Riptortus pedestris is a major agricultural pest in Korea. To manage this pest, it is necessary to understand the complete life history of R. pedestris. However, most studies have focused on the summer period when the pest attacks crops. Therefore, we conducted laboratory and field experiment to identify overwintering behavior of adult R. pedestris. First, we conducted two laboratory experiments to examine overwintering habitat preferences and spatial distribution of R. pedestris in the habitat. Second, we conducted field survey to characterize overwintering sites of R. pedestris in diverse landscapes. In the laboratory conditions, R. pedestris almost exclusively showed overwintering behavior in the leaf litter arena (63%) among the structures tested (rocks: 3%; rotten wood: 0%). And spatial distribution of R. pedestris showed solitary behavior in leaf litters. In the field, we located 12 individuals of overwintering adults from the urban areas, whereas no individuals were found from the high-elevation mountains and agricultural landscapes. Our results suggest that R. pedestris mainly use leaf litter as an overwintering structure, with solitary behavior, and low-elevation forested areas near urban landscapes seem to be more preferred overwintering sites.

사과 재배포장에서 점박이응애(Tetranychus urticae Koch)의 월동은 사과나무의 여러 장소에서 5~15마리의 성충 암컷이 개체군을 형성하 여 월동하는 것으로 밝혀졌다. 월동중인 암컷들은 대부분 복숭아순나방(Grapholita molesta) 유충의 고치가 있는 조피사이의 갈라진 틈에서도 발 견되었으며, 부주지 상에 형성된 좁은 조피틈과 과실 수확 후 남아있는 꽃자루에서도 발견되었으나 월동 개체수는 매우 적었다. 또한, 월동중인 암컷들은 결과지의 기부에 형성된 거친껍질 및 눈의 기부, 여러 작은가지의 분지부위 좁은틈에서도 발견되었다. 한편, 수체상에 형성된 일부 점박 이응애 월동장소로 죽은 개각충속, 깍지벌레 빈껍질속, 진딧물의 미라속에서도 발견되었는데, 이들 장소에서의 월동 응애수는 매우 적었다. 2년 에 걸쳐 수행된 본 연구에서 점박이응애의 월동중 암컷 성충의 사망률은 평균 72~80%로 매우 높았으며, 이는 이들 응애가 겨울 동안 추위에 견 디는 저항력이 낮기 때문으로 판단되었다.

R. pedestris is a major insect pest in agricultural production, especially on soybean and tree fruit, in Korea. Currently, the management of this pest relies mainly on insecticide application in most commodities. However, the chemical controls cause numerous environmental problems. To develop sustainable management tools, it is fundamental to understand the basic biology and ecology of R. pedestris. However, the overwintering ecology of this pest is virtually unknown. In this study, we surveyed diverse landscapes including high elevation mountains soybean fields and there neighboring forests to find and characterize the overwintering sites of R. pedestris. In the field, we sampled leaf litters from 1㎡ grids to locate overwintering R. pedestris. The samples were taken every 100m altitude in the mountain areas or every 50m distance in the flat landscapes. Overwintering R. pedestris were found from 6 samples out of 137 samples. All overwintering R. pedestris were located from forested areas adjacent to urban landscapes in Seong-Nam si, Gyeong-Gi Do. Interestingly, no overwintering R. pedestris was found from in the samples collected from high elivation mountains including Yeon-In, Song-Ni, Chi-Ak, Ga-Ya, Wol-Chul. likewise, no overwintering individual was found from soybean fields and their neighboring forested areas. With caveat that the data were collected only for 1 year, our results support that R. pedestris overwinters solitary resulting in low detection rates from the samples. Given that R. pedestris typically disperse into cultivated crops with high densities, it is important to better understand environmental factors affecting the presence or absence of overwintering R. pedestrris in diverse landscapes. The knowledge would be essential to develop sustainable monitoring and management programs for this economically important pest in Korea.

Insects in temperate climate zones are challenged to endure harsh temperature regimes and the absence of food resources during winter. Many insects overwinter in diapause at different sites. The overwintering sites differ according to the insect species. The study was conducted to investigate the overwintering sites between the two orchard systems for the Grapholita molesta larvae. Overwintering sites of Grapholita molesta were found different between apple grafting systems. More individuals favored the side branches and main bottom trunk as overwintering sites in big tree system (M26) and in dwarf grafting high density system (M9) respectively. There was no significant different between M9 and M26 cultivars in the relative proportion of larvae. However, significant differences were found in the interaction between the overwintering sites and the two M9 and M26 cultivar orchard systems. The natural mortality from the field was estimated as 22.1% and 18.3% from dwarfing, high density orchards and the big tree orchard systems respectively. This study provides valuable information and guidelines to understand the major overwintering sites within different orchard systems for scheduling management actions against spring adult moths population emergence.

Neoseiulus californicus (McGregor) is a potential biological control agent of spider mites in orchards. The field occurrence of this species was first reported from citrus orchards in Jeju Island and recently this mite started to be sold as a commercial product in Korea. However, the natural occurrence of N. californicus in the Korean mainland is unclear or quite limited. At this time, it is not certain whether N. californicus can overwinter in the Korean mainland or not. This mite is presently planning to be used as a biological control agent against spider mites in apple orchards of the Korean mainland. The main objective of this study was to investigate natural overwintering sites of N. californicus and possible factor increasing winter survival of this species, to develop effective method for collecting overwintering population of N. californicus. For the first objective, we conducted field survey in two citrus orchards of Jeju in early and late February 2008. Samples were collected from various possible overwintering sites: citrus trees, ground covers and windbreaks. Total 259 phytoseiid mites were collected, 94% of the mites were identified as N. californicus and 98% of them were adult females. Most of N. californicus were collected from ground covers, specially the weed species which had rosette leaves: Youngia japonica (L.) DC. and Erigeron spp. This result seemed to suggest that N. californicus try to hide beneath weed leaves near ground surface during winter to get successful survival. Thus, the second experiments were conducted in Andong from December 2007 to early March 2008. N. californicus conditioned in a greenhouse with natural day length was individually put in a small tube, and the tubes were kept under different ground surface conditions: bare, fallen leaves and urethane foam. When water had been added in the tube, the mites on bare ground had died after one month, while 70% of the mites of the other cover treatments were surviving. In these cover treatments, 7-10% of the mites had survived until two months, and eventually all died within three months. This result showed that hiding under cover structure near ground surface may be effective to increase winter survival of N. californicus. Therefore, collecting weeds which have rosette leaves may be an effective method to estimate of the overwintering possibility of N. californicus in the Korean mainland.