European populations of Diabrotica virgifera virgifera are resistant to aldrin,but not to methyl‐parathion

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of cultivated corn in North America and has recently begun to invade Europe. In addition to crop rotation, chemical control is an important option for D. v. virgifera management. However, resistance to chemical insecticides has evolved repeatedly in the USA. In Europe, chemical control strategies have yet to be harmonized and no surveys of insecticide resistance have been carried out. We investigated the resistance to methyl‐parathion and aldrin of samples from nine D. v. virgifera field populations originating from two European outbreaks thought to have originated from two independent introductions from North America. Diagnostic concentration bioassays revealed that all nine D. v. virgifera field populations were resistant to aldrin but susceptible to methyl‐parathion. Aldrin resistance was probably introduced independently, at least twice, from North America into Europe, as there is no evident selection pressure to account for an increase of frequency of aldrin resistance in each of the invasive outbreaks in Europe. Our results suggest that organophosphates, such as methyl‐parathion, may still provide effective control of both larval and adult D. v. virgifera in the European invasive outbreaks studied.     

Trade‐off between thermal tolerance and insecticide resistance in Plutella xylostella

Fitness costs associated with resistance to insecticides have been well documented, usually at normal temperature conditions, in many insect species. In this study, using chlorpyrifos‐resistant homozygote (R_R) and chlorpyrifos‐susceptible homozygote (S_S) of resistance ace1 allele of Plutella xylostella (DBM), we confirmed firstly that high temperature experience in pupal stage influenced phenotype of wing venation in insecticide‐resistant and insecticide‐susceptible Plutella xylostella, and S_S DBM showed significantly higher thermal tolerance and lower damages of wing veins under heat stress than R_R DBM. As compared to S_S DBM, R_R DBM displayed significantly lower AChE sensitivity to chlorpyrifos, higher basal GSTs activity and P450 production at 25°C, but higher inhibitions on the enzyme activities and P450 production as well as reduced resistance to chlorpyrifos under heat stress. Furthermore, R_R DBM displayed significantly higher basal expressions of hsp69s, hsp72s, hsp20, hsp90, Apaf‐1, and caspase‐7 at 25°C, but lower induced expressions of hsps and higher induced expressions of Apaf‐1, caspase‐9, and caspase‐7 under heat stress. These results suggest that fitness costs of chlorpyrifos resistance in DBM may partly attribute to excess consumption of energy caused by over production of detoxification enzymes and hsps when the proteins are less demanded at conducive environments but reduced expressions when they are highly demanded by the insects to combat environmental stresses, or to excess expressions of apoptotic genes under heat stress, which results in higher apoptosis. The evolutionary and ecological implications of these findings at global warming are discussed.     

家用调料植物粗提物防治小菜蛾的研究

以安全性和简易性为前提的庭园害虫防治成为休闲生活不可或缺的技术。本文以花椒Zanthoxylum bungeamtm、八角茴香lUicium veturn、辣椒Capsicum frutescens等日用品为材料,研究了不同种类、浓度和作用时间对小菜蛾Plutella xylostella这一重要庭园害虫的拒食、触杀及产卵忌避效果。拒食试验表明,供试3种植物对小菜蛾有显著拒食作用,拒食率从大到小依次为八角茴香（0．94）、花椒（0．86）、辣椒（0．76）;拒食率随处理时问长短变化的差异不显著,但随提取液浓度的升高而升高。触杀试验表明,供试3种植物对小菜蛾有显著触杀作用,24h内死亡率从大到小依次为花椒（45．6％）、八角茴香（35．6％）、辣椒（23．3％）,均显著高于对照处理的1．1％;触杀死亡率随虫龄的增加而降低。产卵忌避试验表明,3种植物对小菜蛾成虫产卵忌避作用由大到小依次为辣椒、八角茴香、花椒。综合本研究所得结果来看,八角茴香对小菜蛾的控制效果最好。所选材料容易获得,对小菜蛾忌避作用明显,在庭园小菜蛾防治中具有潜在的应用价值。     

Molecular cloning and expression profiles of calreticulin gene from the diamondback moth,Plutella xylostella

