菜蛾盘绒茧蜂主要寄生因子对寄主小菜蛾生长发育的调控

研究了菜蛾盘绒茧蜂的主要寄生因子(多DNA病毒、毒液和畸形细胞)对寄主小菜蛾生长和发育的影响.通过利用结合假寄生和过寄生方法,证明寄生蜂寄生因子对寄主生长和发育有明显影响.结果显示,假寄生初期,寄主体重降低;但到后期,当未寄生寄主正常化蛹后,假寄生寄主继续取食、发育,寄主末龄幼虫期显著延长,不能化蛹,成为超重幼虫,最大体重可达10.52mg.正常寄生后,寄主的发育与未寄生寄主相比,始终处于抑制状态.过寄生对寄主生长、发育的抑制程度加剧.研究结果表明,假寄生与正常寄生后寄主的生长和发育有明显差异,这种差异的部分原因可能是由畸形细胞引起的.     

寄主抗药性对菜蛾绒茧蜂寄生能力的影响

考察了在使用氰戊菊酯的条件下 ,小菜蛾抗药性对菜蛾绒茧蜂寄生能力的影响。在杀虫剂作用下 ,用抗性寄主饲养的菜蛾绒茧蜂RRC品系对抗性寄主RRP品系幼虫的寄生率达89% ,寄主幼虫死亡率仅 5% ,比RRC对小菜蛾敏感品系SSP幼虫寄生时、或用SSP饲养的菜蛾绒茧蜂SSC品系对SSP寄生时的寄生率显著要高 ,寄主死亡率显著要低。表明杀虫剂存在时 ,寄主抗药性使其具较高存活率而给寄生蜂提供更多的寄主 ,有利于寄生蜂的繁衍。方差分析结果显示 ,小菜蛾品系及蛾×蜂互作对供试小菜蛾幼虫的被寄生率及死亡率均有显著影响 ,表明小菜蛾抗性改变了其对菜蛾绒茧蜂的适合性     

温度对菜蛾绒茧蜂生长发育、存活和繁殖的影响

在１５－３５℃范围内的９个温度下测定了温度对菜蛾绒茧蜂Ｃｏｔｅｓｉａ ｐｌｕｔｅｌｌａｅ Ｋｕｒｄｊ．的个体发育,种群存活率和种群增长潜能的影响。卵－结茧,结茧羽化两阶段的发育速度与温度均呈直线关系,发育起点温度分别为１０．６和１１．８℃,有效积温常数分别为１０５．６和６２．０日度。     

菜蛾绒茧蜂的寄主选择性及寄生对寄主发育和取食的影响

研究了菜蛾绒茧寄生对寄主幼虫龄期的选择性及对寄主生长发育、取食量的影响。结果表明,该蜂能寄生小菜蛾各个龄期的幼虫,但当２－４龄幼虫同时存在时,偏爱寄生２、３龄幼虫,对２、３、４龄幼虫的选择系数分别为０．３７、０．３９、０．２４。该蜂对４龄幼虫的寄生能力随寄主日龄增大而急剧下降,对进入４龄并发育至该龄期４０％时间以上的幼虫不能寄生。产卵寄生的雌蜂比例也随４龄幼虫日龄增大而急剧下降。小菜蛾幼虫被寄主后     

常用杀虫剂对菜蛾绒茧蜂的影响及毒理机制研究

田间采集试虫室内测定结果表明,敌敌畏、灭多威和杀虫双对菜蛾绒茧蜂Apanteles plutellae高毒,乙酰甲胺磷对绒茧蜂毒性较低,而氰戊菊酯、氯氰菊酯、氟虫腈、阿维菌素、定虫隆和Bt则是低毒的。菜蛾绒茧蜂AChE的Km及Vmax值分别是小菜蛾的0.22和2.08倍,AChE对敌敌畏的敏感性(K/em>i值)分别是小菜蛾的10.37倍。100 mg/L的胡椒基丁醚(PB)或磷酸三苯酯(TPP)均可使氰戊菊酯明显增效,其中PB的增效作用显著高于TPP。体内抑制实验结果表明,PB和TPP对绒茧蜂AChE活力无显著影响,低浓度(100 mg/L)的PB即可显著抑制绒茧蜂的α-NA和β-NA CarE活力,且抑制率高于TPP,TPP仅在高浓度(1 000 mg/L)时对绒茧蜂的两种CarE活力有显著抑制作用。由此推断,与小菜蛾相比,菜蛾绒茧蜂对有机磷的高敏感性与其显著较高的AChE敏感性有关;此外,多功能氧化酶的解毒代谢在菜蛾绒茧蜂对氰戊菊酯的耐药性中具重要作用。     

