Abstract
Outbreaks of Aulacorthum solani occurred on soybean in Miyagi and Yamagata Prefectures, northern Honshu, extensively in 2000 and 2001, and locally in 2003 and 2004. On the other hand, such an outbreak of A. solani has never been observed in Hokkaido Prefecture. To estimate whether genotypic composition are implicated in the outbreaks on soybean, we examined the esterase patterns detected by electrophoresis of 284 clones collected in these three prefectures and five other prefectures. We also examined the susceptibility to insecticides and life-cycle category of some of them. The esterase phenotypic composition was different between Hokkaido and Miyagi/Yamagata. This was especially so in the phenotypes at the presumed esterase locus 2. In Miyagi and Yamagata the phenotypes with band F and activity (++) were frequently found, but the phenotypes with activity (±) and (−) were not found. In Hokkaido the phenotypes with activity (±) and (−) were frequently found, but the phenotypes with band F and activity (++) were not found. Any of the esterase alleles at this locus were not associated with resistance to acephate or fenvalerate. Populations in Hokkaido and northern Honshu were holocyclic and consisted of various esterase forms. These results were discussed in relation to the outbreaks on soybean.
