Insecticide susceptibility and resistance of Blattella germanica (Blattaria: Blattellidae) in Seoul, Republic of Korea, 2007

The susceptibility of Blattella germanica (L.) in the Republic of Korea (ROK) to insecticides was evaluated under laboratory conditions using 12 insecticides currently used by the local public health centers and/or pest control operators in the ROK. The insecticides included seven pyrethroids and five organophosphates. Based on their LD₅₀ values, the order of susceptibility of B. germanica adults to the insecticides was chlorpyrifos-methyl, profenofos and chlorpyrifos with values of 0.07, 0.29 and 0.88 µg/♀, respectively. The least susceptibility was obtained with tetramethrin at LD₅₀ of 7.39 µg/♀. In the comparative resistance test, the resistance ratios (RR) of 12 insecticides were compared to each other using field-collected B. germanica adults in Seoul between 1993 and 2007. Blattella germanica demonstrated higher RRs to pyrethroids such as λ-cyhalothrin, and low RRs among the organophosphates. Among the pyrethroids, λ-cyhalothrin had the highest RRs of 111- and 129-fold differences at LD₅₀ and LD₉₀ values, respectively. Among the organophosphates, profenofos was observed to have the highest RRs of 4- and 15-fold differences at LD₅₀ and LD₉₀ values, respectively. However, there were no significant differences in susceptibility to tetramethrin, chlorpyrifos and fenitrothion. Blattella germanica was more susceptible to pyridafenthion showing a 0.7-fold difference in a resistance ratio (RRLD₅₀= LD₅₀ value of 2007/LD₅₀ value of 1993). Resistance ratio of tetramethrin was low, but susceptibility was also not high.     

A microdialysis study of allatostatin degradation in Blattella germanica (L.) (Dictyoptera, Blattellidae)

Allatostatins with a typical C‐terminal sequence YXFGL‐NH₂ are insect neuropeptides with inhibitory properties upon Juvenile Hormone production in the corpora allata, vitellogenin release by the fat body, and gut and dorsal vessel motility. All these biological effects are rapidly reversible, suggesting the occurrence of effective mechanisms for inactivation of the peptides. We have studied the degradation of DRLYSFGL‐NH₂ (BLAST‐2), one of the allatostatins of Blattella germanica, in the internal milieu of adult females of this cockroach. The experimental approach combined the use of the radioiodinated derivative [¹²⁵I‐Tyr⁴]BLAST‐2, microdialysis techniques and HPLC analysis with a radioisotope detector. Under these experimental conditions, the half‐life of BLAST‐2 in the internal milieu of the adult female of B. germanica was between 3 and 6 min. Such a short half‐life explains the high doses of allatostatins required to obtain the expected biological effects when tested in vivo, and suggests that circulating allatostatins are subject to rapid rates of synthesis and degradation in order to be operative physiologically.     

Biochemical characterization and purification of esterases from three strains of German cockroach,Blattella germanica (Dictyoptera: Blattellidae)

Three strains of German cockroach, Blattella germanica (L.) showed varying levels of resistance to chlorpyrifos, methyl parathion, propoxur, bendiocarb, and cypermethrin. The general esterase activity was at least twofold higher than susceptible strain. The subcellular distribution studies revealed that the majority of the esterase activity is present in the 100,000g cytosolic fraction. Only a small portion of the activity was membrane bound. Using non-denaturing gel electrophoresis, ten isozymes were identified in German cockroaches. These isozymes were isolated individually from the gels and analyzed for differences in activity. The isozymes E5, E6, and E7 of resistant strains had significantly higher specific activities when compared with the susceptible strain. The purification process using various column chromatography and preparative gel electrophoresis resulted in 9–11% of total esterase recovery. About double the amount of E6 was recovered from the resistant strains when compared with the susceptible strain. Kinetic analyses of E6 did not indicate differences in K_m and V_max values between the resistant and susceptible strains. Also, inhibition of esterase activity by paraoxon, chlorpyrifos, and propoxur did not suggest any structural differences in esterase E6 between strains. The results suggest that the increased production of E6 esterase contributes to insecticide resistance in German cockroaches. The role of E6 may be sequestration of toxic molecules rather than hydrolysis. © 1996 Wiley-Liss, Inc.     

