サツマイモ食葉性害虫の生態 ＩＩ 主要害虫の成虫の発生消長

Abstract

Seasonal occurrence of adults of four major sweet potato defoliators, Aedia leucomelas LINNÉ, Agrius convolvuli LINNÉ, Brachmia triannulella (HERRICH-SCHAFFER) and Spodoptera litura FABRICIUS, was examined from 1983 to 1985 at Kushira in Kagoshima. Adults of A. leucomelas were captured with light and molasses-traps from early May to mid-November. Peak catches occurred in mid-June-early July, mid-July, early August and September. Moth numbers increased gradually from the first peak to the highest peak in September. A. convolvuli was caught from late May to mid-October in a light-trap. Almost all of the total annual moth catches occurred in August and September. Moths of B. triannulella, which overwinter at the adult stage, were counted visually by the moth-flushing method (the surveyor walks along the nursery beds of sweet potato and brushes the plants with a rod) from late April to early November. Two major peaks occurred in May and June. The first peak was higher than the second in the last two years. Many moths of S. litura were captured with light and molasses-traps from August to November. The peak in number occurred from early to mid-September. The number of individuals captured with a pheromone trap (Pherodine SL R ) greatly exceeded that of the individuals captured with other traps. Moths were abundant in September and October. Population density of A. leucomelas and A. convolvuli in August seemed to be higher than that reported by MIYAHARA et al in 1963-66. This may be due to the change of the cultivation methods of sweet potato. Namely, adults of A. leucomelas, A. convolvuli, which emerged in early and late May, respectively, were able to lay their eggs on the leaves of sweet potato which had already been transplanted in late May according to recent cultivation methods. As a result, the moth populations of the following generation increased in the August period. Such a phenomenon was not observed in S. litura presumably due to the food habits of the larvae of this insect which is polyphagous.