低温贮存和侵染介质微粒大小对S.carpocapsae A_(24)侵染力的影响

本文报道了以不同大小沙粒（Φ120～210μm，210～420μm，420～600μm，600～850μm）作侵染介质，贮存在5℃下349天的S.carpocapsaeA24侵染期线虫和新培养的S.carpocapsaeA24浸染期线虫对大错螟（Galleriamellonella）幼虫的侵染力比较结果。实验表明：以120～210μm或210～420μm沙粒作侵染介质，新培养的A24侵染力都分别显著高于贮存349天的线虫的侵染力，对于420～600μm或600～850μm沙粒作浸染介质，两者均没有显著差异。而无论新培养的A24或低温贮存349天的A24，以Φ120～210μm沙粒作侵染介质下线虫的浸染力与以Φ210～420μm沙粒作浸染介质的线虫侵染力没有显著差异，但都分别高于用Φ420～600μm和Φ600～850μm沙粒作侵染介质的线虫侵染力。

昆虫病原线虫Steinernema carpocapsae All对三种害虫的致病力测定

在实验室条件下测定了昆虫病原线虫小卷蛾斯氏线虫Steinernema carpocapsaeAll对新疆三种重要害虫白星花金龟Postosia brevitarsis Leiwis的2龄幼虫、马铃薯甲虫Leptinotarsa decemlineata(Say)的成虫和梨小食心虫Gra-pholitha molesta Bussck的老熟幼虫的致病力。结果表明:在25℃、RH50%、无光照条件下,用2500IJs/ml(In-fectiveJuveniles/ml)的线虫悬液处理白星花金龟2龄幼虫72h后校正死亡率达100%;用1000IJs/ml线虫悬液处理马铃薯甲虫成虫120h后校正死亡率达100%;用75IJs/ml线虫悬液处理梨小食心虫老熟幼虫48h后校正死亡率达83.33%。在新疆应用昆虫病原线虫小卷蛾斯氏线虫Steinernema carpocapsae All防治上述三种害虫具有很高的潜力。

Potential of Steinernema carpocapsae(Weiser) as a biological control agent against potato tuber moth, Phthorimaea operculella(Zeller)(Lepidoptera: Gelechiidae)

The entomopathogenic nematode,Steinernema carpocapsae,was evaluated for control of the potato tuber moth,Phthorimaea operculella,under laboratory conditions.We evaluated different concentrations of S.carpocapsae for control of 2 nd,3 rd,and 4 th instar P.operculella.The median lethal concentration(LC50)of S.carpocapsae infective juveniles(IJs)to 2 nd,3 rd and 4 th instar larvae of P.operculella was 200,363,181 IJs mL–1,respectively.With the extension of treatment time,the cumulative mortality increased for 2 nd,3 rd,and 4 th instar larvae and pupae of P.operculella.Fourth instars were the most susceptible for all observation periods.Therefore,our results suggest that S.carpocapsae could be an effective biological control agent for P.operculella.

Microbial control of diamondback moth, Plutella xylostella L. （Lepidoptera： Yponomeutidae） using bacteria （Xenorhabdus nematophila） and its metabolites from the entomopathogenic nematode Steinernema carpocapsae

Cells and cell-free solutions of the culture filtrate of the bacterial symbiont, Xenorhabdus nematophila taken from the entomopathogenic nematode Steinernema carpocapsae in aqueous broth suspensions were lethal to larvae of the diamondback moth Plutella xylostella. Their application on leaves of Chinese cabbage indicated that the cells can penetrate into the insects in the absence of the nematode vector. Cell-free solutions containing metabolites were also proved as effective as bacterial cells suspension. The application of aqueous suspensions of cells of X.nematophila or solutions containing its toxic metabolites to the leaves represents a possible new strategy for controlling insect pests on foliage.

A comparative analysis of entomoparasitic nematodes <i>Heterorhabditis bacteriophora</i>and <i>Steinernema carpocapsae</i>

Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with parasitic adaptations that enable them to “feast” upon insect hosts. The infective juvenile, a non-feeding, developmentally arrested nematode stage, is destined to seek out insect hosts and initiates parasitism. After an insect host is located, EPNs enter the insect body through natural openings or by cuticle penetration. Upon access to the insect hemolymph, bacterial symbionts (Photorhabdus luminescens for H. bacteriophora and Xenorhabdus nematophila for S. carpocapsae) are regurgitated from the nematode gut and rapidly proliferate. During population growth, bacterial symbionts secrete numerous toxins and degradative enzymes that exterminate and bioconvert the host insect. During development and reproduction, EPNs obtain their nutrition by feeding upon both the bioconverted host and proliferated symbiont. Throughout the EPN life cycle, similar characteristics are seen. In general, EPNs are analogous to each other by the fact that their life cycle consists of five stages of development. Furthermore, reproduction is much more complex and varies between genera and species. In other words, infective juveniles of S. carpocapsae are destined to become males and females, whereas H. bacteriophora develop into hermaphrodites that produce subsequent generations of males and females. Other differences include insect host range, population growth rates, specificity of bacterial phase variants, etc. This review attempts to compare EPNs, their bacterial counterparts and symbiotic relationships for further enhancement of mass producing EPNs in liquid media.

