Yellowing and dwarfing of soybean plants occurred in an area with a high-density population of the citrus leafhopper Apheliona ferruginea Matsumura Hemiptera: Cicadellidae: Typhlocybinae in Mie Prefecture, Japan. In two laboratory experiments, we examined whether these symptoms were induced by the insect itself or by a pathogen transmitted by it. In Experiment 1, internode lengths were significantly shorter at 17 days after infestation of soybean seedlings by A. ferruginea than in the control plants. In Experiment 2, newer internode and petiole lengths were significantly shorter at 17 and 37 days after infestation than in the control plants, but 20 days after the removal of the insects on Day 17, those of later leaves did not differ significantly from the controls. We conclude that the yellowing and dwarfing of soybean plants infested by A. ferruginea are induced by the insect itself, not by a pathogen transmitted by it, because the occurrence of the symptoms was restricted to the insect infestation period.