菜田常用杀虫剂对小菜蛾及菜蛾绒茧蜂的选择毒杀作用

在室内测定了９种菜田常用杀虫剂对小菜蛾幼虫及其主要天敌菜蛾绒茧蜂成虫和茧的毒性。结果表明,应用厂家推荐田间防治小菜蛾的使用浓度,对小菜蛾的杀虫效果锐劲特、Ｂｔ、虫螨光可达１００％,生物复合病毒杀虫剂、宝路和抑太保可达９５％以上,杀虫双达８０％,而氰戊菊酯和万灵对小菜蛾的杀虫效果较差,供试幼虫最终化蛹率分别达７０．０％和７８．３％。让菜蛾绒茧蜂成虫接触厂家推荐浓度的药膜,接触杀虫双２小时后的死亡率即达８０％以上;１２小时后,接触锐劲特的死亡率即达１００％;２４小时后,接触万灵和杀虫双的累计死亡率达９０％以上,接触宝路和氰戊菊酯的约５０％,而接触抑太保、Ｂｔ、虫螨光和生物复合病毒杀虫剂的累计死亡率均在２０％以下,和对照无显著差异。作者认为在菜蛾绒茧蜂等天敌较为丰富的季节,虫螨光、Ｂｔ、生物复合病毒杀虫剂、宝路和抑太保应属防治小菜蛾优先选用的杀虫剂,锐劲特则主要应在小菜蛾大发生、而天敌又很少时应用。     

母代光照经历对菜蛾盘绒茧蜂滞育发生的影响

室内研究了在同一温度(25℃)3、种不同光照条件(8L∶16D、12L∶12D、16L∶8D)下饲养的菜蛾盘绒茧蜂,其后代在4种不同温度(13、15、17、20℃)和2种光周期(8L∶16D、11L∶13D)下饲养的滞育率变化情况。结果表明:母代的光照经历、子代饲养温度和光照周期这3个滞育诱导因素都会显著地影响滞育率。母代的光周期经历与子代诱导滞育的温度或光周期之间、子代诱导滞育的温度与光周期之间均存在交互作用,但3个因素间的交互作用不显著。母代在长日照条件下饲养可以降低子代诱导滞育的临界温度。子代在较低温度下饲养,母代经历的光周期对子代滞育的发生影响不大,甚至没有影响;但当子代在相对较高温度下饲养,母代经历的光周期对子代滞育发生的影响十分明显。     

氰戊菊酯施用于寄主幼虫对菜蛾绒茧蜂的致死和亚致死效应

25℃下,分别在菜蛾绒茧蜂产卵寄生后的第1、3、5、7天(幼蜂分别处于卵、初龄幼虫、中龄幼虫、末龄幼虫期)将20％氰戊菊酯乳油1000倍水溶液以喷雾法施用于被寄生的小菜蛾幼虫。第1天和第7天处理使蜂的存活率明显下降,第1天处理导致育出雌蜂的产卵量低于对照,而第3天和第5天处理使蜂存活率下降幅度相对较小,且第5天的处理引起育出雌蜂的产卵量高于对照。不同时间处理均显著延长了该蜂卵 幼虫的发育历期,其中以第5天延长最为显著。除第3天外,其余时间处理导致育出蜂个体小于对照,且以第1天和第7天处理影响更为显著。羽化雌蜂的寿命均短于对照。对存活率和产卵量进行综合分析表明,氰戊菊酯施用于寄主幼虫对菜蛾绒茧蜂幼蜂的影响随后者发育阶段不同而变化,卵、末龄幼虫期较初龄、中龄幼虫期受到的不利作用更大。     