Calreticulin (CRT) plays pivotal roles in Ca²⁺ homeostasis, molecular chaperoning, infection, inflammation and innate immunity. In an attempt to study the involvement of CRT in innate immunity, the full-length cDNA of calreticulin (PxCRT) was cloned from the diamondback moth, Plutella xylostella. It consists of 1674 bp (excluding poly-A tail) with a longest open reading frame (ORF) of 1197 bp encoding 398 amino acids. In silico analysis of PxCRT ORF reveals that it has various repeat motifs and endoplasmic reticulum retention signal found in all the calreticulin proteins. As expected, high amino acid sequence identities were found from other CRTs identified from Bombyx mori (87%), Galleria mellonella (87%), Apis mellifera (74%), Anopheles gambiae (74%), Tribolium castaneum (73%), Culex quinquefasciatus (73%), Rhodnius prolixus (72%), Nasonia vitripennis (71%), Drosophila melanogaster (71%) and Haemaphysalis qinghaiensis (68%). During development, P. xylostella expressed PxCRT predominantly in the pupal stage. In addition, spatial expression pattern analysis indicates that PxCRT was highly expressed in the silk gland. PxCRT mRNA, furthermore, was strongly induced 3 to 6 h after laminarin treatment, suggesting that PxCRT appears to be involved in immune responses and also plays an important role in the silk gland.     

Ultrastructural and functional characterization of circulating hemocytes from Plutella xylostella larva: Cell types and their role in phagocytosis

The hemocytes of different types encountered in the diamondback moth Plutella xylostella larvae of each instar and the development of the differential hemocytes counts were herein presented. Hemocytes classes/populations characterized based on their affinity with fluorescent dye (acridine orange) and ultrastructural differences comprised the prohemcoytes (<10–16%), plasmatocytes (22–65%), granulocytes (25–72%), oenocytoids (<1–9%), and spherulocytes (<1%). Prohemcoytes were the smallest cells with a comparatively tremendous nucleus. Plasmatocytes and granulocytes occupied the main proportion of total cell numbers. Oenocytoids were in a most stable presence, i.e. rotund in a diameter of 10 μm and with a nucleus deviated from the central location; however, sometimes with two nuclei which were adjoining with each other. Spherulocytes were rare and only could be observed occasionally. Ultrastructural investigation revealed that hemocytes in the diamondback moth larvae were of the typical model as in the Lepidoptera insect larvae. It is interesting to find that the cell which could phagocytize bacteria in vitro was granulocyte, not the other types of hemocytes, although plasmatocyte was usually declared to participate in this reaction in various previous studies.     

Synergism and redundancy in a plant volatile blend attracting grapevine moth females

A flight tunnel study was done to decipher the behavioral effect of grape odor in grapevine moth Lobesia botrana. A blend of 10 volatile compounds, which all elicit a strong antennal response, attracts mated grapevine moth females from a distance, by upwind orientation flight. These 10 grape volatiles are in part behaviorally redundant, since attraction to a 3-component blend of beta-caryophyllene, (E)-beta-farnesene and (E)-4,8-dimethyl-1,3,7-nonatriene was not significantly different from the 10-component blend. Blending these three compounds had a strong synergistic effect on female attraction, and omission of any one compound from this 3-component blend almost abolished attraction. It was nonetheless possible to substitute the three compounds with the other grape volatiles which are perceived by the female antenna, to partly restore attraction. Several blends, of varying composition, elicited significant attraction. The observed behavioral plasticity in response to grape volatile blends probably reflects the variation of the natural plant signal, since females oviposit on different grape varieties, in different phenological stages.     

