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PubMed1990

Sublethal effects of chlorpyrifos-methyl on reproduction in female German cockroaches (Dictyoptera: Blattellidae).

Longevity and lifetime fecundity were significantly reduced after topical application of LC10, LC20, and LC60's of chlorpyrifos-methyl to 2-d-old female German cockroaches, Blattella germanica (L.). Low concentrations (LC10 and LC20) often resulted in failure of the first ootheca to hatch. This effect is temporary, and greater than or equal to 90% of subsequent oothecae hatched normally. Application of an LC60 also resulted in a high percentage of abortions of first oothecae, but also caused greater than 15% inviability in subsequent oothecae.

Animals↗
PubMed1990

Morphogenetic effects of hydroprene on genitalia of the oriental cockroach (Dictyoptera: Blattidae).

Hydroprene had a considerable effect on the morphogenesis of external genitalia of the oriental cockroach, Blatta orientalis L. Exposure of nymphs to hydroprene resulted in abnormal adultoids with structural and positional distortions, and reduced or absent cuticular sclerotizations of the external genitalia. Late nymphal instars were significantly more sensitive to hydroprene than were early instars. In males, the epithelial cells of wings, serrata of the right phallomere, titillator and other lobes of the left phallomere were sensitive to hydroprene. The left phallomere was often prolapsed, distorted, and reduced in sclerotization. The right phallomere, particularly the serrata, was extremely malformed. In severe cases, phallomeres were entirely distorted or fused to each other. In females, the overall structure of the ovipositor appeared flaccid, less sclerotized, and misshapen. The first and second pairs of valvulae were often misshapen and reduced in sclerotization and length, or even fused with the third valvulae. This study provides morphological evidence that B. orientalis with malformed genitalia after treatment with hydroprene would be unsuccessful in copulation and fertilization. A high correlation between wrinkled wings and malformed male genitalia can be an important criterion to evaluate the effects of hydroprene on this species.

Animals↗
PubMed1990

Residual effectiveness of insecticides for control of German cockroaches (Dictyoptera: Blattellidae) in food-handling establishments.

Residual effectiveness of insecticides was compared for two treatment methods at various sites within two commercial kitchens. For all sites and insecticides, German cockroach, Blattella germanica (L.), mortality was greatest for treatments of cracks and crevices than for treatments of exposed surfaces. Mortality at the dishwashing site was lower than at all other sites. We attributed reduced mortality at the dishwashing site to a higher vapor pressure deficit. Mortality and the amount of insecticide residue recovered from treated surfaces were closely correlated. These data demonstrate that careful placement of residual insecticide treatments will influence their effective longevity.

Animals↗
PubMed1991

Extended selections for pyrethroid resistance in the German cockroach (Dictyoptera: Blattellidae).

Selection experiments with a pyrethrins-susceptible and a pyrethrins-resistant strain of German cockroaches, Blattella germanica (L.), were conducted for 17 generations with either permethrin or fenvalerate as the selecting agent. Large nymphs were left on treated glass surfaces for extended periods of time each generation. Mortality was assessed at 24 h. The level of resistance was determined periodically by time-mortality testing. The VPI-susceptible strain served as the basis for comparison. The pyrethrins-susceptible strain developed resistance to pyrethrins early in the selection process; this strain ultimately became resistant to allethrin, phenothrin, permethrin, fenvalerate, cyfluthrin, and cypermethrin. Fenvalerate caused faster development of resistance than did permethrin. The pyrethrins-resistant strain, selected with fenvalerate, quickly became resistant to allethrin, permethrin, phenothrin, and fenvalerate. Ultimately, it developed resistance to all nine pyrethroids tested.

Animals↗
PubMed1991

Effect of temperature on the toxicities of ten pyrethroids to German cockroach (Dictyoptera: Blattellidae).

Of 10 pyrethroids tested by topical application of male German cockroaches, Blattella germanica (L.), d-phenothrin was the least toxic at 19, 26, or 31 degrees C. lambda-cyhalothrin was most toxic. Pyrethroids with the alpha-cyano moiety (fluvalinate, fenvalerate, cypermethrin, esfenvalerate, tralomethrin, cyfluthrin, and lambda-cyhalothrin) were more toxic than those without this functional group (d-phenothrin, resmethrin, and permethrin). At LC50, toxicity was negatively related to temperature. Temperature-toxicity responses of five of seven alpha-cyano pyrethroids were parallel, possibly indicating qualitatively identical but quantitatively different levels of detoxification enzymes.

Animals↗
PubMed1992

Differences in the response of German cockroach (Dictyoptera: Blattellidae) field strains to vapors of pyrethroid formulations.

