Grapholita molesta (Busck) (Lepidoptera: Tortricidae) is an important pest of pome and stone fruits, i.e., apple, peach, and plum. We evaluated single or combined application of an entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin. ARP14 (1×108 conidia/mL) and a botanical insecticide of azadirachtin (Azatrol, PBI/Gordon Cooperation) (10 mL/L) against first instar larvae (<5 h old) of G. molesta in glass scintillation vial bioassay. Combined use of B. bassiana ARP-14 and azadirachtin showed higher corrected morality of 100% at 8 h than 71.4% in λ-cyhalothrin used as a positive control.
A combination using phosphine (PH3) and ethyl formate (EF) was performed to compensate for the disadventages (long exposure time and phytotoxicity) of a single substance. P. longisipinus was more susceptible to mixed phosphine and ethyl formate than P. orchidicola in 12 L dessicator. Mortality of mixed treatment was higher than aggregated mortalities that treated individually, so it indicated to have a synergic effect on each other. Ethyl formate was showed higher adsorption rate than phosphine on imported nursery plants and showed differences depending on the plant. P. longispinus and P. orchidicola was showed 100% mortality when phosphine and ethyl formate was treated as 1 g/m3 and 30 g/m3 for 4 hour in 0.5 m3 fumigation chamber and in 10 m3 container. Phytotoxicity was evaluated to mixture of phosphine and ethyl formate at 1 month after treatment.
Whitefly has a broad host range of more than 600 species, and 40 biotypes have been reported worldwide. Among the various ecological types, B and Q are the most problematic. Especially, Biotype Q, which causes serious damage in the green house, mediates more than 40 kinds of viruses, including Tomato yellow leaf cull virus (TYLCV). The development of resistance to whitefly, adverse effects on non-target organisms, and strengthened legal regulations are making chemical control difficult in application. For these reasons, the use of alternative strategies is needed to suppress the Biotype Q whitefly population. Entomopathogenic fungi were investigated and developed to control hard-control insect pest, such as whitefly. These fungi are natural pathogen of their invertebrate host and contribute to the regulation of their host population in the environment. In addition, these agents are typically harmless to humans and non-targeted organisms and do not adversely impact the environment. Therefore, in this study, we screened pathogenic fungi against whitefly using our entomopathogenic fungal library, and virulence tests were conducted with conoidal suspension (1×107conidia/ml) in laboratory conditions. As a result, 10 isolates showed 80-100% mortality at 5 days after treatment. We will analyze the characteristics of these fungal isolates and evaluate their potential as insecticides against whitefly. The selected isolates against the high mortality of whiteflies can be effectively used in integrated pest management programs for whiteflies.
Spotted wing drosophila (SWD), Drosophila suzukii, is a serious pest of berry fruits and grapes in East-Asia and USA. SWD female oviposits eggs into the skin of ripening fruits, and the larvae dig a burrow inside the fruits. Secondary infestation by other insects and pathogens to the oviposition spots cause substantial economic damages worldwide. SWD has recently been spreading to Europe and USA, and it is becoming a global threat in terms of biosecurity. A quite useful paper has been published in Journal of Chemical Ecology in the most recent issue (Vol. 44, #10) which is titled ‘Advances in the chemical ecology of the spotted wing drosophila (Drosophila suzukii) and its applications’ written by Cloona et al. This article introduces chemical constituents from many odor sources such as fermentation, yeast, fruit, and leaf sources, and commercial lures and traps developed using these compounds. Authors said that the current food-based lures and trap technologies are not expected to be specific to SWD and thus capture large numbers of non-target drosophilids. Attractive and aversive compounds are being evaluated for monitoring, mass trapping, and for the development of attract-and-kill and push-pull techniques to manage SWD populations. (Supported by PJ011756022018, RDA)
Azuki bean beetle (ABB), Callosobruchus chinensis (L.) is a cosmopolitan field-to-storage pest of legumes. Its female sex pheromone consists of two isomeric components, 2Z-homofarnesal and 2E-homofarnesal. Two day old virgin adults were exposed to sub-lethal fumigation doses (LC25=2.80 and LC50=3.32 mgL-1) of ethyl formate (EF) to see the effects on adult longevity, fecundity, sterility and female sex pheromone production. Longevity (female; P < 0.001, male; P < 0.001), fecundity (P < 0.001) and sterility (P < 0.001) were significantly affected. The Gas Chromatography-Mass Spectrometry for solid phase micro extraction revealed that release of both of the pheromone components were not affected by LC25 dose of EF. However, the fecundity (per female/day) was significantly (P < 0.001) stimulated by the tested EF doses when the female adults were treated irrespective of the male treatment, probably revealing a hormetic effect. This study provides insight into the effect of EF fumigation on biological activities of C. chinensis.
