Studies on the Cold-Hardiness and Overwintering of Spodoptera litura F. (Lepidoptera: Noctuidae). V. Possibility of Larval and Pupal Overwintering at the Southern Extremity of the Boso Peninsula

Abstract

Overwintering of larvae and pupae of S. litura was investigated in an unheated greenhouse in Tateyama and in fields at Tateyama and Wada, in the southern Boso Peninsula, over three winters from 1985 to 1988. The larvae survived the mild winters of 1986-1987 and 1987-1988 in fields at Tateyama and Wada. However, they did not survive the relatively cold winter of 1985-1986 at Tateyama. The survival rate of younger larvae was higher than that of older ones. The lowest temperature at Wada in 1987-1988 was -3.5°C, which is higher than the lethal temperature of -5°C. Wada is a warm place because the northwest side is surrounded by mountains that block cold winds. For larvae to survive winter, an effective temperature of more than 0.9°C per day is necessary. The number of days meeting this criterion during the test period in 1987-1988 at Wada was 59 accounting for 74% of the test period. Third and 4th instar larvae were released in an unheated greenhouse in mid-December of 1985. Fifty nine percent of the larvae pupated and 31% emerged as adults by the end of March. When pupae were placed in the soil in an unheated greenhouse, they survived until mid-February but did not emerge normally. © 1992, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.