德国小蠊抗药性机理

德国小蠊(Blattella germanica)是一种重要的室内卫生害虫,化学防治是目前主要的防治手段,但抗药性已逐渐成为制约德国小蠊防治的关键因素。德国小蠊抗药性的产生存在多种机理,本文从行为抗性、表皮穿透性降低、代谢抗性、靶标抗性及微生物降解等方面对德国小蠊抗药性产生机理进行了综述,重点阐述了近年来德国小蠊抗药性机理最新的研究进展。     

Aspergillosis in German cockroach Blattella germanica (L.) (Blattoidea: Blattellidae)

Natural infection of Aspergillus flavus was observed in adults of Blattella germanica. Though the adult insects exhibited no external symptoms, they became hypoactive and later died. The dead and experimentally infected insects repeatedly yielded Aspergillus flavus in culture on Czapek's medium. Direct microscopic observation of the tissues of infected insects revealed fungal material. The blood films stained with Giemsa stain showed granulocytes (GRs) engulfing fungal hyphae. A remarkable increase in GR and plasmatocyte (PL) counts occurred in differential haemocyte counts (DHCs) of the infected insects. Two main types of immunological responses of the insect noticed were phagocytosis and encapsulation. DHC showed maximum involvement of GRs and PLs in immune mechanism. This revised version was published online in June 2006 with corrections to the Cover Date.     

Determination of allatostatin levels in relation to the gonadotropic cycle in the female of Blattella germanica (L.) (Dictyoptera, Blattellidae)

A polyclonal antibody against the allatostatin BLAST-3 (AGSDGRLYSFGL-NH₂) of the cockroach Blattella germanica (L.) (Dictyoptera, Blattellidae) has been raised and characterized, and an ELISA (enzyme-linked immunosorbent assay) for allatostatin quantification has been developed. Allatostatin contents in brain, midgut and haemolymph have been measured in females of B. germanica during the first gonadotropic cycle. Brain allatostatin content increases steadily from adult emergence to the formation of the first ootheca. The values range from 2 ng/brain on the day of adult emergence to 25 ng/brain when the insect forms the ootheca 8 days later. In the midgut, the pattern is similar but the values are about half those of the brain. Allatostatin concentrations in the haemolymph after HPLC separation are in the nanomolar range. The occurrence of allatostatins in the haemolymph suggests that these peptides can act through a humoral pathway, as well as via nerves. The allatostatin content of both brain and midgut are high while the female is transporting the ootheca, which suggests that these peptides could be related to the low metabolic status characterising the period of oothecal transport.     

Calling behavior of the female german cockroach,Blattella germanica (Dictyoptera: Blattellidae)

Virgin German cockroach females, Blattella germanica(L.), were observed, for the first time, to exhibit a characteristic calling behavior during which females emit a volatile sex pheromone. Under a photoperiod of 12L12D, the percentage of 7-day-old virgin females that exhibited this behavior peaked before the end of the scotophase in a similar pattern to the diel periodicity of mating. A clear relationship was evident between calling and stages of sexual receptivity during successive gonotrophic cycles. Females initiated calling 5–6 days after the imaginal molt, when their basal oocytes were 1.6 mm long. If not mated, females continued to exhibit bouts of calling during the next 3–4 days until 24 h before ovulation. Calling was completely suppressed by mating as well as the presence of an egg case in the genital atrium in both virgin and mated gravid females. We suggest that calling and the emission of a volatile sex pheromone serve to attract males from a distance as well as to potentiate responses to contact sex pheromone in aggregations.     

