北海道におけるインゲンマメゾウムシの野外寄生の確認と越冬場所の推定

抄録

In several kidney bean fields in Hokkaido, adult bean weevils, Acanthoscelides obtectus, were observed staying on nearly or fully mature pods in late July and early September. The weevils were discovered only in the vicinity（less than 100 m）of residential areas among the fields investigated. On the other hand,no weevils were discovered in farm areas more than 1 km away from nearby residential areas. No weevils emerged from infested seeds stored at 0℃ for more than 35 days or stored in unheated storehouses throughout winter. These suggest that the weevils can survive winter only in heated houses in Hokkaido,where winter is cold. 7.6% and 0.4% of kidney beans harvested from two fields in the Ishikari and Iburi districts, respectively, were infested. The numbers of exit holes per infested seed were 1-9 and 1-29, with averages of 3.9 and 5.4, respectively. In these fields, the oviposition periods estimated from the adult emergence and effective cumulative temperatures, 526.3 degree-days above developmental zero, 12.8℃,were from August 4 to September 1, and from August 4 to September 9, respectively.