Pine wood nematode (Bursaphelenchus xylophilus), the pathogen of pine wilt disease (PWD), is transmitted to new host trees through Monochamus spp., vector insects. In Korea, aerial application has been allowed conventionally to eliminate the vectors in their flying season. In this study, thiacloprid was applied to four-year-old Pinus densiflora, which were fed to adult M. alternatus emerged from PWD infected logs for 72 h in the condition of 1 DAT (Days after treatment of thiacloprid) and 15 DAT, respectively. We confirmed the presence of nematodes in each beetle applied to experiment by Baermann funnel method and PCR with species-specific ITS primers. After 72 h of 1 DAT and 15 DAT, thiacloprid residues in pine trees were 0.59-16.32 and 0.043-0.131 mg/kg and the mortalities of the beetle were 100 and 99.2%, respectively. Detection rate of B. xylophilus was 51.3%. The incidence rate of PWD in 1 DAT and 15 DAT showed no mortality and 5.55% compared with 55.5% of control, respectively.
IKK-γ is an essential protein to form IKK complex which regulate NF-κB. We identified TmIKK-γ (or TmKenny) gene which has 1,521 bp of nucleotides encoding 506 amino acid residues. Domain analysis of TmIKK-γ shows that there are one NF-κB essential modulator (NEMO) domain and a leucine zipper domain. Expression of TmIKK-γ gene was gradually increased from egg to 2-day-old pupal stage, dramatically decreased until 7 day-old pupal stage, and then it was gradually increased. TmIKK-γ transcripts were highly expressed in fat body and hemocytes in late instar larvae and integuments, fat body and Malpighian tubules in 5 day-old adult. TmIKK-γ was drastically induced by E. coli after 3 h challenges and by S. aureus at 3 and 12 h-post injection in hemocytes. TmIKK-γ was not induced by C. albicans although it was significantly induced by E. coli (at 3, 6 and 24 h) and S. aureus (at 9 h) in gut. In fat body, expression of TmIKK-γ was drastically induced by E. coli at 3 and 24 h-post injection while it was not significantly induced by S. aureus and C. albicans. To understand the immunological role of TmIKK-γ, gene specific RNAi and mortality assay was performed. larval mortality against microbial challenge was dramatically increased by TmIKK-γ RNAi. Furthermore, we investigate the tissue specific induction patterns of fourteen AMP genes in response TmIKK-γ dsRNA-treatment. In fat body, ten AMP genes out of fourteen was not significantly induced by microbial challenge in TmIKK-γ dsRNA-treated group. Based on these results, TmIKK-γ might play an important role in antimicrobial innate immune responses in Tenebrio molitor.
Laodelphax striatellus is an important pest of rice due to not only sucking rice seedlings, but also transmitting serious plant viruses. Among various kinds of insecticide groups (carbamates, organophosphorus, neonicotinoids, etc.), carbofuran, a systemic carbamate insecticide, has been most extensively used to control rice pests including L. striatellus, resulting in widespread carbamate resistance in Korea and other Northeast Asia countries. To identify the genes associated with carbofuran resistance, we obtained a 14-fold higher resistant strain (SEL9) from the mixed-field population (SEL0) by consecutive selection. A transcriptome-based analysis was conducted and differentially expressed genes (DEG) were compared between the SEL9 and SEL0 strains. A total of 96,185,150 reads were analyzed, of which 62,860,430 reads were mapped. From these reads, 15,356 transcripts were annotated. A total of 327 up-regulated and 275 down-regulated genes were identified in the resistant SEL9 strain compared to SEL0 strain by DEG analysis. Gene ontology (GO) analysis was performed using DEGs showing statistical significance (P < 0.05). The GO analysis identified 1,320 genes in biological process group, 1,100 genes in cellular component group and 428 genes in molecular_function group.