小菜蛾内寄生蜂--菜蛾盘绒茧蜂的种内竞争

在室内（25±1）℃,以小菜蛾3龄幼虫为初始寄主,对过寄生后,小菜蛾幼虫内寄生蜂--菜蛾盘绒茧蜂的种内竞争进行了研究。当2头雌蜂同时寄生（10 min内）同一头寄主,2 d后几乎同时孵化的茧蜂幼虫总有一头1龄幼虫利用发达的角质化上颚攻击同类竞争者。当两次寄生间隔时间为24、48和72 h时,先寄生的茧蜂幼虫分别以86.7%,95.0%和96.9%的比例在发育中占据优势,1龄幼虫使用上颚将后孵化的初孵幼虫杀死,或直接攻击蜂卵致使包囊、黑化的发生,此时物理攻击发挥主要作用,并可能通过先寄生者释放畸形细胞、水解酶等生理抑制方式完全阻碍后产入的蜂卵的发育。当两次寄生间隔时间长达96或120 h,因寄主已不适合茧蜂的再次产卵寄生,致使过寄生率由100%分别下降为69.4%和60.7%;已发生过寄生的个体中,80.0%以上以先寄生者吐丝、结茧化蛹,后寄生者则伴随被过寄生寄主的死亡而不能完成发育。以上结果表明,当种内竞争发生时,菜蛾盘绒茧蜂可通过物理攻击和生理抑制两种途径排除同类竞争者,竞争结果主要取决于雌蜂2次寄生的先后顺序。     

小菜蛾内寄生蜂——菜蛾盘绒茧蜂的种内竞争

在室内(25±1)℃,以小菜蛾3龄幼虫为初始寄主,对过寄生后,小菜蛾幼虫内寄生蜂——菜蛾盘绒茧蜂的种内竞争进行了研究。当2头雌蜂同时寄生(10 min内)同一头寄主,2 d后几乎同时孵化的茧蜂幼虫总有一头1龄幼虫利用发达的角质化上颚攻击同类竞争者。当两次寄生间隔时间为24、48和72 h时,先寄生的茧蜂幼虫分别以86.7%,95.0%和96.9%的比例在发育中占据优势,1龄幼虫使用上颚将后孵化的初孵幼虫杀死,或直接攻击蜂卵致使包囊、黑化的发生,此时物理攻击发挥主要作用,并可能通过先寄生者释放畸形细胞、水解酶等生理抑制方式完全阻碍后产入的蜂卵的发育。当两次寄生间隔时间长达96或120 h,因寄主已不适合茧蜂的再次产卵寄生,致使过寄生率由100%分别下降为69.4%和60.7%;已发生过寄生的个体中,80.0%以上以先寄生者吐丝、结茧化蛹,后寄生者则伴随被过寄生寄主的死亡而不能完成发育。以上结果表明,当种内竞争发生时,菜蛾盘绒茧蜂可通过物理攻击和生理抑制两种途径排除同类竞争者,竞争结果主要取决于雌蜂2次寄生的先后顺序。     

Effect of antifeedants on the diamondback moth (Plutella xylostella) and its parasitoid Cotesia plutellae

Two neem preparations and the bitter‐tasting synthetic chemical denatonium benzoate were tested in the laboratory as antifeedants against the diamondback moth, Plutella xylostella L. The effects of the three materials on Cotesia plutellae (Kurdjumov), a hymenopteran parasitoid of ­P xylostella, were also recorded. All three materials significantly reduced the food consumption of ­P xylostella larvae. Parasitoid cocoons were formed on approximately half of those larvae which had been exposed to female C plutellae, regardless of antifeedant treatment, but emergence of adult parasitoids from the cocoons was significantly reduced by antifeedant treatment. In terms of food consumption and mortality of unparasitised P xylostella larvae, and emergence of adult C plutellae, the effect of each antifeedant preparation was directly related to the concentration of material used, but the effects of the neem preparations were greater than those of denatonium benzoate. However, no adult P xylostella emerged on any antifeedant treatment, therefore some of the parasitoids survived antifeedant treatments which were fatal to the unparasitised hosts. © 2000 Society of Chemical Industry     

Evaluation of selective toxicity of five pesticides against Plutella xylostella (Lep: Plutellidae) and their side-effects against Cotesia plutellae (Hym: Braconidae) and Oomyzus sokolowskii (Hym: Eulophidae)

