Riptortus Clavatus Research Articles

Novel Fungal Species Belonging to the Genus Acaulium Isolated from Riptortus clavatus (Heteroptera: Alydidae) in Korea

Novel Fungal Species Belonging to the Genus Acaulium Isolated from Riptortus clavatus (Heteroptera: Alydidae) in Korea

Susceptibility of Myzus persicae on Potato field and Riptortus clavatus on Soybean field to Insecticides treated by Multi-copter

Susceptibility of Myzus persicae on Potato field and Riptortus clavatus on Soybean field to Insecticides treated by Multi-copter

Behavioral and Electrophysiological Effects of Ajowan (Trachyspermum ammi Sprague) (Apiales: Apiaceae) Essential Oil and Its Constituents on Nymphal and Adult Bean Bugs, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae).

We investigated the repellent effect of 12 Apiaceae plant essential oils on nymphal and adult (male and female) forms of the bean bug, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae), using a four-arm olfactometer. Among the essential oils tested, ajowan (Trachyspermum ammi Sprague) essential oil showed the strongest repellent activity against the nymphal and adult bean bugs. For female adults, the repellent activity was significantly different between an ajowan oil-treated chamber and an untreated chamber down to a concentration of 14.15 μg/cm2. We also investigated the repellent activity of individual ajowan essential oil constituents. Of the compounds examined, carvacrol and thymol showed the most potent repellent activity against the nymphal and adult bean bugs. Carvacrol and thymol exhibited 73.08% and 70.0% repellent activity for the bean bug nymph at 0.71 and 2.83 μg/cm2, respectively, and 82.6% and 80.7% at 5.66 and 11.32 μg/cm2, respectively, for male adults. Carvacrol and thymol exhibited strong repellent activity against female adult bean bugs down to a concentration of 2.83 μg/cm2. Ajowan essential oil, thymol and carvacrol elicited a negative electroantennogram (EAG) response from adult bean bugs. This could explain the repellent activity of ajowan essential oil and its constituents. Our results indicate that ajowan essential oil and its constituents carvacrol and thymol can be potential candidates as the ‘push’ component in a ‘push-pull’ strategy for bean bug control.

식물병원성 곰팡이에 대한 곤충장내세균의 항균활성

In order to investigating the effects of antifungal activity of intestinal bacteria obtained from insect, it was identified these bacteria isolated from the gut. In this result, total 49 isolates of intestinal bacteria were identified from 10 kinds of insect species. It was that 4 isolates including Cedecea sp. from Nesidiocoris tenuis, 3 isolates including Enterobacter sp. from Odontotaenius disjunctus, 4 isolates including Acinetobacter sp. from Reticulitermes speratus, 4 isolates including Clavibacter sp. from Riptortus clavatus, 11 isolates including Bacillus sp. from Lema decempunctata, 3 isolates including Enterococcus sp. from Henosepilachna vigintioctopunctata 2 isolates including Staphylococccus sp. from Harmonia axyridis, 5 isolates including Enterobacter asburiae from Popillia mutans, 7 isolates including Aeromonas sp. from Hydrophilus acuminatus, and 7 isolates including Brucella sp. from Anomala octiescostata. In order to investigating antifungal activity against plant-pathogenic fungi, Altanaria solani, Colletotrichum gloeosporioides, Botrytis cinerea, Fusarium oxysporum, Phytophthora capsici, Rhizoctonia solani and Selerotinia sclerotiorum were dual cultured with each 49 gut enterobacteriaceae. As these results showed that many isolates have the antifungal activities including 26 isolates against A. solani, 6 isolates against B. cinerea, 13 isolates against C. gloeosporioides, 11 isolates against F. oxysporum, 17 isolates P. capsici, 2 isolates against R. solani and 2 isolates against S. sclerotiorum. Pseudomonas aeruginosa was showed strong antifungal activity against all of tested plant pathogens. It might be taken a potential for application against plant-pathogenic fungi with useful control agent.

