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German cockroaches, Blattella germanica (L.), remain one of the most difficult indoor insect species to control because of its ability to develop resistance to insecticides. The toxicity and resistance levels of five technical-grade insecticides (permethrin, chlorpyrifos, propoxur, imidacloprid, and fipronil) were determined for adult males of seven strains of the German cockroach, a laboratory-reared susceptible strain (S) and six field-collected strains (B, D, E, G, H, and I). Using topical application methods, fipronil was the most toxic insecticide to all seven strains. The LD50 values of fipronil in the susceptible strain (S) and the field-collected strains B, D, E, G, H, and I were 1.33, 2.62, 11.53, 5.07, 7.66, 5.15, and 10.15 ng/insect, respectively. The field-collected strains were most resistant to permethrin among the five insecticides, except for strain H. The resistance ratios of strains B, D, E, G, and I to permethrin were 31.8, 37.3, 51.9, 34.9, and 37.5, respectively. With a resistance ratio of 6.4, the field-collected strain H was most resistant to chlorpyrifos. The field-collected strains were not significantly resistant to propoxur. Strains B, H, and I were not significantly resistant to imidacloprid when compared with the susceptible strain. Based on the different resistance ratios for each insecticide, we conclude that there are high rates of insecticide resistance in German cockroaches from Franklin County, NC, and that the field-collected strains most likely had different treatment histories.

The Asian cockroach, Blattella asahinai Mizukubo, is a peridomestic nuisance pest in the southeastern United States. Blattella asahinai is the closest relative to Blattella germanica (L.), the German cockroach, one of the most prolific and widespread domestic pests. Because these two species live in different habitats, they are expected to have differential development patterns reflecting environmental adaptations. Development of B. asahinai and B. germanica cockroach nymphs were observed at six constant temperatures ranging from 10 to 35 °C. At 10 °C and 15 °C, all nymphs died in the first instar, but B. germanica nymphs survived longer (10 °C: 12.9 d; 15 °C: 42.9 d) than B. asahinai nymphs (10 °C 8.2 d; 15 °C 18.4 d) at both temperatures. At 20 °C, 25 °C, and 30 °C, B. asahinai consistently had more instars and longer stadia than B. germanica. At 35 °C, only B. germanica was able to complete nymphal development; cannibalism among B. asahinai nymphs during molting was often observed at this temperature. The results for B. asahinai corroborated previously estimated growth patterns. The lower nymphal development threshold was 14.1 °C for B. germanica and 13.7 °C for B. asahinai. Comparing the development of B. germanica directly with its closest relative reveals specific physiological adaptations that B. germanica has developed for the indoor biome.

Cockroach management relies heavily on the use of conventional insecticides in urban settings, which no longer provide the anticipated level of control. Knowledge of cockroach endosymbionts, like Wolbachia, might provide novel avenues for control. Therefore, we screened 16 cockroach species belonging to 3 families (Ectobiidae, Blattidae, and Blaberidae) for the presence of Wolbachia. We mapped the evolution of Wolbachia-cockroach relationships based on maximum likelihood phylogeny and phylogenetic species clustering on a multi-loci sequence dataset (i.e., coxA, virD4, hcpA, and gatB) of Wolbachia genes. We confirmed the previous report of Wolbachia in 1 Ectobiid species; Supella longipalpa (Fab.), and detected the presence of Wolbachia in 2 Ectobiid species; Balta notulata (Stål) and Pseudomops septentrionalis Hebard, and 1 Blaberid species; Gromphadorhina portentosa (Schaum). All cockroach-associated Wolbachia herein detected were clustered with the ancestor of F clade Wolbachia of Cimex lectularius L. (bed bugs). Since Wolbachia provision C. lectularius with biotin vitamins that confer reproductive fitness, we screened the cockroach-associated Wolbachia for the presence of biotin genes. In toto, our results reveal 2 important findings: (i) Wolbachia is relatively uncommon among cockroach species infecting about 25% of species investigated, and (ii) cockroach-associated Wolbachia have biotin genes that likely provide nutritional benefits to their hosts. Thus, we discuss the potential of exploring Wolbachia as a tool for urban insect management.