Storage of osmotically treated entomopathogenic nematode Steinernema carpocapsae

The infective juveniles （IJs） ofSteinernema carpocapsae ‘All＇ were osmotically stressed by a mixture of ionic （fortified artificial seawater） and non-ionic （3.2 mol/L glycerol） solutions to establish a method for osmotic storage of entomopathogenic nematodes. Seven combinations （termed solution A to G） with different proportions of these two solutions were tested, with sterile extra pure water （sepH20, termed solution H） as a control. The mortality of the IJs at a concentration of 5×10^5 IJ/mL in the solutions A to G, and H were 13.2%, 16.2%, 16.7%, 13.5%, 25.2%, 31.6%, 44.6%, and 1.0%, respectively, after 21 days storage at 25℃. Most of the IJs shrunk and stopped motility after 6-9 hours incubation at 25℃ in solutions A to D. Based on the results, solutions A to D and H were chosen to further test the osmotic survival of the IJs at different IJ concentrations （5× 10^5, 2.5×10^5, 2 000 IJ/mL） and incubation temperature （30℃, 25℃, 10℃）. The resulting IJs were exposed to a high temperature assay （45℃ for 4 h, HTA）. Osmotically stressed IJs showed improved heat tolerance. The mortality of the Lls increased with the increasing concentrations of the test Lls and the storage temperatures after exposing to the HTA. More than 88.4%, 62.3% or 2.4% of the treated IJs died at the above three IJ concentrations, respectively. At the three IJ concentrations （2 000 IJs/mL, 2.5×10^5 IJs/mL or 5 ×10^5 IJs/mL）, the highest mortality was recorded in solution D （11.6%, 85.9% or 98.0%, respectively）, and the lowest mortality in solution B （2. 4%, 62.3% or 86.6%, respectively）. No untreated IJs survived after the heat treatment. During 42 days storage at 10℃, the IJs mortality in the solutiors A to D and H were 7.19%, 5.97%, 4.41%, 4.34%, and 4.34% respectively, and showed no significant differences. In conclusion, osmotic treatment of the IJs of S. carpocapsae ‘ All＇ in a mixture of ionic and non-ionic solutions enhances the heat tolerance. The mortality of the IJs after HTA increased with the increasing concentrations of the test IJs and the storage temperatures after exposure to the HTA. The result is promising for the osmotic storage of the entomopathogenic nematodes.

Modulation of immune responses of Rhynchophorus ferrugineus （Insecta： Coleoptera）induced by the entomopathogenic nematode Steinernema carpocapsae （Nematoda： Rhabditida）

Aim of this study was to investigate relationships between the red palm weevil （RPW） Rhynchophorusferrugineus （Olivier） and the entomopathogenic nematode Stein- ernema carpocapsae （EPN）; particularly, the work was focused on the immune response of the insect host in naive larvae and after infection with the EPN. Two main immunological processes have been addressed： the activity and modulation of host prophenoloxidase- phenoloxidase （proPO） system, involved in melanization of not-self and hemocytes recog- nition processes responsible for not-self encapsulation. Moreover, immune depressive and immune evasive strategies of the parasite have been investigated. Our results suggest that RPW possess an efficient immune system, however in the early phase of infection, S. carpocapsae induces a strong inhibition of the host proPO system. In addition, host cell- mediated mechanisms of encapsulation, are completely avoided by the parasite, the elusive strategies orS. carpocapsae seem to be related to the structure of its body-surface, since induced alterations of the parasite cuticle resulted in the loss of its mimetic properties. S. carpocapsae before the release of its symbiotic bacteria, depress and elude RPW immune defenses, with the aim to arrange a favorable environment for its bacteria responsible of the septicemic death of the insect target.

