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.

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.

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.

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.