2026 Volume 68 Pages 15-21
To facilitate integrated pest management in Raphanus sativus (Daikon, Japanese radish), we surveyed two areas where R. sativus is cultivated in Shizuoka Prefecture, central Japan. We assessed the percentage of R. sativus plants colonized by leafminers on the leaves, parasitism rates by hymenopteran parasitoids on leafminers, and parasitoid species composition. The percentage of colonized leafminers ranged from 0.6–28.2 and 0–28.6% in the Mikatahara and Haibara areas, respectively. The majority of leafminers were Chromatomyia horticola, with a few Liriomyza trifolii. Additionally, the parasitism rate of parasitoids on leafminers varied from 8.3–79.5% (average 52.0%) in the Mikatahara area and from 0–48.6% (average 17.3%) in the Haibara area. These differences are likely because of variations in the surrounding crop cultivation conditions, wind speed, and pesticide application history in each area. The parasitoid community was primarily dominated by Diglyphus isaea, followed by Diglyphus minoeus (Eulophidae). Dacnusa sasakawai and Halticoptera circulus were the dominant parasitoids in the families Braconidae and Pteromalidae, respectively. The dominance of these parasitoid species was attributed to variations in their optimum temperature and pesticide susceptibility. Additionally, there were a few differences in species composition among the areas. These results indicate that natural enemy parasitoids significantly suppress leafminer density on R. sativus. Moreover, it was revealed that the parasitism rate of leafminer parasitoids varied significantly by region. The effective use of these natural enemy parasitoids requires identifying pesticides that minimally affect them and determining the optimal temperature for each parasitoid species.
