Search

Abstract Background The overuse of antibiotics has led to lethal multi-antibiotic-resistant microorganisms around the globe, with restricted availability of novel antibiotics. Compared to conventional antibiotics, evolutionarily originated antimicrobial peptides (AMPs) are promising alternatives to address these issues. The gut microbiome of Blattella germanica represents a previously untapped resource of naturally evolving AMPs for developing antimicrobial agents. Results Using the in-house designed tool “AMPidentifier,” AMP candidates were mined from the gut microbiome of B. germanica, and their activities were validated both in vitro and in vivo. Among filtered candidates, AMP1, derived from the symbiotic microorganism Blattabacterium cuenoti, demonstrated broad-spectrum antibacterial activity, low cytotoxicity towards mammalian cells, and a lack of hemolytic effects. Mechanistic studies revealed that AMP1 rapidly permeates the bacterial cell and accumulates intracellularly, resulting in a gradual and mild depolarization of the cell membrane during the initial incubation period, suggesting minimal direct impact on membrane integrity. Furthermore, observations from fluorescence microscopy and scanning electron microscopy indicated abnormalities in bacterial binary fission and compromised cell structure. These findings led to the hypothesis that AMP1 may inhibit bacterial cell wall synthesis. Furthermore, AMP1 showed potent antibacterial and wound healing effects in mice, with comparable performances of vancomycin. Conclusions This study exemplifies an interdisciplinary approach to screening safe and effective AMPs from natural biological tissues, and our identified AMP 1 holds promising potential for clinical application. Graphical Abstract Video Abstract more...

Concerns about the negative effects of traditional insecticides and increasing insecticide resistance have prompted the exploration of botanical alternatives like essential oils (EOs). The registration of biocides is a mandatory procedure, and some regions have established a special status for compounds that meet specific low-risk criteria, which includes certain EOs. This study aimed to evaluate and compare the efficacy of sixteen EOs, both registered as low-risk biocides and/or standard biocides, against the German cockroach, Blattella germanica. A topical application was performed with undiluted EOs (15 µL) on the dorsal surface of awake cockroaches. The results showed significant variations in efficacy, as follows: thyme, sweet orange, and lavender oils were the most effective, achieving 100% mortality within 24 h and a less than 30 s knockdown effect. In contrast, linseed and cottonseed oils were the least effective, resulting in 70% and 40% 24 h mortality. Remarkably, some EOs registered as low-risk biocides performed as well as the ones registered as standard biocides, suggesting that this category does not have to always be at odds with efficacy. Future research should adopt practical, application-driven approaches to ensure bioinsecticides balance performance and safety, meeting both regulatory and consumer demands. more...

Background: The German cockroach, Blattella germanica (Insecta: Blattodea, Blattellidae), which occurs widely in human buildings, is a small cockroach species. Cockroach control chemical pesticides are toxic to the environment, and it is sometimes impossible to prevent them. Controlling Blattella germanica through ultrasonic waves can be efficient and less dangerous for the environment. Methods: In this study, the repellency and lethal effect of ultrasonic waves on male and female German cockroaches was tested in a twin glass cubic chamber at laboratory condition. The wave frequencies tested ranged from 20 to 100kHz with 5kHz steps. A signal generator generated these frequencies, and the piezoelectric transmitter of these ultrasonic waves was positioned in the chamber's center on the upper side. Results: Fisher's test showed that there was the greatest repellency effect in both male and female at frequencies of 35 and 40kHz. According to the results of the regression test, the most lethal effect is at the frequencies of 40 and 75kHz. Conclusion: The operating ultrasonic frequencies investigated in this study can be used to repel and kill German cock­roaches as pests endangering human health and environment. more...

Cockroaches harbor two coexisting symbiotic systems: the obligate endosymbiont Blattabacterium cuenotii, and a complex gut microbiota. Blattabacterium is the only bacterium present in the eggs, as the gut microbiota is acquired by horizontal transmission after hatching, mostly through coprophagy. Blattella germanica, a cosmopolitan omnivorous cockroach living in intimate association with humans, is an appropriate model system for studying whether the gut microbiota is essential for the cockroach’s survival, development, or welfare. We obtained a germ-free cockroach population (i.e., containing normal amounts of the endosymbiont, but free of microbes on the insects’ surface and digestive tract). Non-significant differences with the controls were detected in most fitness parameters analyzed, except for a slight shortening in the hatching time of the second generation and a reduction in female weight at 10 days after adult ecdysis. The latter is accompanied by a decrease in uric acid reserves. This starvation-like phenotype of germ-free B. germanica suggests that the microbiota is not essential in this species for survival and development throughout its complete life cycle, but it could participate in complementation of host nutrition by helping with food digestion and nutrient absorption. more...

Penggunaan attractive toxic sugar baits (ATSB) merupakan hal baru dalam pengendalian vektor dan hama permukiman. Penelitian ini bertujuan untuk mengetahui konsentrasi umpan gula yang mampu menarik lipas jerman Blattella germanica Linnaeus dan mengetahui keefektifan berbagai jenis bahan toksik sebagai ATSB untuk mengendalikan lipas jerman. Metode ini didasarkan pada perilaku serangga dewasa yang memakan gula dari sumber yang mengandung bahan toksik yang dapat membunuh serangga tersebut. Jenis bahan toksik yang digunakan dalam penelitian ini adalah insektisida anorganik (asam borat), pirol (klorefenapir), neonikotinoid (dinotefuran), dan piretroid (permetrin dan deltametrin). Hasil penelitian menunjukkan umpan gula yang menarik untuk lipas jerman adalah sukrosa 5%. ATSB dengan bahan toksik asam borat 25% menimbulkan kematian lipas sebesar 46,25%, dan dengan bahan toksik klorfenapir 0,12% menyebabkan kematian lipas 70% pada 24 jam pascaperlakukan. Selanjutnya, ATSB dengan bahan toksik dinetofuran 0,08% dan deltametrin dalam berbagai konsentrasi menyebabkan kematian lipas tertinggi (100%), sedangkan dengan permetrin menimbulkan kematian lipas yang lebih rendah daripada ATSB dengan bahan toksik lainnya pada jam pengamatan yang sama. Penelitian ini memberikan informasi dasar tentang pemanfaatan ATSB dan potensinya dalam pengendalian lipas jerman di Indonesia. more...

