Overwintering stages of Callosobruchus chinensis (L.) in the field

Adzuki bean beetle,Callosobruchus chinensis, is a worldwide oligophagous and a field-to-storage pest of legumes including adzuki beans (Vigna angularis). Its over-wintering stage is yet to be confirmed. A series of experiments was carried out at Jinju, in the southern part of the Republic of Korea, to elucidate the overwintering stages. Top- and sub-soil samplings followed by pod and seed samplings from left over plants from adzuki bean fields in the winter of 2015, and an outdoor overwintering test (during Nov 2018 to Jun 2019) by exposing bean seeds harboring different stages (eggs, larvae, pupae, pharates and adults) of laboratory rearedC. chinensisto the winter environment were carried out. None of theC. chinensisstages was detected from the top- and sub-soil samples. When the pods and seeds from left over plants were sampled, only a few live pupae were obtained. In the outdoor test with laboratory rearedC. chinensis, all the stages (larvae, pupae, and adults), except eggs, were detected on every other weekly samples of infested adzuki bean seeds throughout the winter. These results showed that the overwintering stages ofC. chinensisin Jinju, southern Korea, are larvae, pupae, pharates and adults.