カンキツ病害虫の共同防除地区における捕食性甲虫類

抄録

The ecological investigation was carried out on the predaceous Coleoptera in various citrus orchards in the collective pest-controlled area, Chiziwa-machi, Nagasaki Prefecture, Japan, and the following results were obtained. In either controlled or uncontrolled citrus orchards, the population densities of Pseudoscymnus hareya, Hyperaspis japonica, Stethorus japonicus, Scymnus rectus, Scymnus ishidai and Telsimia nigra were relatively high. Only in the controlled orchard, Pseudoscymnus hareja and Stethorus japonicus were found comparatively in large numbers. Comparison of the predator density between the controlled and uncontrolled orchards revealed that the density in the former was much lower than that in the latter, being as low as only about 1/10. In the controlled area, the larger number of species and a little higher predator density were found in the adult tree orchards (tree age above 10 years) whereas in the young tree orchards (tree age below 10 years) the predators of the scale insects were not found at all but only the predators of aphids and citrus red mites. Thus, there was a difinite relation between the predator and pest densities. The predator density was low immediately after the spray of pesticides, and showed a gradual increase with the lapse of days. Comparison of the number of all insects other than the major pests between the controlled and uncontrolled orchards showed that relatively large numbers of both Coleoptera and Hymenoptera were found in the uncontrolled orchards.