Blattella germanica harbours two cohabiting symbiotic systems: an obligate endosymbiont, Blattabacterium, located inside bacteriocytes and vertically transmitted, which is key in nitrogen metabolism, and abundant and complex gut microbiota acquired horizontally (mainly by coprophagy) that must play an important role in host physiology. In this work, we use rifampicin treatment to deepen the knowledge on the relationship between the host and the two systems. First, we analysed changes in microbiota composition in response to the presence and removal of the antibiotic with and without faeces in one generation. We found that, independently of faeces supply, rifampicin-sensitive bacteria are strongly affected at four days of treatment, and most taxa recover after treatment, although some did not reach control levels. Second, we tried to generate an aposymbiotic population, but individuals that reached the second generation were severely affected and no third generation was possible. Finally, we established a mixed population with quasi-aposymbiotic and control nymphs sharing an environment in a blind experiment. The analysis of the two symbiotic systems in each individual after reaching the adult stage revealed that endosymbiont’s load does not affect the composition of the hindgut microbiota, suggesting that there is no interaction between the two symbiotic systems in Blattella germanica. more...

ObjectiveTo investigate the resistance dynamics of Blattella germanica to commonly used insecticides in Yangpu District of Shanghai during 2014‒2020， and to provide the basis for the rational use of insecticides against cockroaches.MethodsBlattella germanica was captured in two farmer’s markets in 2014， 2017 and 2020. The residual film method recommended by WHO was used to test resistance of Blattella germanica to the insecticides.ResultsIn 2014， 2017 and 2020， the resistance ratio of Blattella germanica in Yangpu District was 6.96， 4.39， 7.26 to beta-cypermethrin， 10.41， 6.71， 5.24 to permethrin， and 2.28， 3.16， 1.01 to propoxur.ConclusionThe resistance of Blattella germanica to permethrin and propoxur decreases， and the resistance to beta-cypermethrin keeps at low level. Comprehensive management and rotation of insecticides should be implemented to delay the increase of resistance. more...

The purpose of the research is studying the efficacy of "Tarzan, VE" against representatives of the Blattoptera order, Blattella germanica.Materials and methods. Experimental studies to study the efficacy of "Tarzan, VE" on representatives of the Blattoptera order were performed for two weeks at the premises of the Skryabin MVA (Moscow) and the KemSMU (Kemerovo). The study object was the red German cockroach B. germanica, a laboratory culture of which was grown in the MVA insectarium. Experiments 1 and 2 consisted of three tests of three sets each: a test to study the efficacy of the drug against cockroaches by the topical application; and a test to study the efficacy of "Tarzan, VE" against cockroaches by the forced exposure of arthropods to test surfaces, namely, plywood or glass previously treated with the drug in different concentrations. Dead insects were counted after a day.Results and discussion. We established the efficacy of "Tarzan, VE" in the form of an active substance in different dilutions against cockroaches B. germanica of both sexes using the topical application. Its efficiency decreases to 97% when diluted 1000 times (0.001N). With forced exposure to treated test surface (plywood), the efficacy of “Tarzan, VE” depended on the substance diluted: 90% at 0.01N, 83.3% at 0.005N, and 50% at 0.001N. The maximum effect of "Tarzan, VE" was observed when using the method of forced exposure of cockroaches to the treated test surface, glass. The efficacy of the drug in this case was 100% regardless of the sex and development stage of cockroaches. It was found that different concentrations of the insecticide had a toxic effect on the imago of both sexes and larval stages of cockroach development. The insecticidal nature of the drug is ensured by the use of zeta-cypermethrin as an active ingredient. "Tarzan, VE" insecticide can be recommended to control and prevent the distribution of B. germanica. more...

Cockroach species Periplaneta americana and Blattella germanica potentially survive in locations close to human activity. Besides spoiling food material, cockroaches also transfer pathogens of different diseases among human beings. Since the insecticides have been used extensively to control cockroaches, information on their insecticide susceptibility and toxicity at the cellular level may be crucial. In the study, deltamethrin toxicity as well as the deltamethrin-mediated cytomorphological changes in the brain, ovary and midgut of the two important cockroach species have been assessed. Different concentrations [0.00025% (0.0025 mg/ml), 0.0025% (0.025 mg/ml), 0.025% (0.25 mg/ml), 0.25% (2.5 mg/ml), 0.5% (5 mg/ml), 1% (10 mg/ml)] of deltamethrin in acetone were used to expose test species in WHO bottle assay. Knockdown was recorded after 5 min interval while delayed mortality was observed after 24 h. Brain, ovary and gut were dissected post 1 h exposure and 24 h holding (for 0.25, 0.5 and 1% concentration), and tissues were processed for microscopic analysis. Deltamethrin exposed cockroaches and dissected tissues were used to estimate deltamethrin using HPLC. At 0.00025% (lowest concentration), the percentage knock-down observed was 66.7% for P. americana and 80% B. germanica respectively (R2 = 0.78; p = 0.0001) in 1 h. KDT50 value was found to be 8.7 min (95% CI: 7.3–10.2), while KDT99 was 20.7 min (95% CI: 16.0–35.7) in P. americana at 1% concentration. Whereas, the KDT50 and KDT99 values for B. germanica were 7.4 min (95% CI: 5.4–9.1) and 27.4 min (95% CI: 18.2–80.0) at a similar concentration. LD50 and LD95 values (for 60 min standard exposure) were 0.0006% (95% CI: 0.00–0.001) and 0.034% (95% CI: 0.013–0.49) respectively for P. americana, while these values were 0.0005 (95% CI: 0.00–0.001) and 0.04 (95% CI: 0.01–0.23) for B. germanica. Exposure to 1% deltamethrin induced a considerable toxic effect in the epithelial cells in the midgut. HPLC estimated 0.21 ± 0.05 mg (95% CI: 0.18–0.25; CoV 23.9%) deltamethrin in P. americana post 1% exposure. Even short term exposure to a low concentration of synthetic pyrethroid deltamethrin displayed immediate knockdown and delayed mortality in both the test species. Considerable histological damage was observed in both the insects at 1% exposure. In India, resistance to deltamethrin may have been reported among different insects due to its extensive use. However, the formulations such as insecticide paints, attractant baits etc. developed using deltamethrin as an active ingredient could be useful in cockroach control operations. more...