小卷蛾斯氏线虫β-微管蛋白基因的克隆与序列分析

用TRIZOL法提取了小卷蛾斯氏线虫RNA，利用RT-PCR和cDNA末端快速扩增技术（RACE）技术克隆了两条小卷蛾斯氏线虫β-微管蛋白基因cDNA的3＇端序列。将得到的cDNA序列提交到GenBank，分别获取登录号EU049857和EU049858。两个序列，长度分别为1372碱基（SCTUBl）和1374碱基（SCTUB2），分别编码434和432个氨基酸，编码的蛋白的分子量在48kDa左右。氨基酸的124-131位存在一个微管蛋白信号片段GGGTGSG。序列分析表明，分离得到的两个基因与其他线虫的微管蛋白基因具有较高的同源性，核苷酸序列同源性在65％以上，氨基酸序列同源性在81％以上，两个氨基酸序列都含有两个氨基酸保守区NNWAKGHY和RKAFLHWYTGEGMDEMEFTE。

Management of cotton bollworms Helicoverpa armigera and Earias vittella by ento mopathogenic nematodes

Background: The bollworm complex consisting of Helicoverpa armigera and Earias vittella is a major threat in cotton production globally. The habit of developing resistance to many insecticides including Bt transgenic cotton necessitates the exploration of an alternate strategy to manage bollworms. The entomopathogenic nematodes(EPN) Steinernema carpocapsae strain APKS2 and Heterorhabditis bacteriophora strains KKMH1 and TRYH1 at different concentrations of 1 × 10^(9) infective juveniles(IJs)·hm^(-2), 2 × 10^(9)IJs.hm^(-2), and 3×10^(9)IJs·hm^(-2) in 500 L of water were evaluated as a foliar spray in fields naturally infested with H.armigera and F.vittella located at Eastern Block and and Cotton Research Farm of Tamil Nadu Agricultural University, Coimbaotre, India during October 2010–February 2011 and October 2011–February 2012, respectively.Results: In general, all three tested EPN strains reduced the larval population of H. armigera and E. vittella;reduced square and boll damage;and subsequently increased cotton yield compared with the untreated control. The S. carpocapsae APKS2 is most e ective against H. armigera whereas both S. carpocapsae APKS2 and H. bacteriophora KKMH1 were equally effective against E. vittella. The higher dose of 3×10^(9)IJs·hm^(-2) was highly significant in the reduction of H. armigera larvae. However, the doses 2×10^(9)IJs·hm^(-2)and 3×10^(9)IJs·hm^(-2) were equally effective for E. vittella control. The S. carpocapsae APKS2 at 3×10^(9)IJs·hm^(-2) caused a 62.2% reduction of H. armigera larvae, 34% reduction of square damage, 58.5% reduction of boll damage, and yielded 45.5% more seed cotton than the untreated control plots. In E. vittella infested field, S. carpocapsae strain APKS2 and H. bacteriophora strain KKMH1 at 2×10^(9)IJs·hm^(-2)resulted in 60.6%~62.4% larva reduction, 68.4%~70.7% square damage reduction, 66.6%~69.9% boll damage reduction and 45.9% yield increase over the untreated control. The effective EPN treatments were comparable to the chemical insecticide chlorpyriphos 20% emulsifiable concentrate spraying at 2 mL·L^(-1).Conclusions: This study has shown that EPN have great potential in the management of the bollworm complex in cotton. Foliar spraying EPN strain S. carpocapsae(APKS2) at 3×10^(9)IJs·hm^(-2) and S. carpocapsae(APKS2) or H. bacteriophora(KKMH1) at 2×10^(9)IJs·hm^(-2) five times at 10days intervals are the best for the management of H. armigera and E. vittella, respectively.

Assessing immunocompetence in red palm weevil adult and immature stages in response to bacterial challenge and entomopathogenic nematode infection

Parasites and pathogens can follow different patterns of infection depending on the host developmental stage or sex.In fact,immune function is energetically costly for hosts and trade-offs exist between immune defenses and life history traits as growth,de-velopment and reproduction and organisms should thus optimize immune defense through their life cycle according to their developmental stage.ldentifying the most susceptible target and the most virulent pathogen is particularly important in the case of insect pests,in order to develop effective control strategies targeting the most vulnerable individuals with the most effective control agent.Here,we carried out laboratory tests to identify the most susceptible target of infection by infecting different stages of the red palm weevil Rhynchophorus ferrugineus(larvae,pupae,male,and female adults)with both a generic pathogen,antibiotic-resistant Gram-negative bacteria Escherichia coli XL1-Blue,and two specific strains of entomopathogenic nematodes(EPNs),Steinernema carpocapsae ItS-CAO1 and Heterorhabditis bacteriophora ItH-LUI.By evaluating bacterial clearance,host mortality and parasite progeny release,we demonstrate that larvae are more resistant than adults to bacterial challenge and they release less EPNs progeny after infection despite a higher mortality compared to adults.Considering the two EPN strains,S.carpocapsae was more virulent than II.bacteriophora both in terms of host mortality and more abundant progeny released by hosts after death.The outcomes attained with unspecific and specific pathogens provide useful information for a more efficient and sustainable management of this invasive pest.