Late-instar German cockroaches from an insecticide-susceptible field strain (Fairbanks) and four pyrethroid-resistant field strains were exposed to vapors of a cyfluthrin flowable concentrate (FC) and the formulation blank (formulation without the active ingredient). Experiments with other pyrethroid formulations were done with the Fairbanks strain and an insecticide-resistant field strain (K-851) because these strains exemplified the maximum interstrain variation in experiments with the FC. In these experiments, I used a cyfluthrin wettable powder (WP) and its blank, a cyfluthrin emulsifiable concentrate (EC), and a permethrin aerosol and its blank. Vapors of the FC and its blank caused the most rapid dispersal. Dispersal induced by vapors of the WP, EC, and aerosol formulations was low and variable. In general, less of a dispersal response occurred in the resistant strains than in the susceptible strain. The strain mostly highly resistant to pyrethroids (K-851) dispersed slowly compared with the other resistant strains in experiments with the FC and its blank. When vapor-induced dispersal was relatively low (less than 50%), a trend was still evident towards less dispersal in the K-851 strain than in the Fairbanks strain. Although dispersal in experiments with the FC did not differ significantly from that in experiments with the FC formulation blank, mean percentage dispersal at the end of the experiments was higher with the formulation blanks than with the complete formulations in experiments with the WP and permethrin aerosol.

Animals↗
PubMed1992

Differential development and reproduction of the German cockroach (Dictyoptera: Blattellidae) on three laboratory diets.

Development of nymphs and oocyte maturation in adults were examined in Blattella germanica (L.) reared on three commercial diets. Nymphs fed rat food developed significantly faster than nymphs fed two commercial dog foods. Similarly, oocytes matured more quickly in adult females that were raised on rat food than in females raised on dog food. Nymphal development and oocyte maturation were slower in insects that were fed whole dog food pellets than in insects fed ground dog food, suggesting that grinding the diet diminishes a mechanical barrier in whole dog food pellets. Comparisons of processed canine food and unprocessed canine food indicated that diets were significantly inferior after the steam extrusion process. Rat food is normally not subjected to such conditions and both processed and unprocessed rat food are equally suitable for B. germanica. The significance and implications for comparative studies with cockroaches are discussed.

Animal Feed↗
PubMed1992

Oral toxicity, formulation effects, and field performance of flufenoxuron against the German cockroach (Dictyoptera: Blattellidae).

Laboratory and field studies on the benzoylphenyl urea (BPU) chitin synthetase inhibitor flufenoxuron (DPX EY-059) showed great potential for its use in suppressing infestations of German cockroach, Blattella germanica (L.). When fed continuously to fifth (last) instars, the LC50 of flufenoxuron was estimated at 0.82 ppm (95% FL, 0.76-0.87 ppm). A rating scale specific for BPU effects was developed and shown to be positively correlated with the insect's exposure to concentration of flufenoxuron. Manipulating the particle size of wettable powder formulations of flufenoxuron significantly altered their activity in contact bioassays. Larger particles (volume mean diameter, 12.2 mu; range, 10-20 mu) were more active. Field trials in multifamily housing with this wettable powder formulation at 0.033 and 0.066% (AI) achieved high level (greater than 80%) population suppression within 8 wk of treatment. The potential for the use of flufenoxuron in B. germanica management programs is discussed.

Animals↗
PubMed1992

Sublethal effects of insecticides on adult longevity and fecundity of German cockroaches (Dictyoptera: Blattellidae).

The effects of sublethal concentrations of chlorpyrifos, cyfluthrin, and hydramethylnon on adult longevity and fecundity of German cockroaches, Blattella germanica (L.), were investigated. Longevity of males declined linearly with increasing doses of insecticide. An LD50 of cyfluthrin decreased male longevity by 52%, whereas an LD50 of hydramethylnon reduced male longevity by 81%. Longevity of females increased linearly with increasing sublethal doses of chlorpyrifos, whereas all doses of both cyfluthrin and hydramethylnon decreased longevity of females. Fecundity increased linearly with increasing sublethal doses of chlorpyrifos. Number of oothecae formed, oothecae hatched, and number of offspring produced in each ootheca increased with increasing sublethal concentrations of chlorpyrifos. In contrast, fecundity declined with increasing sublethal concentrations of cyfluthrin and hydramethylnon. Formation of the first ootheca occurred approximately 8 d after mating for untreated females but generally longer with sublethal concentrations of all insecticides. The period between oothecae hatch and the formation of subsequent oothecae increased with successive oothecae in all treatments.

Animals↗
PubMed1993

Activity and electrophoretic characterization of esterases in insecticide-resistant and susceptible strains of German cockroach (Dictyoptera: Blattellidae).