This study aims to investigate changes in resistance to insecticides over a ten-year period in five strains of German cockroaches, Blattella germanica (Linnaeus), which had previously shown resistance to deltamethrin, propoxur, and fipronil in 2012. The five strains were reared in a laboratory without exposure to insecticides for ten years. In 2022, they were tested for resistance to the same insecticides using a topical application method. The resistance ratio (RR50) was calculated for each strain to determine the level of resistance to each insecticide. The study found that German cockroaches, initially resistant, became less resistant or even susceptible after being reared in a laboratory without insecticide exposure for over ten years. This decrease in resistance was observed in all strains, but the reduction pattern varied, apparently influenced by the type of insecticide. For instance, the MDN2 strain, which initially had a very high level of resistance (RR50: 1019.74 -fold) to deltamethrin, became susceptible (RR50: 1 -fold). Similarly, the ACH2 strain, initially classified as highly resistant to propoxur (RR50: 48.64 -fold), and the strain with high resistance (RR50: 12.21 -fold) to fipronil, both became susceptible. The study also discussed potential mechanisms for the decrease in resistance, including reduced frequency of resistance genes and fitness costs. The findings suggest that rearing German cockroaches in a laboratory without insecticide treatment can lead to a decrease in resistance to commonly used insecticides. These findings can be used to develop more effective methods for controlling German cockroaches. more...

Background: Cockroaches are one of the most common pests in many residential areas. In this study, the simultaneous effects of fungi, Metarhizium anisopliae and fenitrothion-coated baits on the mortality rate of the German cockroach nymphs were investigated. Methods: To determine the lethal level of fenitrothion insecticide, a bioassay test was performed on the last instar nymphs of the German cockroach reared at insectarium conditions. Various toxic concentrations of fenitrothion (0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.5%, and 2%) were used. Different concentrations of M. anisopliae (1×104, 1×105, 1×106, 1×107, 1×108 Conidia/ ml) were also applied to nymphs. Eventually, we combined the effective dose of fenitrothion (0.93%) with the effective concentration of M. anisopliae (6.6 ×106 Conidia/ml) to provide the fungus-coated bait to attract insects. Mortality was recorded 24–96 hours after exposure to the toxic bait. The resulting data were subjected to Probit analysis. Results: The results of applying M. anisopliae spores with fenitrothion composition showed that the mortality rate of German cockroach nymphs was significant. Therefore, the optimal dose of fenitrothion used in combination with M. anisopliae seems essential to reduce the German cockroach nymphs. Conclusion: The results of this study can be considered a suitable method as a mixture with low cost and minimal damage to the environment and other organisms. more...

Bacillus thuringiensis (Bt) is a well-known entomopathogen. In this study, we cloned the vip3Aa1 gene from Bt strain GIM1.147 and investigated the insecticidal activity of Bt Vip3Aa1 protein produced by Escherichia coli against Periplaneta americana and Blattella germanica. The results showed that purified Vip3Aa1 exhibited an LC50 at 24 h against P. americana and B. germanica of 0.182 mg·ml-1 and 0.276 mg·ml-1, respectively. Investigations of its mode of action showed that Vip3Aa1 could be proteolyzed into a 62-kDa toxic protein by P. americana gut-soluble proteases. In addition, Vip3Aa1 caused severe damage to the columnar colon and the midgut, as observed through hematoxylin-eosin staining and scanning electron microscopy. The 62-kDa activated Vip3Aa1 protein could form ion channels in the colon and the midgut in vitro. Based on protease activity analysis, Vip3Aa1 at concentrations of 0.125 mg·ml-1 and 0.031 mg·ml-1 could downregulate the activities of glutathione S-transferase, α-NA esterase, trypsin, and chymotrypsin. This report provides the first description of the activity of Vip3Aa1 toxins toward P. americana and B. germanica and demonstrates that the mechanism through which Vip3Aa1 kills P. americana and B. germanica differs from that involved in the killing of lepidopteran insects. more...

Background and Aim: As a mechanical vector of some communicable diseases and a self-adaptive species to human environments, the German cockroach can transmit pathogens, such as bacteria, viruses, and fungi, to human beings. This study was conducted to determine the toxicity of imidacloprid and chlorpyrifos against German cockroaches. Materials and Methods: In this experimental study, the last instar German cockroach nymphs were used to test their sensitivity to imidacloprid and chlorpyrifos insecticides by the contact and bait methods. In bioassay (jar test), the nymphs were isolated from the main colony and were exposed to the insecticides for 30 min. The mortality rate was recorded 24 h after the recovery time. In bioassay (bait), 24-96 h after exposure to the poisonous bait, the mortality rate was recorded and regression analysis was run to analyze the data in the SPSS software (IBM, Chicago, USA). Results: The lethal doses (LD) of imidacloprid and chlorpyrifos were 9.5 mg/m2 and 39.78 mg/m2, respectively. The LD50 for imidacloprid and chlorpyrifos were 2.66 and 9.92 mg/m2, respectively. Results revealed that the highest concentration of imidacloprid (45%) could cause the highest mortality rate (95%) 24 h after exposure. There is a significant difference in the mortality of the samples during the follow-up period. Moreover, the chlorpyrifos smeared bait, with a concentration of 16% after 24 h, had the highest mortality rate (95%). Conclusion: The highest mortality rate occurred in the ingestion of imidacloprid smeared bait within the first 48 h after being exposed to the insecticide. Therefore, the results show that imidacloprid can prove significantly effective in controlling cockroaches. more...

The burden of allergic illnesses is continuously rising, and patient diagnosis is a significant problem because of how intricately hereditary and environmental variables interact. The past three to four decades have seen an outbreak of allergies in high-income countries. According to reports on the illness, asthma affects around 300 million individuals worldwide. Identifying clinically important allergens for the accurate classification of IgE-mediated allergy respiratory disease diagnosis would be beneficial for implementing standardized allergen-associated therapy. Therefore, the current study includes an in silico analysis to identify potential IgE-mediated allergens in date palms and cockroaches. Such an immunoinformatic approach aids the prioritization of allergens with probable involvement in IgE-mediated allergic respiratory diseases. Immunoglobulin E (IgE) was used for molecular dynamic simulations, antigen–antibody docking analyses, epitope identifications, and characterizations. The potential of these allergens (Per a7, Per a 1.0102, and Bla g 1.0101) in IgE-mediated allergic respiratory diseases was explored through the evaluation of physicochemical characteristics, interaction observations, docking, and molecular dynamics simulations for drug and vaccine development. more...

Mitochondria are the leading organelle for energy metabolism. The toxic effects of environmental toxicants on mitochondrial morphology, energy metabolism, and their determination of cell fate have already been broadly studied. However, minimal research exists on effects of environmental toxicants such as pesticides on mitochondrial energy metabolism at in vitro subcellular level, particularly from an omics perspectives (e.g., metabolomics). Here, German cockroach (Blattella germanica) was fed diets with (0.01 and 0.001 mg/mL) and without abamectin, and highly purified fat body mitochondria were isolated. Swelling measurement confirmed abnormal mitochondrial swelling caused by abamectin stress. The activity of two key mitochondrial energy metabolism-related enzymes, namely succinic dehydrogenase and isocitrate dehydrogenase, was significantly affected. The metabolomic responses of the isolated mitochondria to abamectin were analyzed via untargeted liquid chromatography/mass spectrometry metabolomics technology. Fifty-two differential metabolites (DMs) were identified in the mitochondria between the 0.001 mg/mL abamectin-fed and the control groups. Many of these DMs were significantly enriched in pathways involved in ATP production and energy consumption (e.g., oxidative phosphorylation, TCA cycle, and pentose phosphate pathway). Nineteen of the DMs were typically related to energy metabolism. This study is valuable for further understanding mitochondrial toxicology under environmental toxicants, particularly its subcellular level. more...