Inheritance and Quantitative Trait Loci Analysis of Resistance Genes to Bruchid and Bean Bug in Mungbean (Vigna radiata L. Wilczek)

Bruchid (Callosobruchus chinenesis L.) and pod sucking bug (Riptortus clavatus Thunberg) are serious insect pests during the reproduction stage and seed storage period of legume crops worldwide. However, few sources of resistance to each of these insects have been identified and characterized, and no genetic studies have been carried out with simultaneous tests of these two insects. In this study, the inheritance of seed resistance to Callosobruchus chinenesis L. and Riptortus clavatus Thunberg was examined in a mungbean cultivar, Jangan mungbean, which was developed by backcrossing with the V2709 resistant donor. The F1, F2, and F3 seed generations were developed from the cross between susceptible and resistant parents, and evaluated for resistance to the two insects. It was found that resistance to bruchid and bean bug was controlled by a single dominant gene in the F1 and F2 seeds. However, the segregation pattern of reciprocal reaction to each insect in F2 seeds showed seeds were susceptible to each insect. These results suggest that the resistance genes in Jangan mungbean to bug and weevil are either different or closely linked with each other. A genetic linkage map 13.7 cM in length with 6 markers was successfully constructed. Two QTLs were identified for bruchid resistance, and a QTL for bean bug resistance was detected. One of the QTLs for resistance to bruchid was shared with the QTL for bean bug. These newly developed closely linked markers will be used for cloning of the resistance genes to bruchid and bean bug in the future.

Heterologous Expression of Corn Cystatin in Soybean and Effect on Growth of the Stink Bug

The bean bug (Riptortus clavatus) is a serious insect pest of soybean. Corn (maize) cystatin strongly inhibited the activity of its digestive cysteine proteinase. Heterologous expression of corn cystatin in soybean seeds inhibited the insect's proteases, but not its growth.

Effect of Host–feeding on Reproduction in Ooencyrtus nezarae (Ishii) (Hymenoptera: Encyrtidae), an Egg Parasitoid of the Bean Bug Riptortus clavatus

Adult of many parasitoid species, in particular females, feed on host and non–host foods (e.g., sugar sources) for reproduction and maintenance (Lewis et al., 1998; Jervis et al., 1993; Jervis and Kidd, 1996; Onagbola et al., 2007). Feeding on host material such as host haemolymph is referred as to host–feeding. Host feeding is very common among adult females of synovigenic parasitoids that produce yolk–rich eggs throughout their lifetime, and has been observed for over 140 species across 17 families of Hymenoptera (Jervis and Kidd, 1986) and for several species of parasitic Diptera (Nettles, 1987). Female parasitoids, through host feeding, can gain nutrients that are used to mature eggs (Jervis and Kidd, 1986; Heimpel and Collier, 1996). Although sugar feeding has been demonstrated to increase the longevity of adult parasitoids in the majority of parasitoid species examined (e.g., Jervis et al., 1993; Fadamiro and Chen, 2005; Fadamiro et al., 2005), some studies have suggested that host meal or haemolymph may be a good source of nutrients for parasitoid survival and fecundity than sugars (Jervis and Kidd, 1986; van Lenteren et al., 1987; Heimpel and Collier, 1996). Although feeding on hosts is essential to maximizing female’s fecundity, its contribution to reproduction varies from species to species (Sandlan, 1979; Collier, 1995a; Rivero and Casas, 1999; Ueno, 1999; Rivero et al., 2001; Ueno and Ueno, 2007). Jervis and Kidd (1986) divided host feeding in terms of its concurrency and destructiveness: concurrent or non–concurrent, and destructive or non–destructive. Concurrent feeding means that female parasitoids use the same host individual for both feeding and oviposition, while non–concurrent means that different hosts are used for the different purposes. Destructive host feeing means that hosts die or heavily damaged upon host feeding, while in the case of non–destructive host feeding, hosts survive or are not damaged. Most evidence implies that host feeding in egg parasitoids always occurs on hosts that are also used for oviposition (Jervis and Kidd, 1986; Takasu and Hirose, 1993). For egg parasitoids, hosts may be important for maximizing both egg production and longevity. Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) is an egg parasitoid wasp of several phytophagus Hemiptera including the bean bug, Riptortus clavatus Thunberg (Takasu and Hirose, 1985, 1986; Effect of Host–feeding on Reproduction in Ooencyrtus nezarae (Ishii) (Hymenoptera: Encyrtidae), an Egg Parasitoid of the Bean Bug Riptortus clavatus