Effects of ovariectomy and mating on the activity of the corpora allata in adult female Blattella germanica (L.) (Dictyoptera: Blattellidae)

In adult female cockroaches, the ovary greatly affects the synthesis of Juvenile Hormone (JH) by the corpora allata, and in females of some cockroach species, removal of the ovaries results in a permanent depression of JH synthesis. We report that the corpora allata in ovariectomised, adult virgins of the German cockroach, Blattella germanica (L.), increase and then decrease in activity, as they do in intact females. Moreover, the distal tubules in the left colleterial glands of ovariectomised females accumulate abundant protein, the production of which is regulated by JH. In both ovariectomised and sham‐operated females, the activity of the corpora allata more than tripled between days 1 and 4 of adulthood, during which the oöcytes of sham‐operated females grew considerably in length. The corpora allata of sham‐operated females produced even more JH on day 7, but very little on day 10, by which time all females had oviposited. The glands of ovariectomised females, by constrast, produced a similar amount of JH on day 7 as on day 4, but much less on day 10. Beginning on day 13, the activity of the corpora allata increased again in ovariectomised females, an increase that did not occur until day 22 in sham‐operated females. Mating of ovariectomised females on day 6 resulted in a significant increase in the activity of the corpora allata by day 10. We conclude that both the ovary and mating stimulate the synthesis of JH early in the reproductive cycle, but that neither is needed for the occurrence of a complete cycle of JH synthesis.     

Permethrin resistance ratios compared by two methods of testing nymphs of the German cockroach, Blattella germanica

For the German cockroach, Blattella germanica L. (Dictyoptera: Blattellidae), the permethrin resistance ratio (RR) was assessed by topical application and by tarsal contact tests, using first-instar nymphs of five strains from Tehran, Iran. Each test was replicated three or four times with 10 nymphs aged 2-3 days; mortality was scored 24h post-treatment. The reference susceptible strain showed LD50 permethrin 0.0175 microl/nymph from topical application, KT50 of 8.41 min and LT50 of 12.82 following tarsal contact with permethrin 15 mg/m2. In four wild strains (F1 generation) the RR varied from 4.14 to 4.7 for mortality after topical application, from 4.2 to 6.45 for mortality and 17-27 for knockdown following tarsal contact tests. Hence, overall knockdown results gave much higher RRs than for mortality data. Resistance ratios based on both methods of treatment were very similar: one strain showed a slightly higher value by topical application (RR 4.6 vs. 4.2, i.e. 1.1-fold difference) whereas the other three strains gave slightly greater RR (1.2-1.4 fold) by tarsal contact. Resistance was abolished by cotreatment with the synergist piperonyl butoxide plus permethrin (ratio 3:1 required for full efficacy), indicating that mixed-function oxidases were inhibited as a major metabolic pathway in all four resistant strains.     

Insecticide Susceptibility of Field‐collected Blattella germanica (Blattaria: Blattalidae) in Busan,Republic of Korea during 2014

The susceptibility values for field‐collected (BG‐BG) and laboratory (KS‐BG) strains of German cockroaches (BS‐BG), Blattella germanica (L.) to five synthetic pyrethroid and three organophosphate insecticides were assessed by topical application. Both KS‐BG and BS‐BG strains demonstrated the highest levels of susceptibility to deltamethrin with LD₅₀ values of 0.0035 μg/female and 1.5744 μg/female, respectively. The KS‐BG strain demonstrated the lowest susceptibility level to fenthion with an LD₅₀ value of 0.0698 μg/female, while the BS‐BG field population showed the lowest susceptibility to bifenthrin with 4.6811 μg/female. The BS‐BG field population showed resistance levels of 50 to 640 fold higher against the eight pesticides evaluated compared to the KS‐BG strain. The resistance ratios (RR) of the eight pesticides were compared using populations of B. germanica that were collected from the same locality during 2007 and 2014. The field population of B. germanica collected during 2014 demonstrated significantly high resistance to an organophosphates and all pyrethroids when compared with those collected during 2007, but RR values were <10 except for chlorpyrifos‐methyl and chlorpyrifos with RR values of 74 and 104, respectively.     