Background: Manifestation of respiratory allergy to American cockroach (Periplaneta americana) is prominent in the subtropical and tropical areas. However, co-existing perennial indoor inhalant allergies frequently compromise clinical diagnosis of cockroach allergy, and the analysis of sensitization pattern is limited by the lack of Periplaneta allergens widely available for component-resolved diagnostics (CRD).Objective: To evaluate a collection of previously described recombinant Periplaneta allergens for CRD in cockroach allergy.Methods: A panel of nine recombinant Periplaneta allergens (Per a 1–5, 7–10) was generated, purified, and subjected to physicochemical characterization by applying circular dichroism (CD) spectroscopy, dynamic light scattering (DLS), amino acid (AA) analysis, and mass spectrometry (MS). Patients (n = 117) from India, Korea, Venezuela, and Iran, reporting perennial respiratory indoor allergies with IgE sensitization to cockroach (P. americana and/or Blattella germanica), were included. The sensitization profile was monitored by the experimental ImmunoCAP testing.Results: ImmunoCAP testing confirmed IgE sensitization to Periplaneta and/or Blattella extract in 98 of 117 patients (r = 0.95). Five out of 117 patients were sensitized to only one of the two cockroach species. Within the whole study group, the prevalence of sensitization to individual allergens varied from 4% (Per a 2) to 50% (Per a 9), with the highest IgE values to Per a 9. Patients from four countries displayed different sensitization profiles at which Per a 3 and Per a 9 were identified as major allergens in India and Korea. Periplaneta-derived lipocalin and myosin light chain were characterized as new minor allergens, designated as Per a 4 and Per a 8. Periplaneta extract showed higher diagnostic sensitivity than all individual components combined, suggesting the existence of allergens yet to be discovered.Conclusion: Utilization of a panel of purified Periplaneta allergens revealed highly heterogeneous sensitization patterns and allowed the classification of lipocalin and myosin light chain from Periplaneta as new minor allergens. more...

Laboratory bioassay studies were conducted to determine the effects of 9 isolates of Beauveria bassiana and one isolate of Metarhizium anisopliae, isolated from the soils in Isparta, Turkey, against Helicoverpa armigera (Hübner), Spodoptera littoralis (Hübner) (Lepidoptera: Noctuidae), Tenebrio molitor (L.) (Coleoptera: Tenebrionidae) and Blattella germanica (L.) (Blattodea: Blattellidae). Concentrations of 2x107 conidia/mL were applied on insects by hand sprayer. All treated insects were incubated at 26±1°C, 70±5% relative humidity for 12 days. All entomopathogenic fungi were infectious to all tested insects but infection rates were different. Isolates of B. bassiana and M. anisopliae showed very low infection rates on B. germanica (3.3-6.7%). Other insects had different mortality rates. H. armigera, S. littoralis and T. molitor had 53.3-73.3%, 56.7-66.7% and 73.3-80.0% infection rates, respectively. As all fungal isolates were not very effective on B. germanica under laboratory conditions but showed effectiveness on other insects. more...

The effect of Match and Nomolt has been studied on total proteins and Aspartate transaminase enzyme (AST) of the different phases for German cockroaches B. germanica , (p

Mutualistic stable symbioses are widespread in all groups of eukaryotes, especially in insects, where symbionts have played an essential role in their evolution. Many insects live in obligate relationship with different ecto- and endosymbiotic bacteria, which are needed to maintain their hosts’ fitness in their natural environment, to the point of even relying on them for survival. The case of cockroaches (Blattodea) is paradigmatic, as both symbiotic systems coexist in the same organism in two separated compartments: an intracellular endosymbiont (Blattabacterium) inside bacteriocytes located in the fat body, and a rich and complex microbiota in the hindgut. The German cockroach Blattella germanica is a good model for the study of symbiotic interactions, as it can be maintained in the laboratory in controlled populations, allowing the perturbations of the two symbiotic systems in order to study the communication and integration of the tripartite organization of the host–endosymbiont–microbiota, and to evaluate the role of symbiotic antimicrobial peptides (AMPs) in host control over their symbionts. The importance of cockroaches as reservoirs and transmission vectors of antibiotic resistance sequences, and their putative interest to search for AMPs to deal with the problem, is also discussed. more...

Cockroaches cause problems as pests not only locally in residential areas but also internationally, as they can disperse across borders in transport vessels. We investigated the effects of the ethyl formate (EF) fumigant on all developmental stages of Blattella germanica and Periplaneta americana. For B. germanica eggs, the hatching inhibition rate increased directly proportionately with the increasing treatment concentration of EF, but the 100% control was not observed. P. americana eggs did not show any fumigation effect, even after exposure to 60 mg/L of fumigant in a 12 L desiccator. Adults and nymphs of the two species showed various fumigation effects dependent on the concentration in the 12 L desiccator. When EF was applied at the lethal concentration for 99% mortality (LCT99) values of 35 mg/L for 4 h (78.5 mg·h/L) and 60 mg/L for 2 h (70.8 mg·h/L), respectively, adults and nymphs of both species had 100% mortality in a 0.65 m3 fumigation chamber with a 20% loading ratio. However, no significant difference from the control was observed in the egg stage of either species of cockroach. The results of this experiment indicate that EF can be used as a fumigant for cross-border transport vessels if the control period occurs during the cockroach developmental stage and continuous refumigation is performed. more...

Blattella germanica presents a very complex symbiotic system, involving the following two kinds of symbionts: the endosymbiont Blattabacterium and the gut microbiota. Although the role of the endosymbiont has been fully elucidated, the function of the gut microbiota remains unclear. The study of the gut microbiota will benefit from the availability of insects deprived of Blattabacterium. Our goal is to determine the effect of the removal (or, at least, the reduction) of the endosymbiont population on the cockroach’s fitness, in a normal gut microbiota community. For this purpose, we treated our cockroach population, over several generations, with rifampicin, an antibiotic that only affects the endosymbiont during its extracellular phase, and decreases its amount in the following generation. As rifampicin also affects gut bacteria that are sensitive to this antibiotic, the treatment was performed during the first 12 days of the adult stage, which is the period when the endosymbiont infects the oocytes and lacks bacteriocyte protection. We found that after this antibiotic treatment, the endosymbiont population remained extremely reduced and only the microbiota was able to recover, although it could not compensate for the endosymbiont role, and the host’s fitness was drastically affected. This accomplished reduction, however, is not homogenous and requires further study to develop stable quasi-aposymbiotic cockroaches. more...