Effect of Host Density on the Progeny Production of the Egg Parasitoids Ooencyrtus nezarae (Ishii) (Hymenoptera : Encyrtidae)

The effects of host density on progeny production, clutch size and sex ratio of Ooencyrtus nezarae, an egg parasitoid of the bean bug Riptortus clavatus, were examined to determine the optimal host provision condition in which mass-rearing efficiency of the parasitoid is maximized. Female parasitoids allocated prog- eny in regard to host density so as to avoid laying more eggs than the host can support. The maximum prog- eny production and parasitism rate occurred when 5 host eggs were given everyday throughout the life time. However, if we continuously provided with hosts for ten consecutive days, the progeny production with one host per day was more consistent than that with five hosts per day. Female O. nezarae reduced the clutch size if the host density was beyond five. However, the overall progeny sex ratio remained constant regardless of the host density. The results suggested that the excessive exposure of the host to O. nezarae wouldn't affect the reproductive fitness, but would reduce the reproductive potential of this parasitoid, which can in turn affect the efficiency of mass rearing perspective.

곤충병원세균(Xenorhabdus nematophila) 유래물질의 톱다리개미허리노린재(Riptortus clavatus) 장내세균 증식억제 및 살충효과

톱다리개미허리노린재(Riptortus clavatus)의 장내세균이 분리되었다. 형태학적 분석과 생화학적 분석을 통하여 세균이 Staphylococcus succinus와 가장 유사한 것으로 동정되었다. 16S rRNA 유전자의 염기서열은 이러한 동정 결과를 뒷받침했다. 페니실린G를 톱다리개미허리노린재 성충에게 경구투여 하였을 때 장내세균 밀도 감소와 치사 효과를 유발하였다. 동일한 방법으로 곤충병원세균(Xenorhabdus nematophila)의 세 가지 대사물질(benzylideneacetone, proline-tyrosine, and acetylated phenylalanine-glycine-valine)을 처리하였을 때, 톱다리개미허리노린재 장내세균의 밀도감소와 치사효과를 확인하였다. 이러한 결과는 톱다리개미허리노린재의 장내세균이 Staphylococcus sp.이며, 곤충병원세균 대사물질의 항균 활성이 장내세균과 궁극적으로 톱다리개미허리노린재의 생존에 영향을 미친다는 것을 제시하였다. A bacterial colony was isolated from the gut of the bean bug, Riptortus clavatus. From morphological and biochemical tests, the bacterial isolate showed the highest similarity to Staphylococcus succinus. DNA sequence of 16S rRNA gene of the bacterium supported the identification. Oral administration of penicillin G to adults of R. clavatus gave a dose-dependent mortality of adults of R. clavatus to adults along with significant decrease of the bacterial population in the gut. Similarly, three metabolites (benzylideneacetone, proline-tyrosine, and acetylated phenylalanine-glycine-valine) derived from an entomopathogenic bacterium, Xenorhabdus nematophila, also inhibited growth of the gut bacterial population and gave significant mortalities to R. clavatus. These results suggest that a gut bacterial population classified as Staphylococcus sp. is required for survival of R. clavatus and that the three bacterial metabolites had toxic effects on the bugs due to their antibacterial properties.

