2022 Volume 64 Pages 18-22
The seasonal prevalence of the tortoise beetle, Laccoptera nepalensis Boheman, recently introduced to the Kinki region in Japan, was investigated in southern Osaka Prefecture. This was done once a month from May to December 2021. The numbers of larvae, pupae, and adults were recorded at four sites on morning glory vines, Ipomoea spp., and three sites on sweet potato, Ipomoea batatas. Adults were found on the morning glory vines in all months investigated. Adult density decreased in June and gradually increased in summer and autumn. Larvae were found after June at all sites and the densities were relatively high in June, September, and October. At the sweet potato sites, adults were first recorded in July, August, and September, depending on the site, and densities were relatively high in September and October. The larvae were observed between August and November. A rearing experiment was conducted on the southern Osaka population under various temperature conditions. The mean periods between oviposition and adult emergence were approximately 54 and 31 days at 20 and 25°C, respectively. The developmental threshold (t0) and thermal constant (K) for the entire immature stage were 10.8°C and 637 day-degrees, respectively. The number of possible generations estimated from the effective accumulative temperature and temperature was calculated to be up to three in the southern Osaka population.