German cockroach, Blattella germanica L., is one of the most health pests around the world. Development-temperature relationship and temperature-dependent parameters of B. germanica were determined in present study. The experiment was conducted in the incubators with five constant air temperatures, 23, 28, 31, 36, and 40 ℃. The photoperiod of 16 h light / 8 h dark and the relative humidity of 74%-76% were fixed for all incubators. Three replicates were set for each temperature. Based on linear regression equations, the estimated starting temperature for development of 1st to 5th instar nymphs of B. germanica is 14.26±3.157, 13.70±2.284, 14.59±3.575, 16.58±2.398, and 18.47±1.442 ℃, respectively. The estimated effective accumulated temperature of 1st to 5th instar nymphs is 99.18±19.68, 97.01±13.47, 92.06±21.17, 80.26±9.784, and 64.06±9.784 d ℃ (day degrees), respectively. B. germanica had the highest survivorship and hatching rate, and the least instars for eclosion and hatching time, around 31 ℃, which is the optimum temperature range for development and survival of B. germanica. B. germanica could not survive at 40 ℃. Even at 36 ℃, all eclosed adults had vestigial wings and could not normally mate and reproduce. more...

The entomopathogenic fungus Beauveria bassiana is the most important in biological control for many insects .In this study we used spores extract of entomopathogenic fungus to control German cockroach Blattella germanica with three concentrations (4.1x104 , 4.1x106 , 4.1x108 spore ml) and comparative with maxforce bait under laboratory condition (25 ± 2°C and 70 ± 10% RH). Both nymphs and adults are tested to detect the effect of pathogenic and bait . the results showed significant differences P more...

Symbiosis between prokaryotes and eukaryotes is a widespread phenomenon that has contributed to the evolution of eukaryotes. In cockroaches, two types of symbionts coexist: an endosymbiont in the fat body (Blattabacterium), and a rich gut microbiota. The transmission mode of Blattabacterium is vertical, while the gut microbiota of a new generation is mainly formed by bacterial species present in feces. We have carried out a metagenomic analysis of Blattella germanica populations, treated and non-treated with two antibiotics (vancomycin and ampicillin) over two generations to (1) determine the core of bacterial communities and potential functions of the gut microbiota and (2) to gain insights into the mechanisms of resistance and resilience of the gut microbiota. Our results indicate that the composition and functions of the bacteria were affected by treatment, more severely in the case of vancomycin. Further results demonstrated that in an untreated second-generation population that comes from antibiotic-treated first-generation, the microbiota is not yet stabilized at nymphal stages but can fully recover in adults when feces of a control population were added to the diet. This signifies the existence of a stable core in either composition and functions in lab-reared populations. The high microbiota diversity as well as the observed functional redundancy point toward the microbiota of cockroach hindguts as a robust ecosystem that can recover from perturbations, with recovery being faster when feces are added to the diet. more...

Insects are the only known animals in which sexual differentiation is controlled by sex-specific splicing. The doublesex transcription factor produces distinct male and female isoforms, which are both essential for sex-specific development. dsx splicing depends on transformer, which is also alternatively spliced such that functional Tra is only present in females. This pathway has evolved from an ancestral mechanism where dsx was independent of tra and expressed and required only in males. To reconstruct this transition, we examined three basal, hemimetabolous insect orders: Hemiptera, Phthiraptera, and Blattodea. We show that tra and dsx have distinct functions in these insects, reflecting different stages in the changeover from a transcription-based to a splicing-based mode of sexual differentiation. We propose that the canonical insect tra-dsx pathway evolved via merger between expanding dsx function (from males to both sexes) and narrowing tra function (from a general splicing factor to dedicated regulator of dsx). more...

Insects have close symbiotic relationships with several microbes, which extends the limited metabolic networks of most insects. Using symbiotic microorganisms for the biological control of pests and insect-borne diseases has become a promising direction. Blattella germanica (L.) (Blattaria: Blattidae) is a public health pest worldwide, which is difficult to control because of its strong reproductive ability, adaptability, and resistance to insecticides. In this paper, the diverse biological functions (nutrition, reproductive regulation, insecticide resistance, defense, and behavior) of symbionts were reviewed, and new biological control strategies on the basis of insect–symbiont interaction were proposed. We highlight new directions in B. germanica control, such as suppressing cockroach population using Wolbachia or paratransgenes, and combining fungal insecticides with synergistic agents to enhance insecticidal efficacy. more...

(1) Background: The widespread use of insecticides has cause extensive resistance in German cockroach (Blattella germanica) populations globally. Biological control has the potential to mitigate insecticide resistance, and Metarhizium anisopliae (Meschn.) Sorokin, an entomopathogenic fungus, alone and in combination with various insecticides, has shown good effects against cockroaches. (2) Methods: This experiment compared the cumulative mortality after infecting B. germanica with M. anisopliae conidia by two routes, per os and topical application. To probe the mechanisms that underlie the synergism between M. anisopliae and hydramethylnon, we conducted dose–response assays with cockroaches fed combinations of M. anisopliae and hydramethylnon and characterized the gut microbiomes of the treated cockroaches. (3) Results: The study showed that the mortality with per os infection was lower than that with topical application. In addition, the combination of M. anisopliae and hydramethylnon had a synergistic effect in 16 treatments. The gut microbiome was also altered by hydramethylnon treatment. The abundance of Parabacteroides and Enterococcus declined with the hydramethylnon and combination treatments, which are known to have anti-inflammatory and antifungal activities. The abundance of Alistipes, which is a fungal cell wall component, significantly increased in these treatments. (4) Conclusions: Therefore, we speculate that the major mechanism underlying this synergism is hydramethylnon promoting the survival of M. anisopliae in the harsh gut environment and enhancing its virulence for German cockroaches by altering the gut microbiome. This may provide a method for the fight against B. germanica and lay the foundation for the development of new baits. more...