German cockroaches, Blattella germanica (L.) (Blattodea: Ectobiidae), are important indoor insect pests and remain difficult to control because of their ability to develop resistance to insecticides. The toxicity, resistance levels, repellency, and performance index (PI) value of five formulated insecticides (permethrin, chlorpyrifos, propoxur, imidacloprid, and fipronil) were determined for adult males of seven strains of the German cockroach: a laboratory-reared susceptible strain (S) and six field-collected strains (B, D, E, G, H, and I). Propoxur was generally the most toxic insecticide to all strains using continuous exposure methods; however, using Ebeling choice box methods, chlorpyrifos, and fipronil were most toxic. In both continuous exposure and Ebeling choice box tests, the field-collected strains were generally most resistant to permethrin among the five insecticides. The greatest increase in resistance ratios between the two exposure methods was for permethrin and propoxur. Permethrin was the most repellent insecticide against all but two strains (D and H). PI values reached 100 (no repellency and complete mortality) for the susceptible strain against only chlorpyrifos and fipronil. Only fipronil resulted in a PI value of 100 for any of the field-collected strains. Continuous exposure and Ebeling choice box resistance ratios were correlated, and both were correlated with previously reported resistance ratios (based on LD50 values). Choice box repellency, however, was only correlated with LD50 resistance ratios. PIMax was negatively correlated with all measures of resistance ratios.

The German cockroach, Blattella germanica (L.) (Blattodea: Ectobiidae), is a ubiquitous pest in affordable housing. They represent a major threat to human health due to their contribution of asthma-exacerbating allergens and the potential to transfer pathogenic microorganisms indoors. Despite well-documented pyrethroid resistance, pyrethroid-based broadcast residual insecticide products are often used by residents to control cockroaches in their homes. Additionally, there is little empirical independent testing of these products. Thus, it remains unclear how effective these commonly used do-it-yourself products are at controlling German cockroaches. This study represents a comprehensive examination of the efficacy of these products with direct, limited, and continuous exposure assays on a variety of common household surfaces on field populations of cockroaches with varying levels of pyrethroid resistance. While most products performed well when applied directly to test insects, mortality was substantially lower across all surfaces with limited exposure (30 min). In continuous exposure assays on a nonporous surface, products took at least 24 hr to cause 100% mortality in a field population, with some products taking up to 5 d to achieve 100% mortality. The findings of this study demonstrate a lack of residual efficacy from common pyrethroid-based consumer-use pesticides products. Given that it is not feasible to find and treat every cockroach in a home directly, the residuality of spray-based formulations is critical for products designed to control German cockroaches. Without residual efficacy, as shown in the consumer aerosol and spray products tested, we expect these products to add little to no value to cockroach control.

Effective control of domestic and peridomestic cockroaches requires integrated approaches that emphasize concurrent use of chemicals with alternative control tactics. An integrated pest management (IPM) approach is particularly justified in environments where satisfactory cockroach control cannot be achieved due to multiple factors including development of insecticide aversion and resistance in some cockroach species, and poor sanitation or structural issues that foster infestations. While a flurry of research effort has been devoted to study alternative tactics for cockroach control, only a few of them have been evaluated in the context of IPM programs. This review focuses on examining studies on alternative tactics that are proven efficacious, economical, and logistically feasible for their inclusion in IPM programs for important domestic and peridomestic cockroaches in the USA. Management programs that educate the public on cockroach biology, behavior, and the importance of sanitation; use of traps to monitor infestation levels; apply targeted low impact insecticides such as baits, have demonstrated a greater success for effective and sustainable control of cockroaches when compared to an insecticide-only approach. Incorporation of other alternative control methods to IPM programs will require more applied research that validates their use in real-world scenarios and demonstrates their cost-effectiveness.

Aprostocetus hagenowii (Ratzeburg) is a parasitoid wasp that parasitizes the oothecae of peridomestic pest cockroaches. A. hagenowii has been used in integrated pest management (IPM) programs for cockroach control but little is known about how this parasitoid responds to the insecticides commonly used for cockroach management. Five insecticidal gel bait products containing indoxacarb, clothianidin, fipronil, dinotefuran, or abamectin B1 were tested for their toxicity towards A. hagenowii and the American cockroach, Periplaneta americana (L.; Blattodea: Blattidae), a host of A. hagenowii and a common pest. All baits were tested as fresh and 1-d aged deposits. Indoxacarb was the only active ingredient that did not cause significant (P < 0.05) A. hagenowii mortality compared to the control in both the fresh and aged gel experiments (Median survival time [MST]s: 168 h fresh, 72 h aged). Clothianidin caused the lowest A. hagenowii MSTs across experiments (24 h, fresh and aged). All baits caused significant P. americana mortality as fresh and 1-d aged deposits (P < 0.05). Indoxacarb appears most compatible with A. hagenowii in cockroach IPM.