The world’s climate is changing. This can affect agricultural insects and the damage they cause by altering their ecology, behavior and habitats. Aphids are emerging as an indicator of climate change, and they are a good model for understanding these environmental changes, especially based on their migratory behavior. In this study, the occurrence of aphids in a seed potato field in Pyeongchang, Korea, was monitored daily using a yellow water pan trap from 1977 to 2017. During these 40 years, the annual migration fluctuations of the aphids were analyzed, with particular focus on four species known to vector potato viruses, Aphis gossypii, Aulacorthum solani, Macrosiphum euphorbiae, and Myzus persicae. It was found that, as time goes by, the start point of spring migration in these aphid species was getting earlier while the peak in autumn migration gradually moved to the winter season. Together with a mean annual temperature increase of 1.03 °C in Pyeongchang over the past four decades, there is a potential threat of expansion in the distribution of aphid species. that this temperature change could influence the aphid’s population changes in the Korean peninsula.
딱정벌레목 바구미과에 속하는 나무좀은 일찍부터 산림의 주요 해충으로 다루어져 왔다. 최근 사과원에서 M.9 대목을 이용한 사과 밀식재배가 확산되고, 기후변화에 따른 이상 기상으로 사과나무 동해에 의한 2차 나무좀 피해가 늘어나고 있어 이들에 대한 관리대책이 필요한 실정이다. 본 연구는 사과원에 발생하는 나무좀류의 발생 양상을 파악하고 효과적인 약제 선발을 통해 효율적인 방제 체계 개발을 위한 기초 자료로 활용하고자 수행하였다. 사과원에 발생하는 나무좀은 암브로시아나무좀, 오리나무좀, 붉은목나무좀, 사과둥근나무좀 등 4종으로 암브로시아나무좀이 우점종으로 조사되었다. 암브로시아나무좀의 발생은 4월부터 시작하여 연 2회 발생하였다. 주간부에서 나무좀의 피해는 대부분 21~100cm 높이에서 발생하였으며, 야외 방제 시험에서 Phentoate EC, Chlorpyrifos WP, Thiacloprid SC 등이 높은 방제가를 나타내었다.
세계화로 인해 교역 및 여행객의 증가로 외래 병해충의 유입이 증가하고 있고 이들의 유입 및 확산 경로 규명을 위하여 분자 유전학적 분석 방법이 이용되고 있는 실정이다. 본 연구는 외래 해충인 Reticulitermes kanmonensis의 유전적 특성을 분석하기 위한 18개의 초위성체마커(microsatellite)를 이용하여 총 16개 지역(전주, 김제1, 김제2, 군산1, 군산2, 서천, 완주1, 완주2, 완주3, 완주4, 익산1, 익산2, 논산, 일본1, 일본2, 일본3)의 흰개미 244개체를 분석하였다. 집단간 대립 유전자 패턴(allelic patterns)분석결과 일본3 지역의 유전적 다양성이 높게 나타났고 완주2 지역은 다른 지역에 비해 비교적 낮게 나타났다. 집단 간 유전적 거리(Genetic differentiation)는 평균적으로 0.163정도의 유전적 다향성 비율을 나타냈고, 서천과 군산2 지역이 0.048로 낮게, 서천과 일본2 지역이 0.442로 높게 나타나 서천과 군산2 집단이 유전적으로 가깝게 나타나고, 반면 서천과 일본2 집단과는 유전적으로 멀게 나타났다. STRUTURE 분석결과는 클러스터 집단 수가 6(k=6)일때 이상적인 집단 패턴을 나타내었고, 유전적 구조는 A그룹(전주, 김제1, 완주2), B그룹(서천, 군산1, 군산2), C그룹(완주1, 김제2), D그룹(논산, 익산1, 익산2), E그룹(김제1, 완주2, 완주3), F그룹(일본1, 일본2, 일본3)의 6가지의 패턴이 지역별로 분리되어 나타났다.
In this study we present a new approach to estimating termite populations size. So far, termite researchers have been using the mark-capture-recapture method. This method has a disadvantage that measurement time is long and error range is large. To this end, we built an agent-based model to simulate termite tunneling behavior. Using this model, we made simulated tunnel patterns that are determined by three variables: the number of simulated termites (N), the passing probability of two encountering termites (P), and the distance that termites move soil parcels (D). To explore whether the N value can be estimated with a partial termite tunnel pattern, we generated four groups of tunnel patterns that are partially obscured in complete tunnel pattern image: (1) A pattern group in which the outer area of the tunnel pattern is obscured (I-pattern), (2) a pattern group in which half of the tunnel pattern is obscured (H-pattern), (3) a pattern group in which the inner region of the tunnel pattern is obscured (O-pattern), and (4) a pattern group combining I- and O-pattern (IO-pattern). For each group, 80% of the tunnel patterns were learned through a convolution neural network (CNN) and the remaining 20% of the patterns were used for estimating N value. The estimation results showed that the N estimates for the IO-pattern are the most accurate and are in the order I-, H-, and O-patterns. This means that the termite population size can be estimated based on tunnel information near the center of the colony.