톱다리개미허리노린재 암컷 성충의 휴면종료에 미치는 일장과 온도의 영향

한국, 일본을 비롯하여 아시아 대륙에 널리 분포하는 톱다리개미허리노린재 (Riptortus pedestris (Fabricius)) (Hemiptera: Alydidae)는 겨울에 성충으로 휴면한다. 2006년 10월~11월 사이에 야외에서 월동 중인 암컷 성충을 대상으로 휴면종료에 미치는 온도와 일장 및 그 처리기간의 영향을 연구하였다. 암컷을 해부하여 난소 발육 정도를 기준으로 휴면 종료 여부를 판정하였다. 처리 방법은 (1) 고온장일: <TEX>$25^{\circ}C$</TEX>, 14L:10D 조건에 1, 2, 3주 또는 30일간 처리, (2) 고온단일: <TEX>$25^{\circ}C$</TEX>, 10L:14D 조건에 1, 2, 3주 처리, (3) 저온장일: <TEX>$8^{\circ}C$</TEX>, 14L:10D에 1, 2, 3주 처리 후 고온장일에 3주간 처리, (4) 저온단일: <TEX>$8^{\circ}C$</TEX>, 10L:14D에 1, 2, 3 주간 처리 후 고온장일에 3주간 처리이었다. 고온단일처리는 난소발육에 영향을 미치지 않았고, 결과적으로 포란수나 휴면종료율이 무처리(실험 전의 성충)와 차이가 없었다. 그러나 고온장일처리는 고온단일처리보다 휴면종료 비율이 높았다. 고온 장일에 14일 이상 처리하면 휴면종료 암컷의 비율이 증가하고 난소발육이 촉진되었으며, 난소 내의 성숙난의 수도 증가하였다. 고온장일이나 고온단일 처리와 비교하였을 때, 저온장일이나 저온단일 처리 후 고온장일 처리는 난소발육을 촉진하였고 산란 성충수가 증가하였다. 저온단일에 일주일 간 전처리가 산란수 증가에 충분하였다. The bean bug, Riptortus clavatus Thunberg (Hemiptera: Alydidae), is a pest of soybeans and tree fruits. It enters reproductive diapause during winter. We studied the effect of different combinations of temperature, day length, and treatment period on the termination of diapause in R. clavatus using adult females collected in October and November 2006. Ovarian development was used to determine diapause termination. The treatments were: (1) HTLD; <TEX>$25^{\circ}C$</TEX>, 14L:10D treatment for 1, 2, 3 weeks and 30 days, (2) HTSD; <TEX>$25^{\circ}C$</TEX>, 10L:14D treatment for 1, 2, and 3 weeks, (3) LTLD; <TEX>$8^{\circ}C$</TEX>, 14L:10D treatment for 1, 2, and 3 weeks followed by HTLD for 3 weeks, and (4) LTSD; <TEX>$8^{\circ}C$</TEX>, 10L:14D treatment for 1, 2, and 3 weeks followed by HTLD for 3 weeks. The HTSD treatments did not affect ovarian development, and resulted in no significant difference in the number of mature eggs in ovaries or the percentage of diapause-terminated females compared to the control females before treatment. The percentage of females that terminated diapause was significantly higher in the HTLD treatment than in the HTSD treatment. The HTLD treatment for more than 14 days increased the percentage of diapause-terminated females, accelerated the development of the ovaries, and increased the number of mature eggs in ovaries. Compared with the HTLD or HTSD treatments, the LTLD or LTSD treatments followed by the HTLD treatment accelerated ovarian development and increased the number of ovipositing females. The pre-LTSD treatment for 1 week was enough to increase the number of eggs oviposited.