Isolation and sequence of a partial vitellogenin cDNA from the cockroach,Blattella germanica (L.) (Dictyoptera,Blattellidae), and characterization of the vitellogenin gene expression

A partial cDNA clone of the vitellogenin gene from the cockroach Blattella germanica has been isolated from a cDNA expression library using an anti-vitellin–vitellogenin antiserum probe. The analysis of cDNA inserts gave a sequence of 2,645 nucleotides corresponding to the 3′ region. The deduced amino acid sequence is 825 residues long and is similar to the homologous portion of the vitellogenin of other insect species, especially that of the mosquito Aedes aegypti. RNA hybridization studies indicated that the vitellogenin gene expression is limited to the fat body of adult females. The pattern of expression during the first vitellogenic cycle was approximately parallel to that of vitellogenin production by the fat body previously described. The availability of a cDNA probe for the B. germanica vitellogenin gene represents a useful tool to study the molecular action of hormones affecting vitellogenin synthesis in this species. Arch. Insect Biochem. Physiol. 38:137–146, 1998. © 1998 Wiley-Liss, Inc.     

Distribution of Oriental and German cockroaches, Blatta orientalis and Blattella germanica (Dictyoptera), in the United Kingdom

Results are presented of a survey carried out by Rentokil Ltd on the distribution of the Oriental cockroach Blatta orientalis L. and the German cockroach Blattella germanica L. in the United Kingdom. The known ranges of both species are increased considerably by the findings of the survey, with several new vice-county records for Scotland (including the Western Isles), England and Wales. The frequency at which Blatta orientalis was observed in outdoor habitats may indicate that this species sometimes spreads to new areas without human assistance.     

饵料蛋白质水平对德国小蠊营养效应及氮代谢的影响

【目的】本研究旨在探究饵料蛋白质水平对德国小蠊Blattella germanica营养利用及氮代谢的影响,为蟑螂毒饵的研发提供新思路。【方法】采用标准重量分析法评估了取食4种不同蛋白质水平(5%, 25%, 45%和65%)饵料的德国小蠊雄成虫营养效率指数和氮利用率;利用分光光度法测定了取食不同蛋白水平饵料的德国小蠊雄成虫体内黄嘌呤氧化酶(xanthine oxidase, XOD)、谷草转氨酶(glutamic oxaloacetic transaminase, GOT)、谷丙转氨酶(glutamic pyruvic transaminase, GPT)活性及尿酸含量。【结果】取食65%蛋白质饵料组的德国小蠊雄成虫的相对取食量最高,而取食45%蛋白质饵料组的雄成虫食物利用率、食物转化率及相对生长率均显著高于取食5%和65%蛋白质饵料组的雄成虫。且德国小蠊雄成虫体内氮、粪便氮、氮消耗速率、氮排泄率、氮生成率、氮同化效率、黄嘌呤氧化酶活性和尿酸含量均随饵料蛋白质水平的提高而提高,但65%蛋白质饵料组氮利用率最低,45%蛋白质饵料组谷草转氨酶活性最高,25%和45%蛋白质饵料组谷丙转氨酶活性显著高于5%和65%蛋白质饵料组。【结论】适量蛋白质饵料有利于德国小蠊对食物及氮的利用,而高蛋白质含量条件下德国小蠊谷草转氨酶和谷丙转氨酶活性下降,说明高蛋白不利于德国小蠊利用食物,且增加其代谢负担。     

