Insect growth regulators (IGRs) are insecticides that disrupt the normal development of target insects by inducing symptoms such as premature molting or supernumerary larval stages. IGRs are categorized into three types based on their mode of action. One of the them is classified as juvenile hormone agonists (JHAs). In recent studies, we identified juvenile hormone antagonists (JHANs) from plant extracts. In order to identify a novel juvenile hormone agonists and antagonists, we tested 2,354 chemical compounds using the yeast-two hybrid system. Among them, 2 JHAs and 4 JHANs were selected and their insecticidal activities were evaluated against Aedes albopictus larvae. These results may be useful for development of novel IGR insecticides.
Potato Virus Y (PVY) (Potyviridae: potyvirus) is one of the serious emerging virus of seed potato world-wide. It affects the seed potato by transmitting non-persistently via aphids. Here, we developed a simple PVY detection method which used the boiling technique for releasing of the viral RNA from aphid such as stylet and amplification by PVY specific primers located in the viral coat protein gene which suitable for various strains. This simplified method could save the time compared to earlier detection method due to the simplified RNA extraction step. Following this procedure, we tested this one step RT-PCR based PVY detection method by using three PVY vectoring aphid species (M. persicae, A. gossypii and M. euphorbiae) as well as other sucking type insect such as thrips (F. occidentalis). This PVY detection method is rapid, easy-to-use and suitable for large-scale testing in laboratories of seed potato.
Entomopathogenic fungi have been widely studied for their potential as the effective biological control agents. They produce variety of secondary metabolites with insecticidal activities, and it is reasonable to assume that entomopathogenic fungi might produce secondary metabolites modulating juvenile hormone for their survival against defense mechanisms of host insect. In this study, Beauveria spp. and Lecanicillium spp. strains cultured on unpolished rice medium were extracted with acetone. Both extracts showed juvenile hormone antagonist (JHAN) activities in the yeast-two hybrid β-galactosidase assay. In addition, they showed high insecticidal activities against Aedes albopictus, Plutella xylostella, and Ostrinia furnacalis. These results suggested that secondary metabolites of entomopathogenic fungi could be useful for development of novel IGR insecticides.
Streptomyces is the largest genus of Actinobacteria that forms fungus-like branched networks of hyphae. Streptomyces has been clinically important because they produce various secondary metabolites with antibacterial, antifungal, and nematocidal activities. In order to explore novel insecticidal compounds, extracts from 363 strains of Actinobacteria were screened for their juvenoid and anti-juvenoid activities using yeast-two hybrid system. Among them, extract of Streptomyces spp. showed high anti-juvenoid activity. This extract also showed high level of insecticidal activities against larvae of Aedes albopictus, Laodelphax striatellus, and Ostrinia furnacalis. These results suggested that the secondary metabolites of Streptomyces could be natural sources of novel insecticidal compounds.
Insect growth regulators (IGRs) are attractive pest control agents due to their high target specificity and relative safety to the environment. Recently, plants have been shown to synthesize IGRs that affect the insect juvenile hormone (JH) as a part of their defense mechanisms. We identified several JH agonists (JHAs) and antagonists (JHANs) from plant essential oil compounds using a yeast two-hybrid system transformed with the Aedes aegypti JH receptor as a reporter system. They showed high mosquitocidal activities with relatively low LC50 values and caused retardation of ovarian development in female mosquitoes. While the JHAs increased the expression of JH-induced gene, the JHANs caused reduction in the expression of the same gene. The compounds identified in this study could provide insights on the plant-insect interactions and may be useful for the development of novel IGR insecticides.
Bacillus thuringiensis (Bt) produces a variety of insecticidal crystal proteins and widely used as one of the most successful biological control agents. Recently, studies that introduce cry genes into crops to create pest resistance have made much progress, and the total area of land planted with Bt crops has increased substantially. In this study, pest resistance of 8 transgenic Bt rice events with a synthetic cry1Ac gene linked to rice rbcS-tp sequence were assessed under laboratory conditions. Bioassays were performed against Cnaphalocrocis medinalis, which is a significant pest of rice in Asia. C. medinalis larvae were shown to be susceptible to all eight events, even though there were differences between the causes of death. The results differed between developmental stages of the larvae, despite the fact that all 8 events led to high mortalities. These results may be a significant foundation for the evaluation of improved transgenic Bt rice.