노린재류 접종시기와 밀도에 따른 단감 피해과율

단감에 피해를 일으키는 노린재의 피해양상을 밝히기 위해 접종시기별, 접종밀도별 피해과율을 조사하였다. 톱다리개미허리노린재에 의한 피해과율은 접종밀도, 접종시기, 먹이조건에 따라 유의하게 차이가 있었으며 결과모지당 5마리 접종구에서부터 피해를 보이며 접종시기에서는 6월, 7월, 8월에는 피해가 적었으며 9월, 10월에 피해과가 많아졌다. 단감을 단일먹이로 한 것과 강낭콩과물을 제공한 먹이조건에서의 피해과율에서 유의하게 차이가 있었다. 톱다리개미허리노린재에 의한 피해과는 흡즙흔적이 있는 식흔과로 남으며 흡즙에 의한 낙과증상은 없었다. 썩덩나무노린재는 7월, 8월, 9월의 접종시기별 피해과율이 유의하게 차이가 있었으며 접종밀도에 따른 피해과율에 유의하게 차이가 있어 5마리 처리구에서는 7월의 경우 100%의 피해과율을 보였다. 갈색날개노린재의 접종시기에 따른 피해과율은 유의한 차이가 없었고 접종수준에 따른 피해과율은 1마리, 3마리, 5마리에서 각각 유의하게 차이가 있었다. 피해증상으로 톱다리개미허리노린재와 달리 7월, 8월에는 피해를 받은 과일이 대부분 낙과되었으나 9월 이후의 피해과는 낙과되지 않고 식흔과가 많았다. This study was conducted to investigate the fruit damage according to the number of released stink bugs and date of adult introduced on non-astringent persimmon. The fruit damage differed significantly by the number, date, and the source of feed for Riptortus clavatus. Damages on the fruits appeared when five bugs were released to mother branches bearing fruits. Damages to the fruits was heavy in the case that bugs were introduced in September and October, compared with in June, July and August. Persimmon fruit damage was influenced significantly by the available sources to R. clavatus, persimmon fruit alone or additional supply of kidney bean (Phaseolus vulgaris) and water. Characteristic damage symptoms by R. clavatus showed only scars on the fruit skin, without fruit dropping. Halyomorpha halys (=mista) showed significantly higher fruit damage when they were released in July, August, and September compared with other periods. Number of H. halys to the fruit also showed significant differences in fruit damages. Five H. halys in July showed 100% damaged fruits. The fruit damage by Plautia stali was not significantly different according to dates of introduction but the number of insects gave significant differences in the fruit damage ratio at the level of 1, 3, 5 bugs introduced to the mother branche bearing friuts. The damage symptoms by P. stali was fruit dropping in July and August but from September damaged fruits were found in the branches.

Repellency and Electrophysiological Response of Caraway and Clove Bud Oils against Bean Bug Riptortus clavatus

This study was performed to investigate the repellent activity of thirteen plant essential oils and to confirm their electrophysiological response against the bean bug Riptortus clavatus. Among the tested oils, caraway (100%) and clove bud oil (92%) significantly repelled the bean bugs at a dose of 0.142 μL/cm2 by using an olfactometer. GC-MS analysis revealed that the active components responsible for the effective repellency of caraway and clove bud oil were carvone (56%) and limonene (44%); eugenol (81%), isoeugenol (12%) and β-caryophyllene (7%), respectively. Of the different active constitutions, eugenol was the most significant one than the others with reference to repellent activity against the bean bugs. Analysis by GC-EAD showed, major components of two essential oils that elicited responses in R. clavatus antennae, indicating the potential role of the essential oils as repellents that determine the choice of the repellent material.

