. These results suggest that field background odor can disrupt the attractiveness of an attractant based on plant volatiles to herbivores.