Varroa destructor is a devastating ectoparasitic mite which attacks Honeybee, Apis mellifera. V. destructor feeds on honeybee hemolymph, and often harbors small RNA viruses such as the deformed wing virus to transmit these viruses in the infested bee hive. To survey the genes of V. destructor, total RNA was subjected to high-throughput transcriptome sequencing to construct in silico cDNA library by using the Illumina HiSeq 2000 platform. Total of 2×107,748,792 paired-end short reads were obtained and quality filtered reads were subjected to Trinity de novo assembler followed by TransDecoder, and CD-HIT program to make a V. destructor reference cDNA library containing 28,023 of clustered contigs with protein coding capacity. These cDNA sequences will help us to understand the molecular biology of V. destructor.
The small brown planthopper (SBPH), Laodelphax striatellus, is one of the most serious pest insects of rice plants because it can transmit the rice stripe virus (RSV) which often causes significant reduction of yield in the field. Buprofezine is an effective insect growth regular (IGR) pesticide to control planthoppers, however, since the use of buprofezine for more than a decade, it has caused a certain resistance of SBPH. To survey the responses of SBPH to buprofezine, we exposed 4th instar SBPH to 200 ppm buprofezine by dipping method, and extracted total RNA for RNA-seq by Illumina platform. The quality filtered raw reads of cDNA obtained from experimental and control SBPH were subjected to Bowtie2 followed by eXpress computer program to compare the differential gene expression which will be important information for pest control methods using RNAi.
갈색날개매미충은 2010년에 국내에서는 처음으로 충남 공주․예산 등에서 발생이 확인된 후 지속적으로 증가하고 있으며, 기주식물이 매우 다양하다(62과 138종, 2014년). 감, 복숭아, 사과, 매실, 산수유, 블루베리 등의 가지에 약충과 성충이 붙어 즙액을 빨아먹고 분비물을 배출하여 그을음병을 발생시키고, 1년생 가지 속에 난괴를 형성하여 산란함으로서 가지를 고사하게 하는 피해를 주고 있다.
본 연구에서는 블루베리 과원에서의 갈색날개매미충 관리 대책 마련을 위한 기초자료를 얻기 위해 월동알 부화상황, 부화 약충 서식 특성, 전정시기별 부화율, 난괴 발생에 따른 과실특성 등을 조사하였다.
갈색날개매미충은 블루베리를 산란기주로 선호하여 가지에 난괴가 많이 발생하지만 난괴 발생에 따른 과실 품질의 영향은 적었다. 부화 약충은 블루베리를 기주로 선호하지 않아 부화 후에 주변의 다른 기주식물로 이동하여 서식하므로 약충의 흡즙 피해나 그을음 발생도 없었다. 그리고 시기별(12월∼4월)로 난괴가 발생한 가지를 잘라 이듬해 봄에 부화율을 조사한 결과 전 기간에 걸쳐 1.5%를 넘지 않음으로서 난괴가 발생한 전정가지는 특별한 관리를 하지 않아도 되는 것으로 나타났다.
중국에서 매년 우리나라로 비래하는 멸구류의 정밀한 예찰을 위하여 끈끈이트랩을 이용한 들녘단위의 간이예찰법 개발이 필요하다. 본 실험은 끈끈이트랩을 이용한 비래해충의 간이예찰법을 개발하고자 김제 광활, 부안 계화, 고창 해리 3개 지점에 색상은 흰색, 황색, 청색의 끈끈이트랩을 설치하고, 설치방법은 사면, 수평, 수직으로 설치하였다. 유인효과를 살펴본 결과 색상의 경우 황색끈끈이트랩에서 3.2마리로 다른 색상에 비해 유인 포획 효과가 있었고, 설치방법의 경우 수직에서 6.9마리로 많았다. 따라서 끈끈이트랩을 이용한 예찰법은 황색 끈끈이트랩, 수직으로 설치하는 것이 좋은 것으로 생각된다.
벼를 가해하는 벼멸구의 벼 품종별 산란능력을 평가하기 위해 동진1호, 장성벼, 친들벼, 친농벼 등 총 4품종에 접종하여 산란특성을 조사하였다. 동진1호는 벼멸구 저항성 유전인자가 없는 감수성 품종이고, 장성벼는 저항성 유전자인 Bph1, 친들벼와 친농벼는 저항성 유전자 Bph2를 가진 저항성 품종이다. 각 품종별로 10반복 실시하여 총 산란수는 각각 819.1마리, 27.4마리, 290.8마리, 606.0마리로 조사되었다. 그 중 미부화된 알 수를 제외한 부화율은 각각 67.4%, 31.7%, 46.6%, 57.1%로 나타났다. 산란전기간은 각각 8.9일, 3.4일, 5.8일, 8.2일이었고, 난기간은 12.6일, 4.1일, 9.5일, 11.1일로 조사되었다. 암컷 수명은 각각 20.7일, 9.2일, 17.1일, 24.6일로 조사되어 장성벼에서 가장 짧은 수명을 보였다. 4품종에 대한 벼멸구의 산란특성을 비교한 결과, 장성벼에 대한 산란능력이 낮았고, 친농벼에서는 감수성 품종과의 차이가 적은 것으로 조사되었다.