장안녹두가 노린재류의 약충발육, 성충수명 및 산란에 미치는 영향

(태광콩, 경선녹두 및 장안녹두) 종실이 6종 노린재류의 약충발육, 성충수명 및 산란에 미치는 영향을 비교하였다. 태광콩에서 6종 노린재류의 약충은 모두 정상적으로 발육하였으며, 경선녹두와 장안녹두에서 톱다리개미허리노린재, 썩덩나무노린재 및 알락수염노린재의 약충은 정상적인 발육을 하였으나, 경선녹두에서 갈색날개노린재, 가로줄노린재 및 풀색노린재의 4령 약충 이후에 모두 사망하였고, 장안녹두에서는 3령 약충 이후 모두 사망하였다. 약충의 영기별 발육기간은 영기가 증가할수록 길었으며, 약충기간은 노린재의 종류에 관계없이 태광콩>경선녹두>장안녹두의 순으로 짧았다. 노린재류의 우화율은 태광콩에서 <TEX>$20{\sim}62%$</TEX>, 경선녹두에서 <TEX>$16{\sim}50%$</TEX>, 장안녹두에서 <TEX>$8{\sim}12%$</TEX>로 두류종실에 따라 차이가 있었다. 성충수명은 태광콩에서 수컷은 <TEX>$29.0{\sim}59.3$</TEX>일, 암컷은 <TEX>$29.7{\sim}54.4$</TEX>일, 경선녹두에서 수컷은 <TEX>$15.4{\sim}41.3$</TEX>일, 암컷은 <TEX>$14.3{\sim}43.3$</TEX>일, 장안녹두에서 수컷은 <TEX>$8.0{\sim}11.7$</TEX>일, 암컷은 <TEX>$5.5{\sim}11.0$</TEX>일로 노린재의 종류 및 기주에 따라 차이가 있었다. 산란전기간과 산란수도 태광콩에서 각각 <TEX>$5.1{\sim}8.3$</TEX>일 및 <TEX>$50.5{\sim}124.5$</TEX>개, 경선녹두에서 <TEX>$8.0{\sim}98.7$</TEX>일 및 <TEX>$16.4{\sim}55.2$</TEX>개로 노린재의 종류 및 기주에 따라 차이가 있었으며, 장안녹두를 먹고 자란 조사된 6종중 톱다리개미허리노린재, 썩덩나무노린재 및 알락수염노린재는 전혀 산란하지 못하였고, 갈색날개노린재, 가로줄노린재 및 풀색노린재는 성충으로 우화하지 못하였다. Nymphal development, adult longevity, and oviposition of six different species of stink bugs were compared on seeds of a soybean cultivar, Taekwangkong, and two mung bean cultivars, Kyungseonnogdu and Jangannogdu in the insect rearing room (<TEX>$28{\pm}2^{\circ}C$</TEX>, 16L:8D). Nymphs of six species of stink bugs normally developed on Taekwangkong seed. While nymphs of Riptortus clavatus, Halyomorpha halys, and Dolycoris baccarum developed on seeds of Kyungseonnogdu and Jangannogdu normally, all nymphs of Plautia stali, Piezodorus hybneri and Nezara antennata died after 4th instars on Kyungseonnogdu and after 3rd instars on Jangannogdu. Each instar period tended to be increased as nymphal stages were progressed. Nymphal period was shortest on Taekwangkong seed, followed by Kyungseonnogdu and Jangannogdu, irrelevant to stink bugs species. Emergence rate, adult longevity, and preoviposition period of 6 stink bugs were different depending on the reared seeds. Of 6 different species examined, Riptortus clavatus, Halyomorpha halys, and Dolycoris baccarum which fed on Jangannodu did not emerge, Plautia stali, Piezodorus hybneri, and Nezara antennata which fed on Jangannodu did not oviposit.

톱다리개미허리노린재의 집합페로몬이 노린재검정알벌의 발생에 미치는 영향

The kairomonal activity of the aggregation pheromones of Riptortus clavatus for the egg parasitoid, Gryon japonicum, were investigated in soybean field. The parasitism rate of G. japonicum gradually decreased when the distances between pheromone traps and egg sites were increased from 0 to 15 m. The active distance of pheromone source for parasitoid attraction was estimated to be ca. 15 m. Under field conditions, the parasitoid wasp population peaked during the late August and early September, and the parasitism rate increased when the number of pheromone traps was increased from one to three per . However, insecticide-treated plots, the level of parasitism recorded is relatively low. Sex ratios in field populations of G. japonicum were female-biased.