海葵毒素Av3对德国小蠊的毒性及其作用机制

摘要: 【目的】Ⅲ型海葵毒素(Av3)对昆虫具有显著的选择性毒性,对其作用机制的研究对新型高选择性毒性杀虫剂的设计研究具有重要意义。【方法】反向高效液相色谱及电喷雾质谱用于鉴定化学合成的Av3野生型(Av3 wild type, Av3-WT)及其突变体的纯度和分子量;生物活性测定检测Av3-WT及其突变体对德国小蠊Blattella germanica成虫的毒力;双电极电压钳技术检测Av3-WT及其突变体对德国小蠊钠通道BgNav1-1a失活的抑制作用。构建基于BgNav1-1a与大鼠钠通道rNav1.2a的重组嵌合体,通过双电极电压钳技术确定BgNav1-1a上参与Av3-WT选择性毒性的关键区域。【结果】芳香族氨基酸Y7, W8和Y18分别突变后形成的Av3-WT突变体Y7A, W8A和Y18A对德国小蠊成虫的毒力显著降低,半数击倒剂量(KD50)与Av3-WT相比均增加了超过10倍;与Av3-WT对通道失活62%的抑制率相比,250 nmol/L的毒素突变体Y7A, W8A和Y18A对BgNav1-1a失活的抑制作用也显著降低,通道失活的抑制率分别降低到12%, 23%和8%;以rNav1.2a胞外环DI/SS5-S6替换BgNav1-1a的相应序列获得的重组嵌合体钠通道对Av3-WT毒素的敏感性几乎丧失,仅3.6%的通道在1 μmol/L Av3-WT作用下失活被抑制。BgNav1-1a胞外环 DI/SS2-S6上的His404突变为Tyr后几乎丧失对毒素的敏感性,仅6%的通道在1 μmol/L Av3-WT作用下失活被抑制。【结论】芳香族氨基酸Tyr7, Trp8和Tyr18参与到构成Av3-WT分子的生物活性表面;钠离子通道胞外环DI/SS2-S6是影响Av3-WT毒素发挥选择性的关键结合区域,BgNav1-1a的DI/SS2-S6上的His404则是影响Av3-WT选择性毒性的关键氨基酸。     

Experimental aspergillosis in the German cockroach Blattella germanica: a histopathological study

Inoculation of a spore suspension of Aspergillus flavus in the haemocoel of the German cockroach (Blatella germanica) resulted in large-scale invasion of various internal organs as seen in tissue sections stained with a fungal stain. The organs affected were the alimentary canal, fat bodies, muscle fibres, malpighian tubules and the cerebral neurosecretory cells. No invasion of the trachea and tracheoles was noted. This revised version was published online in June 2006 with corrections to the Cover Date.     

德国小蠊两个海藻糖合成酶基因的克隆、组织分布及温度诱导表达分析

【目的】海藻糖合成酶（trehalose-6-phosphate synthase, TPS）是参与昆虫血糖-海藻糖合成的关键酶。本研究旨在克隆德国小蠊 Blattella germanica TPS基因,研究TPS基因在德国小蠊不同组织中的表达模式及在不同温度处理下的表达情况。【方法】通过RACE技术克隆德国小蠊TPS基因全长序列,利用荧光定量PCR的方法检测TPS基因在德国小蠊5龄幼虫不同组织中的表达模式及在高温(40℃和46℃处理30 min)及低温(0℃和10℃处理1 h)逆境下的表达量变化。【结果】从德国小蠊中克隆获得2个TPS基因,分别命名为 BgTPS1 (GenBank登录号：KR050213) 和 BgTPS2 (GenBank登录号：KR050214)。其中,BgTPS1基因cDNA序列全长2 987 bp,开放阅读框 (ORF) 2 502 bp,编码833个氨基酸;BgTPS2基因cDNA序列全长3 212 bp,开放阅读框2 469 bp,编码822个氨基酸。BgTPS1和BgTPS2基因都主要在5龄幼虫脂肪体中表达,且BgTPS2基因的表达量为BgTPS1基因表达量的3.9倍。在两种不同极端温度诱导下,BgTPS1和BgTPS2基因mRNA均上调表达。其中,BgTPS2 的表达量始终显著高于 BgTPS1。在0℃时,BgTPS1和BgTPS2的表达量最高。【结论】德国小蠊5龄幼虫中存在2个TPS基因。两个TPS基因均在脂肪体中高表达,且BgTPS2基因的表达量显著高于BgTPS1基因;低温和高温诱导下均能促进两个基因的表达量上升。该结果为进一步明确昆虫海藻糖的合成途径及其在昆虫对温度逆境的反应中的作用研究奠定了基础。     