이화명나방의 월동유충 우화율과 성충발생밀도를 비교하기 위해 벼와 억새에서 유충을 채집하고 유인트랩을 설치하였다. 월동유충은 논 1지점(군산), 억새밭 4지점(익산, 화순, 무안, 산청)에서 채집하였는데, 벼에서 126개체, 억새에서 103개체를 확보하여 사육실내에서 인공먹이를 이용, 사육하여 우화여부를 관찰하였다. 그 결과, 벼 개체군은 73%, 억새 개체군은 35%의 우화율을 나타냈다. 이화명나방의 성충발생밀도를 확인하기 위해 논 1지점(군산), 억새밭 1지점(익산)을 선정하고, 이화명나방 페로몬루어를 이용하여 유인트랩을 설치하여 3월 하순부터 10일 간격으로 조사를 실시하였다. 그 결과, 억새밭에서의 성충발생이 논에 비하여 10일 정도 빨랐으며, 4월 하순부터 6월 중순까지 최저 10마리, 최고 27마리로 발생밀도 변화가 크지 않았다. 논에서는 4월 중순에 첫 발생이 확인되어 발생량이 점차 증가하다 5월 하순에 급격하게 증가하여 106마리로 최대 발생하였다. 논과 억새에서의 이화명나방의 발생을 조사한 바, 지역 간에 차이가 있음을 확인하였다.
Amblyseius eharai is a good candidate for biological control agent for major agricultural pest mites such as twospotted spider mites, rust mites, etc. in orchard systems. A. eharai is a native predatory mite of East Asia, and is one of the abundant predatory mites in orchards in Korea. However, ecological studies on this species including its reproductive ability have not been studied yet. Thus, in this study, temperature-dependent developmental rate of adult A. eharai, and three major oviposition related models were studied using six constant temperatures (18.0, 21.6, 24.1, 27.4, 30.2 and 33.2 ℃) with Tetranychus urticae as prey. Temperature-dependent developmental rate, survival rate and oviposition rate of A. eharai adults were well described with a non-linear equation (r2=0.99), a reverse sigmoid function (r2=0.94), and a Weibull function (r2=0.98), respectively. The fecundity was fitted with an Extreme value function (r2=0.99) and the highest in 24.3 ℃. These results would be helpful to verify the abilities of A. eharai as a bio-control agent in the fruit trees.
The occurrence pattern of lepidopteran adults in a paddy-upland rotation field and an organic upland field for 8 maize and 7 sorghum varieties was surveyed from May 8 to September 27, 2016. In addition, their damage ratio and the invasive pores by Ostrinia furnacalis larvae as well as harvest yields were monitored. The density of the lepidopteran adults in two fields showed similar pattern, although a little different pattern in Heliothis assulta. The damage ratio of maize and sorghum varieties by O. furnacalis at harvest periods was depended on both varieties and cultivated environments. A middle negative linear correlation was observed in damage ratios vs yields, the number of invasive pores vs yields, and the number of larvae in corn ears vs yields, but there was not a specific correlation between the damage ratio vs the number of invasive pores. These results may be useful for the establishment of a management strategy to control oriental corn borer in paddy-upland rotation or organic upland fields for maize and sorghum.
Pseudococcus longispinus, a notorious cosmopolitan pest species of mealybugs, known to be distributed indoors in Korea since 2002, is found to be mixed with another species, Pseudococcus orchidicola. Finding P. orchidicola as a pest of tropical plants in Korea is rather unexpected because of their main distribution in Pacific area and South Asia. However, all the available information from morphology, molecule and advices on identification from mealybug specialists indicated this is best matching P. orchidicola. Morphological, molecular and some biological notes on P. orchidicola are provided with some adult and nymphal images, and compared with P. longispinus. A full discussion mainly on identity and distribution of P. orchidicola is given.
The effects of some essential oils and Sopophora extract on Frankliniella occidentalis adults, Myzus persicae adults, Plutella xylostella larvae, and Spodoptera exigua larvae were investigated. Insecticidal and phytotoxicity activities of emulsion in water formulations containing the active essential oils as active ingredients under laboratory and pot conditions were also tested. Based on these results, NRS-13 and NRS-24 formulations were selected to further assess as follows; the GC and GC-MS analysis on the active essential oils, the quantity analysis of the major components contained in the formulations, their insecticidal activities under pot and field conditions, and their oral, dermal, skin and eye irritation, and fish toxicities. Thus, the NRS-13 (BaechooSaferTM) and NRS-24 (JindiOutTM) formulations could be considered as insecticides for pest control.