The toxicities of five pesticides commonly used in vegetable fields to the larvae of the diamondback moth, Plutella xylostella (L) and its two major parasitoids, Cotesia plutellae (Kurdjumov) and Oomyzus sokolowskii (Kurdjumov), were evaluated in the laboratory using several bioassays. When tested at the rates recommended for field application by the manufacturer, fipronil, avermectin and chlorfluazuron produced over 95% mortality on third-instar larvae of P xylostella, but fenvalerate and methomyl did not produce any substantial mortality to such larvae, and over 70% of P xylostella larvae could still pupate normally after feeding on cabbage leaf treated with the two pesticides. In a residual contact assay with adult parasitoids, fipronil and methomyl caused over 93% mortality within 24 h; fenvalerate killed approximately 55% of the adults within 24 h; avermectin and chlorfluazuron showed differential toxicity to the two parasitoids. Avermectin was extremely harmful to O sokolowskii but slightly toxic to C plutellae, while chlorfluazuron was more toxic to C plutellae than to O sokolowskii. In the residue assay with cocoons of C plutellae and pupae of O sokolowskii developed within P xylostella pupae, treatments with pesticides did not reduce adult emergence. However, the mortality of C plutellae adults emerged from the fipronil-treated cocoons increased greatly within 24 h post-emergence; adults from the fenvalerate-treated cocoons parasitized less host larvae. Treatments with fenvalerate and methomyl significantly increased the mortality of O sokolowskii adults within 24 h post-emergence. Recommendations of choosing pesticides for the control of P xylostella are given.     

小菜蛾和绒茧蜂乙酰胆碱酯酶对甲胺磷和甲基异柳磷敏感性监测

对 ACh E的 K m、Vmax和 Ki值的研究结果表明 ,田间小菜蛾和绒茧蜂对甲胺磷和甲基异柳磷的抗性与 ACh E对杀虫剂的不敏感性有关。田间监测结果表明 ,每年 9月至次年 2月期间 ,由于田间杀虫剂选择压较高 ,小菜蛾 ACh E对有机磷较不敏感 ,而在每年的 6月至 8月期间 ,ACh E敏感性有所升高 ,达到全年的最高点。寄生于同一虫源的绒茧蜂 ACh E敏感性的变化也呈明显的相关性。绒茧蜂 ACh E的敏感性显著高于小菜蛾 ,尚未达到高度不敏感水平。当田间选择压极高时 ,可导致小菜蛾 ACh E呈高度不敏感 ,此时绒茧蜂 ACh E也表现出较高的不敏感性。     

多杀菌素对菜蛾绒茧蜂的致死和亚致死效应

以对多杀菌素高抗的小菜蛾纯合子品系作寄主饲养菜蛾绒茧蜂,用多杀菌素田间推荐使用浓度(25 mg/L)分别处理处于卵期、幼虫期和蛹期的绒茧蜂,其中卵期和幼虫期通过处理寄主幼虫间接处理,并测定该药剂对成虫的毒力,系统观察该杀虫剂对绒茧蜂各虫期的致死和亚致死作用。与对照相比,绒茧蜂卵期或幼虫期其寄主受药后,可导致蜂幼虫死于寄主体内或啮出寄主的过程中,使结茧化蛹率下降43% ~56%,成虫羽化率下降19% ~33%,成蜂雌性比下降11% ~25%,而成虫大小、寿命和寄生力未受显著影响;在蛹期受药使成虫羽化率下降10%,成蜂寿命缩短,但对成虫寄生力无显著影响;对成虫24 h的LC99为4.31 mg/L。结果表明,多杀菌素可进入寄主作用于其体内的蜂卵和幼虫,或直接作用于蜂蛹和成虫,从而对绒茧蜂各个虫态产生显著的致死和亚致死效应,尤以对成虫高毒。     

Inoculation

Terpenes and biogenically related phenols commonly found in plant essential oils are known to be toxic to insect pests. Accordingly thymol was tested for acute toxicity via topical application to diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) and its parasitoid, Cotesia plutellae (Kurdjunov) (Hymenoptera: Braconidae under laboratory conditions. Topical application to adult female parasitoids versus second instars of P. xylostella showed that thymol was about 62 times less toxic to the parasitoid than to the host larvae with 24 h LD₅₀ of 0.052 and 0.0008M, respectively. Although thymol was less toxic to the parasitoid, some biological parameters of the progeny at sublethal doses of surviving parasitoids were impaired such as rate of emergence and development time of larvae and pupae. The impact on detoxification enzymes was also studied and there was no significant induction in cytochrome P450 and carboxylesterase activities in both treated male and female wasps. Results obtained suggest that parasitoid is able to withstand the impact of thymol significantly.