Strains of German cockroach, Blattella germanica (L.) were tested for resistance to three insecticides using the time-mortality response technique in comparison with known susceptible strains. Dursban-R and Macy strains indicated high levels of resistance to chlorpyrifos and moderate resistance to propoxur and cypermethrin. The hydrolytic activity of esterase enzymes was determined with a model substrate, p-nitrophenyl acetate. The specific activity of the enzymes increased with a corresponding increase in substrate concentration. Maximum activity was observed at 80 microM. The resistant strains had significantly higher activity than the susceptible strains. The enzyme activity also increased with an increase in pH. Highest esterase activity was observed at pH 8.0 for all the strains. The calculated Michaelis Menten constant (Km) values for the resistant strains were nearly two-fold higher than for the susceptible strains. Nondenaturing gel electrophoresis revealed differences in isozyme composition. In total, 10 esterase bands were detected, and these bands were characterized using different inhibitors and substrates.

Animals↗
PubMed1993

Possible mechanisms of organophosphorus and carbamate insecticide resistance in German cockroaches (Dictyoptera: Blattelidae) from different geographical areas.

The resistance status of 14 strains of Blattella germanica (L.) from four countries was determined for chlorpyrifos and propoxur compared with a standard reference susceptible strain. Thirteen strains were resistant to chlorpyrifos; 12 strains were resistant to propoxur. Resistance ratios for chlorpyrifos ranged from 8- to 462-fold at LC90; for propoxur, resistance ratios ranged from 4- to 46-fold. One cockroach strain from Denmark had negative cross-resistance to chlorpyrifos, and one strain from the United States had negative cross-resistance to propoxur. Slopes of probit regressions indicated that all resistant strains were heterogeneous for resistance to both chlorpyrifos and propoxur. Synergist studies with piperonyl butoxide indicated that multifunction mono-oxidases are probably involved in resistance to chlorpyrifos in six strains and in resistance to propoxur in seven strains. Esterase activity was elevated in 10 strains; of these strains, two had only slightly elevated esterase activity as measured with the substrates 1- and 2-naphthyl acetate. The remainder had higher levels of elevated esterase activity to both substrates. Strains with elevated esterase activity were resistant to a broad spectrum of organophosphates, pyrethroids, or both. Increased levels of glutathione S-transferase activity were found in four strains. Another two strains had a low frequency (1%) of individuals with high glutathione S-transferase activity. Elevated glutathione S-transferase activity was not correlated with the observed levels of organophosphate or carbamate resistance. One strain from Dubai had an altered acetylcholinesterase-based mechanism that conferred broad-spectrum resistance to a range of organophosphates and carbamates.

Animals↗
PubMed1993

Decline of pyrethroid resistance in the absence of selection pressure in a population of German cockroaches (Dictyoptera: Blattellidae).

The level of resistance to seven pyrethroids was followed in a laboratory-selected population of Blattella germanica (L.) for 15 generations, during which time it was not exposed to any insecticide. As estimated by LT50 resistance ratios (RRs), resistance declined in a stepwise manner to preselection levels with all of the pyrethroids except pyrethrins. I also compared the levels of resistance as indicated by RRs and by gene frequency (GF) estimates. Results showed that GF estimates provide a more precise indication of the changes in resistance that occur over time than do RRs alone, especially when combined with RR and end-point mortality data. I discuss my results from the standpoints of the number of genetic mechanisms involved in pyrethroid resistance in this insect, and what the declines in resistance mean for future cockroach control.

Animals↗
PubMed1994

Subcellular distribution and characterization of esterase isozymes from insecticide-resistant and -susceptible strains of German cockroach (Dictyoptera: Blattellidae).

Esterases from insecticide-resistant and -susceptible strains of German cockroach, Blattella germanica (L.), were isolated and analyzed for differences in activity. The isozymes E5, E6, E7, and E8 of resistant strains indicated about two- to fivefold increases in activity compared with those of the susceptible strain. These isozymes constituted approximately 60% of the total activity in the resistant strains, whereas they contributed only about 40% activity in the susceptible strain. Subcellular distribution studies showed that most esterase activity is present in the 100,000 x g fraction of the homogenate (cytosolic). Only a small portion of activity was membrane bound. Molecular weights of the esterase isozymes calculated based on their retardation coefficients ranged between 48 and 81 kd.

Animals↗
PubMed1994

Effects of three synergists on pyrethroid resistance in the German cockroach (Dictyoptera: Blattellidae).

