Haemaphysalis longicornis (Acari: Ixodidae) is a medically important arthropod vector of tick-borne diseases, especially the severe fever with thrombocytopenia syndrome (SFTS). To establish a management strategy against tick-borne diseases, it is fundamental to understand the basic biology of vector species. Therefore under laboratory conditions, we evaluated the horizontal movement of adult and nymph stages of H. longicornis to better understand their dispersal behaviors. In the experiments, field populations were subjected to video recording of the horizontal movement of the ticks in a petri-dish arena for 3 hours. Our results indicate that nymphs showed a significantly higher mobility than adults, whereas there was no significant difference in angular velocity. Nymphs moved 3.74 ± 0.26 m at an angular velocity (AV) of 1.60 ± 0.07 deg/s. and adults moved 2.91 ± 0.26 m at an AV of 1.61 ± 0.14 deg/s.

Seasonal distribution of disease vector species including mosquitoes and ticks plays a key role in establishing risk managementof vector-borne disease. However, environmental factors affecting abundance and distribution of vector species are notcurrently well understood. Therefore, we conducted a two-year field sampling to address the population dynamics of mosquitoesand ticks in Gyeonggi-do in 2015 and 2016. In 2015, the population density was highest in May for ticks (e.g. Haemaphysalislongicornis) and June for mosquitoes (e.g. Aedes vexans), whereas both pest groups peaked in August in 2016. Culexpipens (82.3% Species Ratio), Ae. vexans (77.3% SR), and Anopheles sinesis sp. (45.3% SR) were the most dominantspecies in urban area, cow shed and wild bird refuge, respectively. For ticks, H. longicornis (47.7% SR) was the mostdominant throughout four potential habitats.

Different types of insect-borne plant viruses can modify their hosts and vectors in distinct manners. Therefore, interactionsbetween two types of viruses co-existing in a field are known to be complex to predict. Obtaining empirical data byconducting field experiments, however, requires numerous biotic and abiotic factors to be controlled, and is therefore hardto execute. Thus, we designed an individual based model to simulate the transmission pattern of two viruses, using potatoes(Solanum tuberosum) for host plant, aphids (Myzus persicae) for virus vector, potato leafroll virus and potato virus Yfor different types of plant viruses. More specifically, we aimed to investigate the effect of the following on the spreadof the plant viruses: dispersal by winged-form aphids, initial number of virus-infected seed potatoes, and indirect interactionsbetween two viruses by affecting life traits of the vectors.

Vertical transmission of symbiont is known as the most effective way to deliver their offspring. However, it has beenreported that the bean bug, Riptortus pedestris, acquires its gut symbiont, Burkholderia sp., from its environment (e.g.soil) during the 2nd instar nymphal stage. Nevertheless, it is not unknown how they locate their symbiont. For this reason,dual-choice experiments were conducted in both solitary (a nymph) and group conditions (100 nymphs) to investigatewhether or not R. pedestris has preference on Burkholderia sp. treated or untreated solution in laboratory conditions. Inthese experiments, there was no significant difference in the preference between the two treatments. We are testing inthe Y-tube olfactometer system to evaluate the response of R. pedestris on possible chemical cues from Burkholderia sp..

The bean bug, Riptortus pedestris, is a pest of leguminous crops. Recent studies have revealed an interesting relationship between R. pedestris and a gut symbiont Burkholderia sp.. R. pedestris mainly acquires Burkholderia sp. during 2nd instar period, which leads to enhancement of growth and reproductive rate of the host. Nevertheless, how R. pedestris acquires its symbiont is not yet clearly described. Therefore, we investigated whether 2nd instar nymphs have preference on Burkholderia sp. compared to untreated control in laboratory settings. In the choice test, no significant difference was found in the preference by R. pedestris between the two treatments. To further investigate single individual’s behaviors (its first choice, approaching frequency to each treatment, and residence time on the treatment). We video-recorded single individuals in the choice setting for 12 hours. Again, there was no significant difference in any of the behavioral traits recorded. Further choice tests will be conducted in the Y-tube olfactometer systems and semi-field conditions.

