Development and adult survival of the sweet potato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae), during winter on Amami-Oshima Island, Japan.

Abstract

We investigated the development and adult survival of Cylas formicarius (Fabricius) during winter on Amami-Oshima Island, Japan. Every developmental stage of the weevil (except for eggs, which were not examined) was found in sweet potato tuberous roots during winter, and adults and third instars were dominant. The weevils in sweet potato roots continued to develop during winter, although their development was delayed due to low temperatures. In addition, adult weevils continued to emerge from the host plants throughout winter. Most adult weevils were found under stones and fallen leaves on the ground surface and within the top 5 cm of soil in a sweet potato field during the daytime in winter, and scarcely dispersed from the host plants in winter. The adult weevils released in a sweet potato field and a field cage in December or later survived until the following late March or late April. The results suggest that most of the females that started to oviposit after overwintering came from eggs laid in the previous September and October.