Telomeres consist of highly conserved simple tandem telomeric repeat motif (TRM): (TTAGG)n in arthropods, (TTAGGG)n in vertebrates, and (TTTAGGG)n in most plants. TRM can be detected from chromosome-level assembly, which typically requires long-read sequencing data. To take advantage of short-read data, we developed an ultra-fast Telomeric Repeats Identification Pipeline and evaluated its performance on 91 species. With proven accuracy, we applied Telomeric Repeats Identification Pipeline in 129 insect species, using 7 Tbp of short-read sequences. We confirmed (TTAGG)n as the TRM in 19 orders, suggesting it is the ancestral form in insects. Systematic profiling in Hymenopterans revealed a diverse range of TRMs, including the canonical 5-bp TTAGG (bees, ants, and basal sawflies), three independent losses of tandem repeat form TRM (Ichneumonoids, hunting wasps, and gall-forming wasps), and most interestingly, a common 8-bp (TTATTGGG)n in Chalcid wasps with two 9-bp variants in the miniature wasp (TTACTTGGG) and fig wasps (TTATTGGGG). Our results identified extraordinary evolutionary fluidity of Hymenopteran TRMs, and rapid evolution of TRM and repeat abundance at all evolutionary scales, providing novel insights into telomere evolution.

The Turkestan cockroach, Blatta lateralis (Walker), is a peridomestic pest of growing concern in the US Southwest. The parasitoid Aprostocetus hagenowii (Ratzburg) is used in IPM programs targeting other blattid cockroach species and may aid in B. lateralis suppression. Information about the ability of A. hagenowii to parasitize B. lateralis is lacking. A no-choice host-switching experiment was used to test A. hagenowii acceptance of B. lateralis oothecae, and a multigenerational no-choice experiment was used to determine the suitability of B. lateralis as a host for A. hagenowii over several months of rearing. Periplaneta americana (L.) (Blattodea: Blattidae), the preferred host of A. hagenowii, and Blatta orientalis L., a known host and relative of B. lateralis, were used for comparison. Development time was similar among hosts and generations (P > 0.05). Parasitism success and proportion of female progeny declined significantly with subsequent generations on both Blatta spp. (parasitism success: χ2 = 14.916; df = 2; P = 0.001; proportion female: H = 6.364; df = 2; P = 0.041). These results suggest that A. hagenowii may initially aid in suppression of B. lateralis, but an overall decline in fitness will require repeated releases or provisioning of P. americana oothecae. Development of a strain more suitable for B. lateralis control may be possible via selection from laboratory strains or through use of wild A. hagenowii from areas where B. lateralis is present.

Abstract Aprostocetus hagenowii (Ratzburg) is a generalist parasitoid of cockroach (Blattodea) oothecae. Previous studies examining the host range of A. hagenowii have largely focused on cockroaches of economic and medical importance, which represent a minority of species in an order filled with species of diverse morphology, behavior, and ecology. The aim of this study was to expand the known host range of A. hagenowii with emphasis on nonpest as well as pest species from 3 cockroach families (Blattidae, Corydiidae, and Ectobiidae). Previously recorded host species were also reexamined. Oothecae from 17 cockroach species were exposed to A. hagenowii. Three new host species were recorded: Blatta lateralis (Walker) (Blattidae), Neostylopyga propinqua (Shelford) (Blattidae), and Parcoblatta fulvescens (Saussure and Zehntner) (Ectobiidae). Among the reexamined host species Periplaneta australasiae (Fab.) (Blattidae), Blatta orientalis L. (Blattidae), and Neostylopyga rhombifolia (Stoll) (Blattidae) were successfully parasitized. The cuticle thicknesses of 7 cockroach species’ oothecae were also investigated. There were significant differences [Kruskal–Wallis: each zone (below keel, side, and bottom) measured P < 0.001] in cuticle thickness among the species measured. Polyphaga sassurei (Dohrn) (Corydiidae) and Eurycotis floridana (Walker) (Blattidae) had the thickest cuticles (each zone >0.09 mm) and Blattella germanica (L.) (Ectobiidae) had the thinnest (each zone <0.03 mm). However, the mean A. hagenowii ovipositor length (0.92 mm ± 0.01 mm) far exceeded the thickest oothecae measured. Oothecal cuticle thickness alone was not observed to determine the host suitability of each tested cockroach species for A. hagenowii.