The bean bug, Riptortus pedestris (Hemiptera: Alydidae), is one of the major pests on leguminous crops especially in Korea and Japan. Because of its economic importance as crop pest, A large proportion of research on this species have focused on applied questions related to pest management tactics. In addition to the applied research, recent studies have also revealed an interesting relationship between R. pedestris and a gut symbiont Burkholderia sp. as an ideal model system for insect-microbe symbiotic interaction. Under this circumstance, our research group initiated a series of research projects to better understand behavioral ecology of R. pedestris and address its implications for both basic and applied questions. This presentation will cover various behavioral studies with R. pedestris including sublethal effects of insecticides, harmonic radar tracking, overwintering ecology, and symbiont acquisition mechanisms

Plant virus can enhance its transmission by altering the settling preference of its vector. Nevertheless, most of the studies have focused on the spread of one virus in a field whereas often times there are more than single virus infecting same crop. Furthermore, mixed-infection of multiple viruses tends to cause more severe virus symptoms and changes vector’s biology and behavior different than singular infection. Thus, we are currently investigating the spatial transmission pattern of persistently transmitted potato leafroll virus and non-persistently transmitted potato virus y. However, due to impracticability of obtaining empirical data, we are programming an individual-based modelling software while taking biology of potato, biology and behavior of aphid and different characteristics of two viruses into consideration.

Insects are extremely abundant and diverse. Their ecological importance may outweigh that of other animal groups in both natural and managed ecosystems. To foster beneficial roles of insects while reducing their adverse effects, it is crucial to understand insect behaviors and address its implications for applied ecological questions. Therefore, my research group has focused on studying behavioral ecology of several economically important pests including whiteflies, stink bugs, bean bugs, mosquitoes, and ticks. In this talk, I will present classical and new techniques to study behaviors of the insects and some of the important findings, especially about dispersal and overwintering ecologies.

An insect is a ectothermal animal that is vulnerable to the temperature change. As climate change accelerated, the distribution of insects have been rapidly changed. Rice is the most important crop in Korea as it is a staple for Korean people. In the rice paddy, migratory pests from south-east Asia have seriously damaged on the crop. As climate changed, the spatial distribution of pest and their effects on rice paddy may be changed. Therefore, monitoring the pest populations is a basis for establishing further research for pest management strategy against these migratory insect pests. As the first year for this monitoring project, we set 20 rice paddies in Gyeonggi-do and Chungcheongnam-do as continuous monitoring sites for five major migratory pests and summarized the first year’s data. Based on it, we will develop better monitoring plan as well as analysis methods.

Mosquitoes and hard ticks are vectors of serious diseases, but factors affecting the abundance and distribution of vector species are not well-understood. Therefore, we monitored mosquito populations from three potential mosquito habitats using black light traps and BG-Sentinel traps in Gyeonggi-do, 2016. Also, we surveyed ticks using CO2-based traps at one location in Gyeonggi-do, 2016. From the traps, we collected a total of 4,818 mosquitoes in three potential mosquito habitats, and 3,207 ticks in Gyeonggi-do. Among the collected samples, the highest density of mosquitoes were observed in August, and tick density was highest in August either. In the samples, dominant mosquitoes were Aedes vexans nipponii (Species Ratio 49%), and Culex pipens pallens (SR 25%) in mosquito habitats and dominant ticks were Haemaphysalis longicornis (SR 56%) in Gyeonggi-do. This monitoring program for vector species can help develop effective management strategy, especially under the global climate change.

It is not uncommon in the nature for insects to have symbiotic relationships with microorganisms. The bean bug, Riptortus pedestris, which harbors symbiont Burkholderia sp., is a serious agricultural pest in South Korea and Japan. It is reported that the symbiont has positive effects on the fitness of R. pedestris. However, virtually no information is available for how this insect finds the symbiont in the nature and how the behavior of R. pedestris is affected by the symbiont. To investigate the symbiont acquisition mechanism, the frequencies of R. pedestris approaching to symbiont or untreated control treatment were compared in a plastic cage (465×290×260mm) (n=20). In the experiment, there was no detectable difference between the two treatments. Further study using video tracking systems will help us to better understand detailed behaviors for symbiont acquisition.

The bean bug, Riptortus pedestris (Hemiptera: Alydidae), is a major pest of soybean and tree fruit in Korea. To protect crops, chemical insecticides have been widely used. However, the effects of insecticides is not only reduce the pest population but also change of pest behavior. In this study, we tested the effects of two insecticides, etofenprox (pyrethroid) and acetamiprid (neonicotinoid), on the behavior of R. pedestris. Two insecticides were diluted with water based on the conventional spray dose. After exposed to insecticide residue, adult R. pedestris was put individually into a clean petri dish with soybean. The behavior of R. pedestris was video-recorded for 16 hours. The frequencies of approaching to food and feeding were compared to the untreated control group. R. pedestris exposed to etofenprox made more frequent approaching to the food, but those exposed to acetamiprid made less frequent approaching compared to the control group. When compared to the control group, the feeding frequency of acetamiprid-exposed group was significantly reduced but etofenprox-exposed group showed more frequent feeding activity. In both treatments, the feeding probability, calculated by feeding frequency divided by approaching frequency, was reduced compared to the control. We conclude that acetamiprid may protect crops by reducing the frequency of R. pedestris to approach and feed on crops.