Small hive beetles (SHBs) are parasites of bee colonies and is one of the invasive pest species worldwide. In this study, we aimed to investigate a chemical responsible for the attractiveness of a hive to this pest. Based on the laboratory observation, we found the fermented pollen dough (honey bee food) was highly attractive to adult SHBs. Olfactometer bioassay showed the crude methanol extract of this material is attractive to both sexes (> 60%). However, the methanol extracts of fresh honey and pollen patty which we used as a food of SHB were not attractive to the pest. The crude methanol extract of fermented pollen dough was subjected to partitioning with n-hexane, chloroform, ethyl acetate, and n-butanol. The n-hexane and chloroform fractions were attractive > 80% for both sex SHBs. On the other hand, ethyl acetate and n-butanol were repulsive >70% and >80%, respectively. The wandering larvae of the pest showed a reverse response for the solvent fractions observed in adults. HPLC and GC-MS analysis indicated the methanol extract of fermented pollen dough constitute butanoic acid (7.70%), neopentylamine (7.29%), (E)-9-octadecenoic acid ethyl ester (3.89%) and hexadecanoic acid, ethyl ester. While these compounds were not found even in a trace level in the methanol extract of honey and pollen patty. Based on this findings these constituents of the fermented pollen dough were formed by the action of SHB and its larvae and we believe these volatile organic compounds are responsible for attractiveness to SHB as pollen dough undergoes attach by SHB and ferment. We are working on investigating attractiveness of each of these chemicals toward the pest. We recommend further work on these chemicals for their application to control this pest.
We evaluated three previously known repellents of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), i.e., carvacrol, cis-jasmone, and methyl jasmonate for the attraction of commercialized predators, Orius laevigatus (Fieber) (Hemiptera: Anthocoridae), and native predator, O. minutus (L.), in Y-tube olfactometer. Higher proportion of O. laevigatus (mated unfed adult females) moved to the arm of methyl jasmonate or cis-jasmone than the arm of clean air. However, O. minutus did not show any significant preference to the chemicals tested. These results suggest that, among the tested chemicals, methyl jasmonate or cis-jasmone would be a good attractant for O. laevigatus.
To find best humidity condition for the use of Beauveria ARP14 against Grapholita molesta (Busck), first instar of G. molesta was treated with three conidial concentrations (1×107, 1×108, and 1×109 conidia/ml) in three different relative humidities (RH; 55, 75, and 95%). Mortality varied depending on concentration and humidity. Mortality in 95% RH was 1.5 and 2.7 times higher than 75 and 52% humidity at 1×109 conidia/ml and 16 hours after the exposure. However, the mycosis rates after 14 days were all not different among the treatments. In conclusion B. bassiana ARP14 could be most effective when applied higher at RH condition.
Residual contact vial (RCV) method was used to monitor insecticide resistance in field populations of the melon thrips, Thrips palmi. Median lethal doses (LD50) at 8 h post-treatment of six insecticides (chlorfenapyr, cyantraniliprole, cypermethrin, dinotefuran, emamectin benzoate and spinosad), which are commonly used for T. palmi control, were determined at 8 h post-treatment using a susceptible RDA strain. The diagnostic doses for on-site resistance monitoring of the six insecticides, which were determined as two-fold higher doses of LD90 for the RDA strain, were in the range of 0.299 to 164,25 μg-1cm2. To test the applicability of RCV for T. palmi, insecticide resistance levels in three field populations (Gyeonggi; GG_AS, Chungbuk; CB_CJ, Jeonbuk; JB_KJ) were evaluated. Field populations showed reduced mortality (0-50% mortality) to spinosad, cypermethrin, cyantraniliprole and emamectin benzoate, that they have different degree of resistances to these insecticides. In particular, all test field populations exhibited 0% mortality to spinosad, suggesting wide spread of spinosad resistance in the field. Moreover, no detectable mortality to emamectin benzoate was observed in JB_KJ strain, suggesting uneven distribution of emamectin benzoate resistant population of T. palmi. To provide more precise information on resistance profiles and distribution in T. palmi populations, it would be necessary to conduct a large scale resistance mapping for broad geographical regions.