Cockroaches have been associated with human environments threatening human health. A cross-sectional study about cockroach fungal contamination in the hospital, restaurant and household environments from Khorramabad, Lorestan province of Iran between August 2015 and March 2016 was done. Sampling was uniformly carried out monthly from the randomly selected sites. Fungi were isolated from the external surfaces of cockroaches using standard method. Periplaneta americana (66.7%) was found the most infested cockroach, less percentage were observed in Blattella germanica (18.6%) and Blatta orientalis (14.7%). Hospitals (66.7%) were found the most infested places in comparison with households (18.6%) and restaurants (14.7%). Households (64.3%) were found the most cockroach fungal contaminated places than hospitals (49.0%) and restaurants (59.1%). The highest and the lowest infestation of cockroaches were observed in January (30.0%) and March (7.0%) respectively, while the highest and the lowest cockroach fungal contamination were observed in November (73.3%) and March (14.3%). B. germanica (60.7%) was the most fungal contaminated cockroach. Candida, Geotrichum and Penicillium were the most frequent cockroach fungal contaminating genera. Statistical analysis revealed significant differences between cockroach infestation places (P=0.022), locality (P=0.03), and monthly (P=0.0001) cockroach fungal contamination, respectively. As a conclusion, the highest cockroach fungal contamination was observed in B. germanica, followed by P. americana and B. orientalis. Some human fungal opportunistic pathogens were also found among the fungal contaminated cockroaches. Recent epidemiological survey showed that the mortality rates of the infective diseases were increased, indicating cockroaches involved in their transferring. more...

No Abstract###

Background: The German cockroach, Blattella germanica L. (Dictyoptera: Blattellidae), has become resistant to many insecticides due to control failures in hospital and student dormitory settings of southern Iran. Objective: This study was thus designed to detect and monitor carbamate resistance in two strains of German cockroach using lethal dose bioassay methods. Methods: Wild dormitory (D) and hospital (H) strains were collected. Adult males were subjected to the jar exposure procedure. A range of concentrations based on the world health organization (WHO) standard concentration of carbamate insecticides (carbaryl, bendiocarb, propoxur) were used. For each insecticide, four to seven different concentrations leading to >0% and propoxur > bendiocarb. The ratio of LD50 in H strain to that of D strain for bendiocarb was about twice that of the other two insecticides indicating that German cockroaches were most susceptible to bendiocarb under both environments. Conclusion: It is concluded that excessive reliance on carbaryl in both D and H settings has led to resistance. more...

Certain monoterpenes produced by aromatic plants are known to have lethal and sublethal effects on insects. As there is a need to replace conventional pesticides (organophosphates, carbamates, pyrethroids) with biorational pesticides, we evaluated the behavioural and toxicological responses of the German cockroach, Blattella germanica, exposed to the following monoterpenes, namely (+)-a-pinene, (-)-a-pinene, limonene, menthone, linalool, menthyl acetate and geraniol. Locomotor activity and repellency were quantified using a video tracking system. To study the effect on locomotor activity, larvae were exposed to filter papers treated with concentrations of monoterpenes ranging between 1.4 and 1,400 µg/cm2. Only menthyl acetate applied at a concentration of 14 µg/cm2 or higher increased the locomotor activity of the larvae. Repellency was evaluated by exposing larvae to circles of filter paper divided in two equal zones: one zone was treated with a solution of a monoterpene in acetone (14 or 140 µg/cm2) and the other with only acetone. Larvae were repelled by all the monoterpenes tested. The two concentrations of geraniol and the highest concentration of menthyl acetate and linalool were as repellent as DEET (positive control). The fumigant effect was evaluated by exposing larvae to vapour from 100 µl of pure monoterpene in a sealed container. The values of the 50% Knock-down Times (KT50), expressed in minutes, were: (+)-a-pinene: 11.8, (-)-a-pinene: 14.6, limonene: 81.0, menthone: 141.0, and linalool: 238.6. (+)-a-Pinene was as good a fumigant as dichlorvos (positive control, KT50 = 9.7 min). The least effective compounds were menthyl acetate and geraniol (both affected less than 50% of larvae after 490 min of exposure). In conclusion, (+)-a-pinene (for its fumigant effect), menthyl acetate (for its hyperactivant effect) and menthone and geraniol (for their repellent properties) could potentially be used for controlling B. germanica. more...

Insects under different stimuli from the environment modify behavioural responses due to changes in the sensitivity of neurons at the peripheral and/or at the central level of the nervous system. This phenomenon is called neuronal plasticity, and sensory adaptation is an example of it. An insect repellent is a chemical that produces oriented movements of the insects away from its source. In this work we studied the modulation of the behavioural and electrical response to the repellent N, N-diethyl-3-methylbenzamide (DEET) in males of the German cockroach B. germanica produced by previous exposure to the same repellent. Methods. We determined repellency using a circular arena, one half of which was treated with DEET. The time spent by insects in each half of the arena was measured, and a repellency coefficient (RC) was calculated. The RCs of pre-exposed and non-pre-exposed insects were compared. To determine a possible role of nitric oxide in the modulation of the response to DEET after pre-exposure, the nitric oxide donor S-nitroso-acetyl-cysteine (SNAC) was applied on cockroaches’ antennae. The electrical activity of the cockroaches’ antennae in response to DEET was recorded using electroantennogram (EAG) technique. The response to DEET was recorded also after a long stimulation with the same repellent, and after topical application of SNAC and dbcGMP (a cGMP analogue) on the antennae. Results. We found that previous exposure of B. germanica males to the repellent DEET produced an increase of the repellency at the behavioural level, measured as RC. A possible role of nitric oxide (NO) in the transduction pathway of this phenomenon is suggested, since treatment of the cockroaches with the NO donor SNAC also produced an increase of the repellency elicited by DEET. On the other hand, the response of the cockroaches’ antennae exposed to DEET was determined electrophysiologically. The electrical activity in response to DEET decreased when the insects’ antennae were stimulated with a long pulse of the repellent. The activity of the antennae was restored after 10 min. Treatment of the antennae either with SNAC or dbGMPc also produced a decrease in the response of the antennae to the repellent. Discussion.The previous exposure to a chemical stimulus can modify the behaviour associated to the same stimulus, increasing or decreasing the behavioural response. In the case of DEET we found that pre-exposure increased DEET repellency in male cockroaches. We also found NO involvement in a similar phenomenon. On the other hand, the test showed that DEET is perceived by insects’ antennae as an odour. A long exposure of the antennae to DEET caused a transient decrease in the response of the antennae to the same compound. The same effect was achieved by treating the antennae with SNAC or dbcGMP, suggesting the involvement of the NO/cGMP system in the transduction pathway of the sensory adaptation phenomenon elicited by an odour in this species. more...