Seasonal abundance and distribution of mosquitoes and chigger mites are important for human populations. However, factors affecting the abundance and distribution of vector species are not well - understood. Furthermore, global climate change makes it difficult to predict the population dynamics of vector species. Therefore, it is important to monitor this vector species over a long period of time. In 2015, mosquitoes were collected from three potential mosquito habitats using black light trap and BG-Sentinel trap in Gyeongi-do in April through October. Also, we collected chigger mite using sherman live traps in Cheorwon, Gangwon-do in April, September and October. From the survey, we collected a total of 11,649 mosquitoes in three potential mosquito habitats, and a total of 3,656 chigger mites from 54 wild rodents. In the samples, dominant mosquito species were Aedes vexans nipponii (Species Ratio 70%), Culex pipens pallens (SR 9.8%) in Gyeonggi area and dominant chigger mite species was Leptotrombidium pallidium (SR 59%) in Cheorwon. The results of this study can serve as provide fundamental basis to develop effective management strategy under the global climate change environment.

Various techniques have been developed to monitor insect behavior in the field. Harmonic radar tagging is a promising method of tracking target insects because it can allow efficient detection of the insects with negligible effects on their behavior or physiology. However, availability of the light limits the effectiveness of the method as it is almost impossible to spot an insect in the dark. On the other hand, fluorescent-marking, when combined with strong light source, makes the organisms distinct at night in a non-destructive manner. Therefore, we conducted a field experiment to determine the effectiveness of the combination of the two methods. Riptortus pedestris (Fabricius) adults were marked with both harmonic radars and fluorescent paint. The marked insects were haphazardly arranged and pinned onto trees or the ground in the forest at night. Then, a group of paired researchers, one equipped with a harmonic radar and the other with a hand-held laser, attempted to find R. pedestris within 20 minutes. The detection rate showed a high variance ranging from 40% to 100%. Thus, with a proper training, harmonic radar system combined with fluorescent-marking can be a powerful technique to detect insects in the field. With these equipments, tracking insect behavior in the field will be more efficient in the dark.

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.

Whiteflies (Hemiptera: Aleyrodidae) and thrips (Thysanoptera: Thripidae) are major pests on greenhouse crops including sweet pepper (Capsicum annuum L.) in South Korea. To manage this pest complex effectively, it is fundamental to understand population dynamics and spatial distributions of the pests. In this study, we conducted visual counting and used yellow sticky traps to monitor whitefly and thrips populations in sweet pepper greenhouse (6 × 28 m). The survey was conducted every two weeks over two months. A total of 84 traps were set up at 20cm from the plant top canopy and spaced 1m apart from each other. Leaves were selected randomly from the middle plant canopy for visual counting at the same sampling locations. The trap data indicate that the numbers of whiteflies and thrips increased from 5.50 ± 0.34 to 168.51 ± 14.95 and from 52.40 ± 1.67 to 158.42 ± 7.44 (mean ± SE) per trap, respectively, over the two-month observation period. In general, the spatial distributions of these pests aggregated near the greenhouse entrance with significant positive correlation between the densities of the two species (r = 0.74, P = 0.02). However, the results of visual counting were completely different; either species was rarely found on leaves, even when the trap catches were relatively high at the same locations. That is, there was no correlation between visual counting and sticky trap data sets. The current study will serve as a fundamental step to develop reliable and effective management programs for greenhouse sweet pepper.