We developed a simple molecular detection tool that rapidly and accurately identifies Spotted wing Drosophila (SWD) without sophisticated instruments or expertise. We first identified a gene that is present in the SWD genome but not in that of any other insect species. Then, we developed the loop-mediated isothermal amplification (LAMP) assay, which was designed based on genomic DNA of SWD specific gene. This LAMP assay detected only genomic DNA from SWD—not from Drosophila melanogaster. In addition, this assay could detect genomic DNA in SWD geographical strains collected from 8 different locations in Asia, Europe, Hawaii, and the USA. Our LAMP assay could be a useful detection tool for identifying SWD rapidly in the field. This work was carried out with the support of the Cooperative Research Program for Agriculture Science & Technology Development (Project No: PJ0116302016).
The sweet potato whitefly, Bemisia tabaci (Gennadius) and the western flower thrips, Frankliniella occidentalis (Pergande) are major insect pests that causes crop damage worldwide by piercing leaves, sucking sap and transmitting numerous plant viruses. A new strategy for IPM, the push–pull method uses a combination of repellent intercrops (push) and alluring trap plants (pull) to manipulate the distribution of insect pests and control their populations. So, we surveyed the responses of these pests of tomato to several plants in green house. Lavandula angustifolia, Petunia hybrid, Ocimum basilicum and Rosmarinus officinalis showed about forty-percent push response to F. occidentalis in tomato. However, Gypsophila paniculata attracted the F. occidentalis in tomato on the contrary. Pelargonium tomentosum showed about fifty-percent push response to B. tabaci in tomato. However, Mentha spicata and Gypsophila paniculata attracted the B. tabaci in tomato. The utilization technique of these plants should be more inspected in further study.
최근 대추재배 면적이 증가함에 따라 친환경재배농가도 증가하고 있는 추세이다. 하지만 친환경 대추재배 과원은 해충에 의한 피해가 많지만, 시판 유기농업자재 처리 외에는 마땅한 방법이 없다. 따라서 친환경적 방법으로 높은 방제 효율을 보일 수 있을 것이라 판단되는 방충망을 처리하여 해충이 침입하지 못하도록 하였다. 방충망 규격은 직경 0.3mm, 0.75mm, 1mm로 각각 1주씩 설치하고 3반복으로 시험을 수행하였으며 또한 토양의 월동해충이 침입하지 못하도록 바닥에는 차광망을 깔아주었다. 그 결과 대추나무잎혹파리(가칭)의 경우 무처리의 피해잎율이 32.9% 인 반면 방충망 직경 0.3mm, 0.75mm, 1mm의 피해잎율은 각각 0.1%, 2.4%, 13%로 나타났으며, 애무늬고리장님노린재의 경우 무처리의 피해눈율이 21.6%인 반면 방충망 직경 0.3mm, 0.75mm, 1mm의 피해눈율은 각각 7.7%, 4.8%, 5.3%로 나타났다. 이와 같은 결과를 토대로 볼 때 방충망을 사용 할 경우 친환경 대추재배과원에서 해충 방제에 효과적으로 사용 할 수 있을 것이라 판단되며, 또한 방충망 내 수체생육 및 과실 특성 등을 조사하여 방충망 처리에 따른 대추 생육 문제 여부도 조사할 예정이다.
Chlorantraniliprole은 diamide계통의 나비목 유충 방제제로서 기존 살충제들과는 다르게 Ryanodine Receptor (RyR)에 작용하여 Ca2+ 분비에 이상을 유도하여 치사시킨다. 하지만 반복 사용으로 일부 나비목 해충에서 RyR 유전자의 돌연변이에 의한 저항성 계통이 보고되었다. 본 연구에서는 Chlorantraniliprole 저항성 발달 기작을 초파리를 모델 곤충으로 선정하여 수행하였다. EMS 처리로 비특이적 돌연변이를 유도시킨 후, Chlorantraniliprole을 낮은 농도 (5ppm)와 높은 농도 (30ppm)에서 도태를 시작하여 2종류의 저/고도태압 저항성 계통을 확보하였다. 섭식독성 수준을 비교한 결과, 고도태압군의 저항성 수준이 대조군에 비해 약 8배 정도 높게 나타났다. 또한 RyR의 발현량과 생화학적 해독 기전의 차이를 구명한 결과, 2개의 저항성 군집은 대조군보다 전반적으로 높은 생화학적인 해독 기전의 활성화를 보여주었다. 향후 연구는 저항성 기전을 밝혀냄으로써 저항성 회피기작을 알아내는데 도움을 줄 것이다. (본 연구는 농촌진흥청 연구과제 (PJ010821032016)의 지원을 받았음)