Although understanding dispersal ecology is important of Haemaphysalis longiconirs (Acari: Ixodidae) to control severe fever with thrombocytopenia syndrome, the small size of H. longicornis makes it challenging to study their behaviors. We examined the potential of fluorescent marking system (FMS) paired with an ultraviolet laser, an effective insect detection method, in tracking of H. longicornis. When we assessed potential effects of FMS on the survivorship and behavioral parameters including horizontal movement, vertical climbing height, and response to CO₂ of all development stages (larva, nymph, and adult) of H. longicornis, it did not induce any adverse effects on the hard ticks. Furthermore, we measured the detectable distance and detection rate of larvae, nymphs and adults to evaluate the detection efficacy of FMS. Using an ultraviolet laser, operators could detect the hard ticks from a distance ranging from 12 m (larva) to 29 m (adult). When the detection rate was measured in a grassland both during day and night, it was higher at night compared to day and increased with the body size. The detection rate was over 90% for all stages of the hard ticks at night, whereas larvae and nymphs showed that of 23% and 34% respectively during the day. However, the detection rate of adults was higher compared to other development stages regardless of time of experiment. Our results indicate that FMS can serve as a promising tool to track the hard ticks by providing reliable detection efficacy with no adverse effects on the marked individuals.

In general, hemipteran insects transmit either obligate or facultative symbionts to their offspring using various transmission mechanisms. Riptortus pedestris (Hemiptera: Alydidae) also have facultative symbiosis with Burkholderia sp. which is acquired from the soil every generation especially during 2nd instar nymphal period. This environmental symbiont transmission makes R. pedestris face a great risk of missing their symbionts, however, previous studies showed that they have intimate associations with their symbionts. Therefore, we suspected that R. pedestris 2nd instar nymphs may have a preference toward Burkholderia sp. to achieve an efficient symbiont acquisition during the limited time of window. In order to identify the preference of 2nd instar nymph, we first conducted dual-choice experiments varying with the number of 2nd instar nymphs (a nymph and 100 nymphs) in plastic cages. Furthermore, Y-tube olfactometer experiments varying with the presence of soil as medium of Burkholderia sp. were performed to determine if the insects respond to bacterial volatile induced from the symbiont. Based on our results, we observed that R. pedestris 2nd instar nymphs may not show any specific behavioral preference or response to chemical volatile from Burkholderia sp. in laboratory conditions (P >0.24). Therefore, we will further conduct a dual-choice experiment in a semi-field condition to investigate if such patterns can be detected in a larger arena simulating a more natural environment.

Both a fluorescent marking system (FMS) and a portable harmonic radar system (PHRS) are effective insect tracking methods. Prior to comparing their efficacies, we tested the viability of FMS in detection of an agricultural pest, Riptortus pedestris (Hemiptera: Alydidae); previous studies showed the harmlessness of PHRS on R. pedestris and its detection distance. Fluorescent marking allowed the detection of marked R. pedestris from > 25 m, when illuminated with a laser in the dark, while affecting only the vertical walking distance of the insect. Then, we assessed the efficacy of the FMS and PHRS as well as combining both methods (BOTH) in detection of R. pedestris in a grass field and a bean field during day and night. PHRS and BOTH showed higher detection rates than FMS in all settings, except for in the bean field at night. Also, although BOTH did not enhance total detection time, it facilitated the retrieval of the sample at night compared to only using PHRS.

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 (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.

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.