Infestation of four Japanese orchids by flies, including Japanagromyza tokunagai

Fly infestation of wild orchids is widely recognised in Japan. The flies feed on the orchid fruit and prevent seed production. To protect orchids from fly infestation, it is necessary to identify the fly species, degree of damage to each orchid species, infested organs, and seasonal changes. This study investigated the degree of damage to four Japanese orchid species and identified the collected flies using molecular methods. We found Japanagromyza tokunagai (Sasakawa) (Diptera: Agromyzidae) on all four orchid species collected from Fukushima, Ibaraki, Chiba, and Kochi Prefectures. The fruits of Liparis nervosa (Thunb.) Lindl. and Phaius flavus (Blume) Lindl. and the flower stalks of Calanthe puberula Lindl. and Goodyera schlechtendaliana Rchb.f. were infested by the flies. The infestation of flower stalks caused deterioration of the flowers and prevented seed production in the latter two orchids. No fly damage was found on G. schlechtendaliana collected in Hokkaido Prefecture, but plants from Fukushima Prefecture were damaged, suggesting that the degree of damage differs regionally. Our results indicate that flies threaten many orchid species and that the control of J. tokunagai is an important issue for orchid conservation in Japan.