The effects of three synergists on the level of resistance to eight pyrethroids were examined in field-collected populations of the German cockroach, Blattella germanica (L.). Resistance to allethrin was not affected by piperonyl butoxide (PBO), (2-(2-ethylhexyl)-3a,4,7,7a-tetrahydro-4,7-methano-1H-isoindole-1,3(2H)- dione (MGK 264), or S,S,S-tributyl phosphorotrithioate (DEF). Resistance to pyrethrins also was not affected by these synergists in the same or similar strains but was negated almost completely by them in strains resistant only to pyrethrins. Resistance to permethrin, cypermethrin, and cyfluthrin largely was negated by these synergists. Results were variable with esfenvalerate, fenvalerate, and especially phenothrin. For example, with phenothrin the synergists were partially effective against some strains but were totally ineffective against others. The results appear to be unrelated to the chemistry of the pyrethroids studied. I report evidence that indicates the possible presence of several independent resistance mechanisms. My results suggest that these synergists generally will not combat pyrethroid resistance in this species, although they are highly effective in some cases.

Animals↗
PubMed1994

Abamectin resistance potential in the German cockroach (Dictyoptera: Blattellidae).

Twelve field-collected populations of German cockroaches, Blattella germanica (L.), were examined for resistance to dietary abamectin at 40 ppm. Half of these populations had significantly increased resistance ratios compared with the VPI-susceptible strain, but the highest value was only 2.4. Feeding inhibition was variable but nevertheless pronounced in all 12 strains. Feeding-choice tests with two strains revealed that each strain consumed treated and untreated food about equally. Mortality was reduced in both strains. Cross-resistance from cyclodiene resistance was not found. Low-level selections with abamectin did not result in increased resistance. Whereas resistance to abamectin does not appear to be a problem at present, two potential resistance mechanisms were identified and are discussed briefly.

Animals↗
PubMed1994

Diel activity cycles in nymphal stadia of the German cockroach (Dictyoptera: Blattellidae).

Computerized moving-image analysis was used to determine movement behavior of individual German cockroach, Blattella germanica (L.), nymphs (second and fifth instars) between food, water, and harborage resource sites. Both second and fifth instars (n = 10) were examined for the entire nymphal stadium, during which a 12:12 (L:D) photoperiod was maintained. In addition, corresponding resource consumption rates for these nymphal stages also were determined. Both nymphal stages exhibited a pattern of high activity for the first half of the nymphal stadium, especially during each scotophase. For the last third of the stadium, the nymphs remained continuously in the harborage, moved very little, and consumed little or no resources. We discuss implications of these findings regarding control, future research, and possible hormonal behavior regulation.

Animals↗
PubMed1994

Hydroprene effects on the dynamics of laboratory populations of the German cockroach (Dictyoptera: Blattellidae).

The influence of sterilization by hydroprene on population dynamics in the German cockroach, Blattella germanica (L.), was studied in the laboratory where more detailed and accurate assessments could be achieved than would be possible under typical field situations. The gradual accumulation of sterile adultoids (i.e., adults with twisted wings, indicating exposure to hydroprene) during treatment, or their decreasing abundance after treatment, produced distinctive patterns in the dynamics of treated populations. The percentage of gravid females (a reproductive index) was first to respond to treatments, because increases (or decreases) in the percentage of gravid females preceded reductions (or recoveries) in sample density and nymph-to-adult ratios by 4-6 wk. Trends in the percentage of adultoids were negatively correlated with the percentage of gravid females and indirectly measure the activity of hydroprene. Initial reductions in the percentage of gravid females, sample density, and nymph-to-adult ratios began at or about the time when approximately 80% of adults had twisted wings (i.e., were adultoids). As the percentage of adultoids attained (or declined below) the 80% level, we can accurately predict the subsequent decline (or recovery) in nymph-to-adult ratios and, thus, sample density. These data support a proposal to adopt the 80% level of adultoids as an action threshold for regulating juvenoid treatments to maximize population suppression. The role of this action threshold in the long-term management of chronic B. germanica infestations or insecticide resistant populations is discussed.

Animals↗
PubMed2005

Population genetics of wood-feeding cockroaches in the genus Cryptocercus.

Members of the genus Cryptocercus are xylophagous, wingless, subsocial cockroaches that inhabit decaying logs in temperate forests. Given their winglessness, subsocial living, and the patchy distribution of food resources (decomposing logs), it is likely that Cryptocercus populations are substructured. Allozyme variation at eight polymorphic loci was assayed for 10 subpopulations of Cryptocercus darwini and 13 subpopulations of Cryptocercus wrighti, both of which are distributed in the Appalachian Mountains. The mean F(IS) was 0.13 and F(ST) was about 0.25 for both C. darwini and C. wrighti. The relatedness among individuals of a subpopulation of both species was not significantly different from that expected among full sibs. In terms of how genetic variation is partitioned, C. darwini and C. wrighti differed from each other substantially. Most of the genetic variation occurred among subpopulations of C. wrighti in the same region and among subpopulations of C. darwini in different regions. We discuss the factors that may have contributed to the observed similarities and differences in the breeding structure of the two species.

Animals↗