The repellencies of 27 essential oils against Myzus persicae (Sulzer), a vector of PVY-T, were investigated with a linear track olfactometer. Fourteen essential oils, including ginger oil and white pepper oil, repelled the aphids at a dose of 10 μl. Ginger, white pepper and carrot seed oils repelled them at even a much lower dose of 0.1 μ1. In the olfactometer test, repellencies of rosemary and ginger oils against other aphid vectors of PVY-T, Aphis gossypii Glover, A. craccivora craccivora Koch, Macrosiphum euphorbiae (Thomas) and Capitophorus formosartemisiae (Takahashi), were observed. Rosemary oil repelled A. gossypii and M. euphorbiae. Ginger oil repelled A. craccivora, M. euphorbiae and C. formosartemisiae. Therefore, the effects of rosemary and ginger oils on the alighting of M. persicae and on the incidence of yellow spotted streak caused by PVY-T were investigated in a tobacco field. The numbers of the aphids caught in the rosemary and ginger oil treated plots were 74% and 86% of their respective values in the control plots. The incidences of yellow spotted streak in both of the plots was about 50% that in the control plots. Rosemary oil showed the effect of reducing yellow spotted streak in larger areas than ginger oil. In order to develop more efficient application methods for repellents, the repellencies of rosemary oil against M. persicae were investigated using two application methods. Ethyl vinyl acetate beads soaked in rosemary oil placed on the ground around tobacco plants decreased the aphids by 31% compared with the control plot. Ropes containing rosemary oil encircling tobacco plants decreased the aphids by 37% compared with the control.
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