Cotoneaster を加害するルリカミキリについて

Abstract

Pear borer, Chreonoma fortunei japonica Gahan, is a famous borer which is very injurious, especially to apple, pear and peach trees in Japan. This beetle feeds on the living stem or the twigs of various kinds of trees which belong to the family Rosaceae. (1) Host plants 20 species of Rosaceae were already reported as host plants of this beetle. Besides, the writers have recently found the living stem of Sorbus japonica, S. alnifolia, Pyracantha crenulata, and Photinia serrulata, Stranvoesia undulata, infested with larvae of this species. (2) Damage to Cotoneaster Cotoneaster is a valuable shrub for landscape effects in Europe and America. 40 species of them are collected in the Kamigamo breeding experimental station of Kyoto University. Some of them, namely Cotoneaster bullata, C. bacillaris, C. frigida, C. francheti, C. hebephylla, C. nitens, C. recemiflora, C. pannosa were attacked heavily by this beetle. (3) Life history Although, the life history of this beetle was well known, writer's observations in Kyoto are as follows. The adult appears from early to late May in Kyoto. The adult feeds on the nerves of new leaves from the back side, and, occasionally, the thin bark of the young twig, and shortly afterward begins to oviposit. The adult gnaws, in oviposition, horse-shoe pits through the bark and then inserts in each pit a single egg beneath the bark scales of living twigs or stems. After about 10 days, the larva hatches out. For a short time, the larva feeds beneath the bark, so the bark is stripped, but soon it enters the trunk and excavates an extensive mine. The larva hibernates over two winters. Pupation takes place in April. The dimension of trees suitable for the attack is 1 ~ 1.5cm in diameter. The gallaries of the larvae are comparatively short, measuring from 5 to 12 cm in length. The damage is not severe enough to kill the shrub, but the infested portion considerably loses its strength and tends to be broken by some external causes, for instance, wind and snow. Furthermore, the type of shrub becomes unnatural. 2 species of parasite bees, Cryptini sp. Dolichomitus sp, were found and the parasites emerged at about the same time as the adults of the beetle. Citrus borer, Anoplophora malasiaca, bored at the base of the stem of C. frigida, too.