"nBackground: To compare the effectiveness of 3 commercial gel bait formulations containing fipronil (Goliathã Cockroach Gel 0.05% AI), chlorpyrifos-A (Clean Baitã Gel, 2% AI), and chloropyrifos-B (Serpaã Gel 2% AI) against German cock­roaches (Blattella germanica) when stored at 23°C and 30° C after treatment."nMethods: Laboratory bioassays consisted of placing groups of fifteen cockroaches (a random combination of adult, mixed sex and large nymphs-stage 6) into a 5 L cylindrical plastic container with one drop of product (avg 0.10 g ± 0.01 g) applied to a 76 mm x 26 mm glass microscope slide affixed to the bottom of each container (one product tested per container). Cumula­tive mortality was assessed at 6 h, 1, 2, 3, 4, and 5 d after application. To determine the further effects of storage tempera­ture after treatment on residual activity of the gels, a drop of each product was applied to separate glass microscope slides and stored at either 23º C (warm) or 30º C (hot) under dark conditions for 0, 1, 7, 14, 30, 45, 60 and 90 d after applica­tion."nResults: Freshly applied baits (day 0) containing fipronil provided complete cockroach mortality (100%) within 5 d whereas chloryrifos-A and chlorpyrifos-B provided »72% and 88% mortality, respectively. Generally, cockroach mortality was greater when gels were stored at 30°C compared with 23º C."nConclusion: The fipronil gel formulation proved to be as efficacious as the chlorpyrifos gels and in some instances sur­pased the latter formulations depending on storage time and temperature by providing »90% mortality at 90 d post treat­ment. more...

Background: The efficacy of essential oil of Chenopodium ambrosioides flowering aerial parts and its three main active ingredients was evaluated against Blattella germanica male adults. Methods: Composition of essential oil was determined by GC-MS. Topical application bioassay was used to evalu- ate contact toxicity of essential oil and three main components. Fumigant toxicity of essential oil and its main com- ponents was measured using a sealed space method. Results: Twenty-two components were identified in the essential oil and the main components were (Z)-ascaridole(29.7%), isoascaridole (13.0%), ρ-cymene (12.7%) and piperitone (5.0%). The essential oil and (Z)-ascaridole, isoascaridole and r-cymene possessed fumigant toxicity against male German cockroaches with LC50 values of 4.13,0.55, 2.07 and 6.92 mg/L air, respectively. Topical application bioassay showed that all the three compounds weretoxic to male German cockroaches and (Z)-ascaridole was the strongest with a LD50 value of 22.02 mg/adult while the crude oil with a LD50 value of 67.46 mg/adult. Conclusion: The essential oil from Chinese C. ambrosioides and its three main active ingredients may be explored as natural potential insecticides in the control of cockroaches. more...

Blattella germanica é uma barata domissanitária importante, desenvolvendo altas populações em restaurantes, residências, hospitais e locais de armazenamento de alimentos. Esse inseto tem sido presença constante em todos os cômodos dos apartamentos de um edifício residencial situado em uma cidade do interior paulista. Tendo em vista sua importância, como vetor de microrganismos potencialmente patogênicos, este trabalho propôs a avaliar seu potencial na transmissão de infecções, por meio do isolamento e identificação das bactérias encontradas em sua superfície. As amostras foram inoculadas em tubos com caldo TSB, que foram incubados a 37º C por 24 horas e depois plaqueados nos meios de ágar Müeller-Hinton, ágar Mac ConKey, e ágar manitol vermelho de fenol. Após incubação, os microrganismos isolados foram identificados por métodos convencionais. Em todas as amostras analisadas houve crescimento bacteriano. Em dez amostras foram isolados dois tipos de bactérias e em uma delas três tipos. Foram identificadas: Enterobacter sp (em onze amostras), Lactobacillus sp (em seis amostras), Bacillus cereus (em quatro amostras), Staphylococcus epidermidis (em quatro amostras), Escherichia coli (em duas amostras), Pantoea agglomerans (em duas amostras), Serratia sp (em uma amostra), Pseudomonas sp (em uma amostra), Bacillus subtilis (em uma amostra), Staphylococcus aureus (em uma amostra) e Enterococcus sp (em uma amostra). Considerando a presença de B. germanica nos apartamentos, transportando microrganismos associados a doenças de origem alimentar (E. coli, B. cereus e S. aureus), existe a possibilidade de contaminação de alimentos e transmissão dessas bactérias para humanos, portanto é importante orientar os moradores sobre as medidas para controle desses insetos. more...

Blattella germanica é uma barata domissanitária importante, desenvolvendo altas populações em restaurantes, residências, hospitais e locais de armazenamento de alimentos. Esse inseto tem sido presença constante em todos os cômodos dos apartamentos de um edifício residencial situado em uma cidade do interior paulista. Tendo em vista sua importância, como vetor de microrganismos potencialmente patogênicos, este trabalho propôs a avaliar seu potencial na transmissão de infecções, por meio do isolamento e identificação das bactérias encontradas em sua superfície. As amostras foram inoculadas em tubos com caldo TSB, que foram incubados a 37º C por 24 horas e depois plaqueados nos meios de ágar Müeller-Hinton, ágar Mac ConKey, e ágar manitol vermelho de fenol. Após incubação, os microrganismos isolados foram identificados por métodos convencionais. Em todas as amostras analisadas houve crescimento bacteriano. Em dez amostras foram isolados dois tipos de bactérias e em uma delas três tipos. Foram identificadas: Enterobacter sp (em onze amostras), Lactobacillus sp (em seis amostras), Bacillus cereus (em quatro amostras), Staphylococcus epidermidis (em quatro amostras), Escherichia coli (em duas amostras), Pantoea agglomerans (em duas amostras), Serratia sp (em uma amostra), Pseudomonas sp (em uma amostra), Bacillus subtilis (em uma amostra), Staphylococcus aureus (em uma amostra) e Enterococcus sp (em uma amostra). Considerando a presença de B. germanica nos apartamentos, transportando microrganismos associados a doenças de origem alimentar (E. coli, B. cereus e S. aureus), existe a possibilidade de contaminação de alimentos e transmissão dessas bactérias para humanos, portanto é importante orientar os moradores sobre as medidas para controle desses insetos. more...

Traps are tools frequently used to monitor and control pests. Therefore, it is important to study the prerequisites of their use. The instant active area of a trap (the instantly available area of a trap that is able to capture a pest) is a determinant of trap efficacy. However, to measure the instant active trap area is difficult. Therefore, we developed a technique of computer image analysis of digital photography to evaluate the instant active trap area, occupancy (area of insect bodies captured on the trap) and contamination (area of filth left by pests on the trap, such as wing-scales or faeces) of it. This study illustrates its use with two types of sticky traps applied to monitor the German cockroach, Blattella germanica, and the Mediterranean flour moth, Ephestia kuehniella. We found that moths decreased the capacity of the sticky surface more than cockroaches because of its contamination by wing-scales. The sticky trap area covered by wing-scales was nearly as large as the area occupied by moth bodies. Cockroaches contaminated the sticky surface by their faeces but the contaminated area was less than 2% of the area occupied by cockroach bodies. The results indicate that moths are heavy contaminators while cockroaches are weak contaminators of sticky traps. more...

