Abstract
Overwintered females of Argopistes coccinelliformis usually lay eggs on new leaves of host trees, such as Osmanthus×fortunei (Oleaceae) in spring and new adults emerge in early summer. However, when lammas shoots (shoots which are produced after the spring) are produced on host trees during summer and autumn, a small number of eggs are laid again, and a proportion of these can develop into adults. This study aimed to determine whether A. coccinelformis adults which develop on lammas shoots can overwinter and produce offspring the following year. Overwintered or first generation females, introduced on potted host (O. fragrans var. aurantiacus) trees with lammas shoots laid eggs on new leaves. The offspring (first and second generations) which emerged from mid-summer to autumn could overwinter when supplied with new sprouts of O. fragrans var. aurantiacus. The overwintering rate of adults was higher with progress of the season at the time of emergence. Most of the overwintered females laid eggs, and these eggs hatched. In recent years, the trimming of ornamental trees is conducted not only in winter, but also in late spring and/or summer. The result of the present experiments suggests that lammas shoot production after trimming conducted from late spring to early autumn promotes oviposition by overwintered and newly-emerged first generation adults, and as a result, trimming may provide A. coccinelliformis with an opportunity to increase their population the following year, and to increase the number of generations. It is necessary to consider the timing for trimming the branches of Oleaceae from the viewpoint of population control in A. coccinelliformis.
