Characterization of Overwintering Behaviors and Sites of Bean Bug, Riptortus pedestris (Hemiptera: Alydidae), Under Laboratory and Field Conditions

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is a major agricultural pest on leguminous plants and tree fruit in South Korea and Japan. Only anecdotal information is currently available about its overwintering behavior and ecology. Therefore, we conducted laboratory experiments and field sampling to characterize overwintering structures and landscapes that R. pedestris use and prefer in South Korea. Under laboratory conditions, we identified the overwintering structure preference of R. pedestris adults and analyzed their spatial distributions. Among tested structures including pile of rocks, rotten wood, and leaf litter, R. pedestris was almost exclusively found in leaf litter. Spatial analysis using Spatial Analysis by Distance IndicEs (SADIE) indicated that most overwintering R. pedestris showed no spatial-aggregation behavior in the test arena. Field surveys were also conducted to characterize overwintering landscapes during the two winter seasons between 2014 and 2016. We selected two distinct landscapes: mountain areas and agricultural areas. Mountain areas were high-elevation mountains remote from agricultural practice, whereas agricultural areas were low-elevation forested landscapes adjacent to agricultural fields, including soybeans. From the 2-yr field survey, 92% (11 out of 12 individuals) of overwintering R. pedestris were found in the agricultural area without a significant aggregation pattern.