톱다리개미허리노린재 집합페로몬의 분비변이에 관한 연구

톱다리개미허리노린재(Riptortus clavatus Thunberg) (Heteroptera: Alydidae)의 집합페로몬은 (E)-2-hexenyl (Z)-3-hexenoate (E2HZ3H), (E)-2-hexenyl (E)-2-hexenoate (E2HE2H) 및 tetradecyl isobutyrate (TI)의 세 성분으로 구성되어 있다. 성충의 나이, 교미여부, 채집시기, 체중, 하루 중 시간대에 따른 이들 성분의 분비변이를 조사하였다. 이 집합페로몬의 분비량은 교미여부와 체중 및 하루 중 시간에 따른 차이가 없었다. 그러나 우화 후 일수가 경과할수록 수컷의 집합페로몬 분비량이 많아졌으며, 4월부터 9월까지 채집된 수컷의 집합페로몬 검출량은 10월에 채집된 수컷의 검출량보다 높았으며, 11월과 12월에 채집된 수컷에서는 집합페로몬이 검출되지 않았다. 이러한 집합페로몬의 분비변이 양상을 톱다리개미허리노린재의 먹이이용 전략 및 휴면현상과 관련지어 고찰하였다. Male adults of bean bug, Riptortus clavatus Thunberg (Heteroptera: Alydidae), release aggregation pheromone (AP) which consists of (E)-2-hexenyl (Z)-3-hexenoate (E2HZ3H), (E)-2-hexenyl (E)-2-hexenoate (E2HE2H), and tetradecyl isobutyrate (TI). Variation in the pheromonal secretion were checked by the factors of age, mating status, seasons, body weight and time in a day. There were no significant differences in the amounts of AP secretion by mating, body weight, and time in a day. Higher amount of AP was detected from older males than younger ones. The amount of AP detected was higher in the males collected from April to September than in those collected during October. No AP was detected in the males of November and December. These phenomena in the AP secretion were discussed in relation to food exploitation and reproductive diapause of the bean bug.

Enhancement of Riptortus clavatus (Thunberg) (Hemiptera: Alydidae) egg parasitism by a component of the bug's aggregation pheromone

Egg parasitism of the bean bug, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae), was surveyed using individual egg bags in a sweet persimmon orchard and at Gyeongsang National University (GNU) campus, Korea in 2006. The effect of ( E)-2-hexenyl ( Z)-3-hexenoate (E2HZ3H), one component of R. clavatus aggregation pheromone, on the parasitism enhancement was tested at GNU campus and in a soybean field in 2005 and 2006, respectively. In 2006, two egg parasitoid species, Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae), emerged from R. clavatus eggs. Parasitism by O. nezarae was 9.4–48.3% in mid August to mid September in GNU campus and 6.7–30.0% at the orchard. Total parasitism by G. japonicum (2.5%) at both sites throughout the experimental period was lower than that by O. nezarae (12.5%). This survey revealed nearly no activity of the two species after October at both sites. G. japonicum was solitary and O. nezarae could be either solitary or gregarious. From a single R. clavatus egg, one female or one male G. japonicum emerged. However, an average of 4.3 O. nezarae emerged from one host egg. It took 12.6 d for G. japonicum and 12.0 d for O. nezarae to emerge from R. clavatus eggs in the laboratory. Treatment with E2HZ3H increased parasitism by O. nezarae in both years, but did not increase parasitism by G. japonicum. This suggests that E2HZ3H can be used as a kairomone to reduce the density of R. clavatus in the fields where natural parasitism by O. nezarae is high.

Flight behavior of the bean bug, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae), relative to adult age, sex and season

Studies related to the flight behavior of the bean bug, Riptortus clavatus, an insect pest of soybean, provide information, which can aid the development of management tactics. R. clavatus flight activities were determined using the tethered flight technique in the laboratory and a field study. We compared the flight parameters (flight distance, duration, speed and frequency) of laboratory-reared mated or unmated females and males of different adult age groups, and field-collected females and males from different seasons in a year. Mating effect was only significant for flight frequency, which was higher for unmated adults. Only the flight frequency was different between females and males. Among age groups, 25 d old individuals were shown to have higher flight parameters while the 35 or 45 d old groups showed the lower flight. Among the season, flight activities decreased as the season progressed. The flight distance of R. clavatus in a day was estimated to be 1.6–5.1 km with an average speed of 0.8 m/s from the laboratory data. However, from the field study, it was shown that bean bugs flew a 45–54 m distance with a flight speed of 3.0–3.6 m/s for the first single flight. The second flight was much shorter and slower. We discuss the possible difference of flight parameters between the laboratory and field studies with features of flight mill, variable field conditions and host plant finding behaviors. Further study on flight behavior may provide a better understanding of R. clavatus biology which may guide proper management.