Previous behavioural tests indicated that strain recognition and aggregation behaviour could be induced by cuticular hydrocarbons. The aim of this study was to document and to compare cuticular hydrocarbon profiles between different strains of Blattella germanica (L.) (Dictyoptera: Blattellidae) and to relate variations in the general profile of cuticular hydrocarbons with strain discrimination during behavioural tests. Profiles of different strains were remarkably similar qualitatively but presented slight quantitative differences over the 25 identified components. Important differences were observed in dimethylalkane components and these allowed separation of the strains into two groups using multivariate methods. Although we were not able to demonstrate a relationship between strain discrimination ability and differences in cuticular hydrocarbon profiles, we assumed that cuticular hydrocarbons could play two major roles in B. germanica strains. Less variable hydrocarbon profiles could play a role in species recognition and aggregation behaviour and the more variable part could play a role in strain discrimination. more...

This study was designed to evaluate the efficacy of beta-cyfluthrin (Responsar 12.5% SC), against a standard susceptible strain of German cockroach, Blattella germanica, using three different dosages, at three different exposure times, on two types of surface, parlous (mosaic) and non parous (glassed ceramic of tiles). Comparison of the resifts indicated that beta-cyfluthrin at 12.5 a.i.mg/m2, has negligent residual activity on both mosaic and glazed ceramic tiles from one to two weeks. However at 25 a.i.mg/m2 (highest dosage), had the longest residual activity on mosaic, it was active for six, seven and nine weeks, while on glazed ceramic tiles the residual activity increased slightly to seven and nine and nine weeks, when the nymphac were exposed for 10, 15 and 20 min, respectively. These results of the bio-assay test indicate that 12.5 a.i.mg/m2 is too low for any residual spraying. Application of beta-cyfluthrin at a target dosage rate of 25 and 37.5 a.i.mg/m2 showed longer residual deposit effect than the earlier dosage. Hence these dosages could be recommended for light and heavy infested area, respectively. This study is also recommends a simple device for measuring the residual activity of insecticides against German cockroach either in laboratory or in the field conditions. more...

Background: To compare the effectiveness of 3 commercial gel bait formulations containing fipronil (Goliathã Cockroach Gel 0.05% AI), chlorpyrifos-A (Clean Baitã Gel, 2% AI), and chloropyrifos-B (Serpaã Gel 2% AI) against German cock­roaches (Blattella germanica) when stored at 23°C and 30° C after treatment. Methods: Laboratory bioassays consisted of placing groups of fifteen cockroaches (a random combination of adult, mixed sex and large nymphs-stage 6) into a 5 L cylindrical plastic container with one drop of product (avg 0.10 g ± 0.01 g) applied to a 76 mm x 26 mm glass microscope slide affixed to the bottom of each container (one product tested per container). Cumula­tive mortality was assessed at 6 h, 1, 2, 3, 4, and 5 d after application. To determine the further effects of storage tempera­ture after treatment on residual activity of the gels, a drop of each product was applied to separate glass microscope slides and stored at either 23º C (warm) or 30º C (hot) under dark conditions for 0, 1, 7, 14, 30, 45, 60 and 90 d after applica­tion. Results: Freshly applied baits (day 0) containing fipronil provided complete cockroach mortality (100%) within 5 d whereas chloryrifos-A and chlorpyrifos-B provided »72% and 88% mortality, respectively. Generally, cockroach mortality was greater when gels were stored at 30°C compared with 23º C. Conclusion: The fipronil gel formulation proved to be as efficacious as the chlorpyrifos gels and in some instances sur­pased the latter formulations depending on storage time and temperature by providing »90% mortality at 90 d post treat­ment. more...

Background: Baits have become popular and effective formulations against urban insect pests. Compared with re­sidual sprays toxic gel baits are used more and more frequently to control urban cockroach populations. The aim of this study was to investigate the usage of two commercially available fipronil and imidacloprid gel bait formulations against Blattella germanica field infested in Iran. Methods: The study was carried out in an urban area at Tehran from March 2004 to September 2005. The 0.05% fipronil and 2.15% imidacloprid gel baits were placed continuously in 3 residential German cockroach infested units. Pre- and post-treatment cockroach density was assessed by visual count method. Results: Pre- and post-treatment visual count of cockroaches in treatment and control areas, and percentage reduc­tion in cockroach density in treatment areas in comparison to control areas was showed that density reduction was increased with the 0.05% fipronil and 2.15% imidacloprid gel baits in treated areas from 1st to 9th week in compari­son to control area. After 60 days, German cockroaches eliminated completely from these areas. Conclusion: These results show that fipronil and imidacloprid gel baits are highly effective in field German cock­roach infested after insecticide spraying control failure German cockroach infested fields where spraying of pyrethroid insecticides failed to control the situation and confirm previous reports stating that avermectin and hydramethylnon are more effective than conventional insecticides in baits against cockroaches. Therefore, fipronil and imidacloprid gel baits are appropriate candidates for controlling German cockroach infested dwellings in Iran where control with other insectices failed because of resistance. more...

This study was designed to evaluate the efficacy of beta-cyfluthrin (Responsar 12.5% SC), against a standard susceptible strain of German cockroach, Blattella germanica, using three different dosages, at three different exposure times, on two types of surface, parlous (mosaic) and non parous (glassed ceramic of tiles). Comparison of the resifts indicated that beta-cyfluthrin at 12.5 a.i.mg/m2, has negligent residual activity on both mosaic and glazed ceramic tiles from one to two weeks. However at 25 a.i.mg/m2 (highest dosage), had the longest residual activity on mosaic, it was active for six, seven and nine weeks, while on glazed ceramic tiles the residual activity increased slightly to seven and nine and nine weeks, when the nymphac were exposed for 10, 15 and 20 min, respectively. These results of the bio-assay test indicate that 12.5 a.i.mg/m2 is too low for any residual spraying. Application of beta-cyfluthrin at a target dosage rate of 25 and 37.5 a.i.mg/m2 showed longer residual deposit effect than the earlier dosage. Hence these dosages could be recommended for light and heavy infested area, respectively. This study is also recommends a simple device for measuring the residual activity of insecticides against German cockroach either in laboratory or in the field conditions. more...