A putative protein translation inhibitory factor encoded by Cotesia plutellae bracovirus suppresses host hemocyte-spreading behavior

An endoparasitoid, Cotesia plutellae (Hymenoptera: Braconidae), possesses a mutualistic bracovirus (CpBV), which plays significant roles in the parasitized host, Plutella xylostella (Lepidoptera: Plutellidae). CpBV15beta, a viral gene encoded by CpBV, is expressed at early and late parasitization periods, suggesting that it functions to manipulate the physiology of the parasitized host. This paper reports a physiological function of CpBV15beta as an immunosuppressive agent. The effect of CpBV15beta on cellular immunity was analyzed by assessing hemocyte-spreading behavior. Parasitization by C. plutellae caused altered behavior of hemocytes of P. xylostella, in which the hemocytes were not able to attach and spread on glass slides. CpBV15beta was expressed in Sf9 cells using a baculovirus expression system and purified from the culture media. When hemocytes of nonparasitized P. xylostella were incubated with purified CpBV15beta protein, spreading behavior was impaired in a dose-dependent manner at low micro-molar range. This inhibitory effect of CpBV15beta could also be demonstrated on hemocytes of a non-natural host, Spodoptera exigua. CpBV15beta protein significantly inhibited F-actin growth of hemocytes in response to an insect cytokine. Similarly, cycloheximide, a eukaryotic translation inhibitor, strongly inhibited the spreading behavior and F-actin growth of P. xylostella hemocytes. Under in vitro condition, hemocytes of nonparasitized P. xylostella released proteins into the surrounding medium. Upon incubation of hemocytes with either CpBV15beta or cycloheximide, their ability to release protein molecules was markedly inhibited. This study suggests that CpBV15beta suppresses hemocyte behavior by inhibiting protein translation.     

Effects of venom/calyx fluid from the endoparasitic wasp Cotesia plutellae on the hemocytes of its host Plutella xylostella in vitro

Crude venom and calyx fluid from Cotesia plutellae (Hymenoptera Braconidae) were assayed for biological activity toward hemocytes of Plutella xylostella (Lepidoptera Plutellidae). Venom from C. plutellae displayed high activity toward the spreading of plasmatocytes of P. xylostella early in the incubation period, and the inhibition was more severe as the concentration of venom increased. However, most inhibited hemocytes spread normally after being incubated for 4h. No effects were found toward granular cells from the host. Additionally, the venom from C. plutellae had some lethal effects on hemocytes of P. xylostella at high concentrations. In contrast, when incubated with different concentrations of calyx fluid, the spreading of some hemocytes was inhibited, some began to disintegrate, and some were badly damaged with only the nucleus left. After 4h, the majority of hemocytes died. The same results were observed when hemocytes were incubated in calyx fluid together with venom. These results show that calyx fluid from C. plutellae may play a major role in the suppression of the host immune system, whereas venom from C. plutellae has a limited effect on hemocytes and probably synergizes the effect of calyx fluid or polydnavirus.     

Phylogenetic analysis of two putative Nosema isolates from Cruciferous Lepidopteran pests in Taiwan

In this study, a new microsporidian, PX2, was isolated from the diamondback moth, Plutella xylostella, and then compared with another isolate (PX1), and with Nosema spodopterae and N. bombycis. Sequence data showed that the rRNA gene organizations of PX1 and PX2 exhibited a typical Nosema-specific organization: 5'-LSUrRNA (large subunit ribosomal RNA)-ITS (internal transcribed spacer)-SSUrRNA-IGS (intergenic spacer)-5S-3'. Phylogenetic analysis (maximum likelihood, neighbor joining, maximum parsimony, and Bayesian analysis) of the LSUrRNA and SSUrRNA gene sequences, and the sequences of the alpha-tubulin, beta-tubulin, and RPB1 (DNA dependent RNA polymerase II largest subunit) genes found that PX1 was closer to N. bombycis and N. spodopterae than to PX2. Comparison of the identities of the rRNA domains and of the other three genes showed a high divergence in the sequences of the rRNA spacer regions (ITS and IGS). This is consistent with the hypothesis that PX2, if not PX1, might represent a new Nosema species.     

蝉拟青霉孢子粉对小菜蛾的致病性试验

试验采用蝉拟青霉(Paecilomyces cicadae)孢子粉处理小菜蛾Plutella xylostella L.幼虫,结果表明,蝉拟青霉可以在小菜蛾幼虫和蛹上寄生,并导致小菜蛾死亡。室内试验,蝉拟青霉对小菜蛾的致死率高达96.55%;田间试验,1.6×107个/mL浓度的022017#蝉拟青霉防治小菜蛾的校正死亡率可达75.86%。该结果可用于蝉拟青霉新型真菌杀虫剂的研制。