Refrigeration of Riptortus clavatus (Hemiptera: Alydidae) eggs for the parasitization by Gryon japonicum (Hymenoptera: Scelionidae)

Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae) is a solitary egg parasitoid of Riptortus clavatus (Thunberg) (Hemiptera: Alydidae) one of the most important pests in soybean in Korean and Japan. Refrigeration of R. clavatus eggs for up to 120 days was evaluated as a method of mass production of G. japonicum. The refrigeration reduced the eclosion of eggs, thus no nymph emerged after 30 days of egg refrigeration. Increased duration of host acceptance behaviors by G. japonicum and some detrimental effects on parasitism rate, developmental time, longevity, and adult size of the parasitoid were found in refrigerated host eggs. However, all the biological parameters of G. japonicum were unaffected by the refrigeration of up to 30 days. Gryon japonicum parasitized 16 and 14 host eggs daily that were refrigerated for 15 and 30 days, respectively, which did not differ from parasitization of fresh host eggs. Furthermore, refrigeration of host eggs did not reduce the reproduction of the emerged adult parasitoids and emergence and sex ratio of their progeny. Gryon japonicum also parasitized 14 and 13 refrigerated host eggs per day kept at 26.3°C and 78.7% RH for 2 and 4 days of post-refrigeration without significant reduction, respectively. These results show that refrigeration of R. clavatus eggs can be a good method for mass rearing of the parasitoid, and the host eggs killed by cold storage can be supplemented in the field to boost field parasitism.

Inoculation of refrigerated non-viable eggs of Riptortus clavatus (Heteroptera: Alydidae) to enhance parasitism by egg parasitoids in soybean field

Riptortus clavatus Thunberg (Heteroptera: Alydidae) is an important soybean pest in Korea and Japan. Chemical application is a common control method against R. clavatus although it is not always effective at reducing crop damage. As a biological control, the release of refrigerated stink bug eggs has been suggested because the eggs become non-viable but can still be parasitized by parasitoids. We evaluated the inoculation of refrigerated eggs of R. clavatus as a method to enhance natural parasitism. Overall, 9,000–10,600 refrigerated eggs of R. clavatus were inoculated in soybean fields. A higher seasonal parasitism rate on both natural and released host eggs was found at the treated sites. Gregarious parasitoids, including Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and solitary Gryon japonicum Ashmead (Hymenoptera: Scelionidae), emerged from natural eggs. On the released eggs, the parasitism rate by gregarious parasitoids was greatly reduced for an unknown reason. The proportion of bean pods with stylet sheaths as an index of crop damage was also significantly reduced; however, neither the seasonal number of unparasitized eggs nor nymphs and adults of R. clavatus was affected by host egg inoculation. This is the first trial to inoculate non-viable host eggs to enhance natural parasitism.

Temperature-dependent development and oviposition models of Riptortus clavatus (Thunberg) (Hemiptera: Alydidae)

The temperature-dependent development, survival, longevity, and reproduction of Riptortus clavatus (Thunberg) (Hemiptera: Alydidae) were studied at constant temperatures in the laboratory. The mean developmental time from egg to adult emergence ranged from 18.8 d at 36.7°C to 67.0 d at 19.7°C and the lower temperature threshold for the total immature stage (egg to adult emergence) was 15.0°C. The nonlinear shape of temperature-dependent development was well described by the Lactin model. The standardized cumulative frequency distributions of developmental times for each life stage were fitted to the two-parameter Weibull function. Mean adult longevity ranged from 7.83 d at 34°C to 165.14 d at 17.5°C. Mean total fecundity ranged from 29.2 eggs at 34°C to 456.4 eggs at 25°C and was fitted to the extreme value function. Adult survival and the cumulative oviposition rate of R. clavatus were fitted to the sigmoid and two-parameter Weibull function, respectively. We anticipate that the fitted models and parameters will be useful in developing a population model for R. clavatus.