Sweet pepper (Capsicum annuum L.) is one of the leading export greenhouse crops in South Korea. Sweetpotato whitefly, Bemisia tabaci Gennadius is one of the major pests on greenhouse pepper. This pest is conventionally managed by synthetic insecticide application, however this management tactic causes the overuse of toxic compounds and the resistance of whiteflies to insecticides. Therefore, the development of environment-friendly natural insecticides is vitally important. In this study, we evaluated the efficacy of three newly-screened insecticidal compounds for B. tabaci (Biotype Q) in laboratory. The insecticidal effects of the compounds were assessed with adult B. tabaci using leaf disc arena established in petri dish. Among the three compounds tested, JS408, a plant extract from Perilla sp., showed significant insecticidal effects on B. tabaci in one hour causing 90% mortality. However, JA408 caused phytotoxicity on sweet pepper leaf resulting in browning dead spots. The new plant-extract JA408 has promising potential as natural insecticidal compound for B. tabaci, but further study must resolve the phytotoxicity issue. Moreover, insecticidal effect should be evaluated under field conditions.

Mosquitoes are vectors of many human diseases such as Japanese encephalitis, vivax malaria, west nile fever, dengue fever and yellow fever. However, factors affecting the abundance and distribution of mosquitoes are not well-understood. Moreover, the global climate change makes it even more difficult to address and predict the population dynamics of mosquitoes. Therefore, it is important to monitor this medically-important pest throughout landscapes over a long period of time. This study was conducted as a part of the nation-wide surveillance program to monitor insect vectors. In 2015, mosquitoes were collected using black light traps and BG-Sentinel traps in Gyeonggi-do at every two weeks from April to September. Three types of potential mosquito habitats were selected for surveillance: urban area (Suwon), cattle shed (Yongin) and wild bird refuge (Gwangju). Among the three habitats, female mosquitoes were first caught on April 4 by BG-Sentinel trap in the urban area. The highest density of female mosquitoes in the traps was recorded in July in the urban area (134 ± 84 per trap); the highest density was observed in June in the cattle shed (2473 ± 1319) and wild bird refuge (21 ± 15) (mean ± SE). The dominant mosquito species were Culex pipens pallens (91%), Aedes vexans nipponii (79%) and Anopheles sinensis (33%) in the urban area, cattle shed and wild bird refuge, respectively. The results of this study indicate that female mosquitoes were most abundant in the cattle shed habitat type. It is also noteworthy that the dominant mosquito species varied among the habitat types surveyed. This nation-wide monitoring program for medical pests will provide fundamental basis to develop effective management strategy under the global climate change environment.

An invasive pest is a non-native species which can cause damage to the economy, natural resources, or human health. The invasion of these non-native species is an escalating problem worldwide. In particular, it is estimated that ca. 50,000 nonindigenous species have been introduced into the United States, many of which have caused a total of > $100 billion losses in natural and agricultural ecosystems. Recently, two invasive pests, Halyomorpha halys (Hemiptera: Pentatomidae) and Drosophila suzukii (Diptera: Drosophilidae), have emerged as serious agricultural pests in the U.S. Both species are native to Asia, however the distributions of the pests have rapidly expanded across the U.S. causing significant economic losses especially in specialty crops, presumably due to similarities in host plant complex and climatic environments between the native and new regions. In this study, a series of research efforts to protect agriculture and the environment against H. halys and D. suzukii in the U.S. are summarized and reviewed.

Currently, the management of Riptortus pedestris (Hemiptera: Alydidae) relies mainly on insecticide application in most crop productions. However, there have been very few detailed studies concerning the potential behavioral effects of sublethal dose of insecticide. This study was conducted to address sublethal effects of five insecticides on the mobility of R. pedestris. Adult R. pedestris were individually exposed to dry residue of insecticides for 4 hours in laboratory. Tested insecticides were fenitrothion (organophosphate), etofenprox (pyrethroid), bifenthrin (pyrethroid), acetamiprid (neonicotinoid) and dinotefuran (neonicotinoid). After the exposure, vertical climbing ability and flight capacity of survived R. pedestris were evaluated and compared to water-treated control. First, the mortality of R. pedestris after the 4-h insecticide exposure was as follows: 10% for fenitrothion, 3.4% for dinotefuran, 3.4% for acetamiprid, 0% for etofenprox and 0% for bifenthrin. The vertical mobility of R. pedestris was affected differently by insecticides tested. Acetamiprid resulted in decrease (37%) in the vertical mobility, whereas dinotefuran caused increase (153%) in the ability compared to the control. There was no effect by three other insecticides on the vertical mobility. In general, tested insecticides did not affect the flight capacity of R. pedestris compared to untreated individuals. However, etofenprox resulted in increase (230%) in the flight capacity. The results of this study indicate that insecticide-treated but survived R. pedestris can show similar or even increased mobility compared to untreated individuals. This should be considered in designing insecticide application programs against of R. pedestris.