Entomopathogenic fungi have been known as promising candidates for biological control of insect pests. Recently, researchers consider the fungal thermotolerance in formulations and field applications. In this study, we investigated the production of thermotolerant Isaria javanica and I.fumosorosea conidia through grain-based solid cultures and exposure to light stress. As results, of the ten grain substrates, Italian millet, rice, perilla seed and sesame, rice, sorghum produced highly thermotolerant conidia in the strains. The two strains were exposed to a light stress and showed enhanced thermal stability compared to control, when exposed to 45°C for 2 hours. This work suggests that heatresistant entomopathogenic fungal conidia can be produced by grainbased solid cultures and exposure to light stress.
Thrips is one of the serious insect pests in many economic crops, in which general managements rely mainly on chemical insecticides. However, the overuse of chemicals led to the development of insect resistance and environmental residual issues. Therefore, thrips management requires the consideration of alternative strategies which are less harmful to the environment and working on different target points. In this work, we isolated entomopathogenic fungi from soil, and identified them with morphological and molecular biology methods, followed by a preliminary virulence assay against Tenebrio molitor larvae. Selected fungal isolates were adjusted to 1×107 conidia/ml for an indoor virulence assay against thrips adults, and highly virulent isolates were added to a thrip-pathogenic fungal library. Biological characteristics of efficacious isolates were investigated comparing to a previously commercialized fungal isolate. This entomopathogenic fungal library could be used as a valuable resource for developing effective strains to control thrips in agricultural fields.
RNA interference (RNAi)-based strategy has been developed to control various phytophagous chewing pests. However, only a few cases of RNAi-based control success have been reported for sucking pests, suggesting that sucking pests likely ingest less amount of transgenic subcellular hairpin RNA (or dsRNA). In this study, as the basic information for the establishment of ingestion RNAi against sucking pests, feeding amount and time course of plant subcellular fractions of the four sucking pest species (Frankliniella occidentalis, Frankliniella intonsa, Tetranychus urticae and Nilaparvata lugans) were determined by quantitative PCR (qPCR). Adults of the four species were starved for 24 h and then fed with kidney bean leaf (F. occidentalis, F. intonsa, T. urticae) or rice leaf (N. lugens) for 48 h. The leaf-fed adults were collected every 6-h interval and their genomic DNA was extracted. The ingested fractions of chloroplast and nuclear were quantified using rubisco and 50s rRNA as marker genes, respectively. The ingested amount of rubisco and 50s rRNA genes in F. occidentalis, F. intonsa and T. urticae showed rapid increasing pattern after feeding and then slightly reduced over time. In contrast, N. lugens neither ingest nuclear nor showed any distinct feeding pattern of chloroplast. These results demonstrate that F. occidentalis, F. intonsa and T. urticae ingest both chloroplasts and nucleus along with cytosol as cell-feeders but N. lugens, a phloem sap feeder, does not ingest nucleus during sucking. Our findings further suggest that ingestion RNAi-based control strategy would work better for cell-feeding sucking pests compared to phloem sap-feeding sucking pests.
Longhorned tick, Haemaphysalis longicornis (Ixodida: Ixodidae) is one of the vectors of severe fever with thrombocytopenia syndrome virus (SFTSV) in human. The tick occurs in mostly grass fields, and the use of pyrethroid insecticides induced pest resistance and environmental residual toxicity. Particularly the use of chemicals near residential areas where persons live become a big issue, so environmentally safe control agents need to be considered. Here in this work, our interest was given to the selection of highly virulent fungi against H. longicornis. A total of 101 fungal pathogens collected from mountainous areas were assayed by a dipping the nymph stage of ticks into a conidial suspension (1×107conidia/ml). Interestingly among several species, one species showed high virulence and mycosis were observed in 7-15 days. Most of the selected isolates produced a large amount of conidia in Italian millet, rice and millet with thermotolerance at 40-45°C. Based on these results, we selected a couple of isolates with high virulence against H. longicornis and they could be used for the control of the ticks after the set-up of a practical application strategy in fields by optimizing fungal colonization in soil and phyllosphere.