Effect of the synergist, piperonyl butoxide, on the development of deltamethrin resistance in yellow fever mosquito, Aedes aegypti L. (Diptera: Culicidae)

The larvae and adults of Aedes aegypti were tested for the potential to develop resistance to the synthetic pyrethroid, deltamethrin, alone or a combination of deltamethrin with the synergist, piperonyl butoxide (PBO). Although continuous larval selection for 40 generations resulted in 703-fold resistance, the resistance ratio in the adults was only 1.3. Similarly, adult selections with deltamethrin showed a resistance ratio of less than four after 40 generations, indicating differential response to deltamethrin selection in the two developmental stages of the insect. When the susceptible larvae were subjected to selection pressure of deltamethrin and PBO in the ratio of 1:5 for 20 generations, the speed of selection for deltamethrin resistance slowed down by 60%. The F24 larvae obtained from the strain selected with deltamethrin alone were further subjected to selection pressure with synergized deltamethrin, which resulted in 89% reversal in deltamethrin resistance in just one generation. However, long-term selection with the insecticide-synergist combination returned resistance close to original levels in 15 generations. The data indicate the involvement of cytochrome P450-dependent detoxification as the primary mechanism of development of resistance to deltamethrin in the larvae. Implications of the results on the management of larval and adult stages of Ae. aegypti are discussed.     

Monitoring for insecticide resistance in field-collected populations of Blattella germanica (Blattaria: Blattellidae)

Seven field-collected populations of German cockroach, Blattella germanica (L.) (ICN, DNH, CHN, DGU, BSN, GSN, and GWJ), were tested for susceptibility to eight different insecticides by a topical application method, and were compared to an insecticide-susceptible KSS strain. Marked regional variations of insecticide susceptibility were observed. Extremely high to high levels of resistance were observed in bifenthrin [resistance ratio (RR), 46–159], deltamethrin (RR, 61–160), and esfenvalerate [RR, 70–270; except for BSN females (RR, 20) and GSN females (RR, 24)]. Low to moderate levels of resistance were observed in cypermethrin [RR, 16–29; except for DGU females (RR, 88) and BSN females (RR, 41)], permethrin [RR, 11–39; except for DNH females (RR, 110) and BSN females (RR, 44)], chlorpyrifos [RR, 2–13; except for GSN and GWJ females (RR, ca. 140)], chlorpyrifos-methyl (RR, 2–8), and fenthion (RR, 8–17). All of the colonies were susceptible to one or more of the insecticides examined. These results indicate that careful selection and rotational use of these insecticides should result in continued satisfactory control against field populations of German cockroach.     

Laboratory and field evaluation of Beauveria bassiana bait against two cockroach species (Dictyoptera: Blattellidae,Blattidae) in Jinan City,East China

A Beauveria bassiana bait formulation was evaluated for its efficacy in the laboratory and field against German cockroaches, Blattella germanica (L.), and American cockroaches, Periplaneta americana (L.). The LT₅₀ values were 46 and 119?h, respectively, for B. germanica and P. americana. The cockroach species were lured and killed effectively when linear distance was about 5?m between B. bassiana bait and fresh mouse food. In the field, more than 90% relative decline in density was found 14?d after treatment, which lasted for 90?d. In conclusion, laboratory and field studies demonstrated the high efficacy of a B. bassiana bait formulation against common cockroach species.