RESUMEN

Lactones are cyclic esters of hydroxy carboxylic acids, present in several fruits and animals consumed by humans. There is evidence that some lactones modify insect behavior. The aim of the present study was to evaluate the repellent effect of four lactones (γ- and δ-nonalactone, and γ- and δ-dodecalactone) in first instar nymphs of the German cockroach, Blattella germanica (Linnaeus). To assess repellency, a nymph was placed on a circle of filter paper, half of which had been treated with lactone dissolved in acetone and the other half with acetone alone. The behavior of the nymph was recorded and the time the nymph spent in each half of the paper was quantified using Ethovision XT 10.1 software. Values of Distribution Coefficient (DC) were calculated: DC = (Tt - TA) / Tt, where Tt is the experimental time and TA is the time the nymph spent in the area treated with the repellent agent. DC can vary between 0 and 1. Values significantly higher than 0.5 indicate repellency. N,N-diethyl-meta-toluamide (DEET) was used as a positive control. DEET, δ- and γ-nonalactone caused repellency as from 77.9 µg/cm2, whereas γ- and δ-dodecalactone had a repellent effect starting at 779.0 µg/cm2. The values of DC for these concentrations were 0.89 (DEET), 0.86 (γ-nonalactone), 0.87 (δ-nonalactone), 0.83 (γ-dodecalactone), and 0.72 (δ-dodecalactone). To our knowledge, this is the first report of repellency produced by lactones in the German cockroach. This work allowed to identify two lactones that have a repellent effect similar to DEET.

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In this work, it was studied the role of faeces in the location and permanence in a shelter in susceptible and pyrethroid-resistant individuals of Blattella germanica (Linnaeus 1767). Additionally, the effect of different concentrations of palmitic acid on the modulation of these behaviours was tested. A shelter constituted by a square cardboard structure was offered to susceptible as well as to resistant specimens. The shelter bases were treated with faecal extracts obtained from susceptible or resistant cockroaches, or with solutions of palmitic acid. The behaviour of susceptible as well as resistant specimens was analysed using infrared videography software. Susceptible's faecal extract attracted both specimens since the time spent by cockroaches to locate the treated shelters was lower, whereas the faecal extract from resistant insects did not elicit any effect on both strains. Faecal extracts showed an arrestant effect on both strains, suggested by the time spent inside the shelter that was significantly higher in their presence. On the other hand, treatment with palmitic acid produced an attractant or a repellent effect depending on the concentration and strain. The tested lower concentration was attractant to susceptible insects, but did not produce any effect on resistant ones. In addition, the higher concentrations did not produce any effect on susceptible individuals, but resulted repellent for resistant ones. Palmitic acid did not produce an arrestant effect on the strains as there was not an increase in time spent inside the shelter in the presence of this substance. An increase in the number of visits to the shelter and to the periphery was also observed in shelters treated with the faecal extract and with the lower concentration of palmitic acid. These results show that compounds of the susceptible faeces were attractant to cockroaches of both strains, while faecal extracts from resistant insects were not. Moreover, a dual effect of palmitic acid was observed, being attractant at low concentrations and repellent as concentration increased. Additionally, a difference in the concentration threshold at which the effect of this substance changes was observed between strains.

RESUMEN

Blattella germanica (Linneaus, 1767) es una especie de cucaracha considerada plaga de la salud pública por estar asociada a gran número de microorganismos causantes de enfermedades al hombre. Para su control se utilizan diferentes tipos de formulaciones a base de insecticidas sintéticos a los cuales en su gran mayoría es resistente. En este contexto existe un interés creciente por los insecticidas botánicos. En el siguiente trabajo se evaluaron los aceites de Citrus aurantium (L.,1753), Ocimum basilicum (L.,1753), Piper aduncum subsp ossanum (C.DC. Saralegui) y Eucalyptus globulus (Labill, 1800) mediante aplicación tópica de un microlitro en el primer esternito abdominal de los individuos. Los cuatro aceites mostraron actividad insecticida sobre adultos de B. germanica con CL50 que oscilaron entre 58 µg/µL para O. basilicum y 250 µg/µL para P. aduncum(AU)´

Blattella germanica (Linneaus, 1767) is a cockroach species considered a public health pest, since it is associated with a great number of disease-causing microorganisms in humans. For its control, different types of synthetic-based insecticidal formulations are used, to which it is mostly resistant. In this context, there is a growing interest in botanical insecticides. In this research, oils from Citrus aurantium (L., 1753), Ocimum basilicum (L., 1753), Piper aduncum subsp. ossanum (C.DC. Saralegui), and Eucalyptus globulus (Labill, 1800) were evaluated by topical application of 1 µL to the first abdominal sternum of the individuals. The four essential oils evaluated showed insecticidal activity against adult B. germanica with LC50 ranging from 58µg/µL for O. basilicum to 250µg/µL for P. aduncum(AU)´

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The use of chemical insecticides is the main control method for Blattella germanica worldwide. The prolonged and frequent use of insecticides produced the selection of insecticide-resistant individuals. The German cockroach is one of the most widespread urban pests in Argentina. In the last decades, resistance monitoring studies in this country demonstrated that there is a high prevalence of pyrethroid-resistant populations of B. germanica in the field. In this work, we studied the resistance mechanisms of a field-collected strain of B. germanica at toxicological, enzymatic, and molecular levels. A resistance ratio of 100 was obtained for the resistant strain when it was exposed to ß-cypermethrin. The pretreatment with specific synergists (piperonyl butoxide and triphenyl phosphate) led to a significant increase in the toxicity of the pyrethroid, suggesting an involvement of oxidases and esterases in the detoxification of this insecticide. Moreover, esterase and oxidase activities in the resistant strain were 1.5-fold and 2-fold higher respectively, compared to the susceptible individuals. On the other hand, the voltage-gated sodium channel gene of the resistant cockroaches did not show nucleotidic substitutions in the domain II which are associated to knockdown resistance in this species. These results suggest that the main mechanism of resistance of the studied cockroaches' strain is metabolic, mainly due to an increase in the activity of oxidase and esterase enzymes. The results of this work in addition to other reports found in literature show that the extended use of a single active principle for cockroach control promotes the development of resistance leading to control failure in the field. In contrast, integrated pest management strategies include the use of different control tools in addition to chemical insecticides, which delay the appearance of resistance increasing the efficacy of pest control.

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The German cockroach, Blattella germanica L., is a hemimetabolous insect pest of economical and medical importance. N,N-diethyl-3-methylbenzamide (DEET) is an insect repellent whose effect on this species has received very little attention. The objective of this work was to determine whether the behavioral response of B. germanica to DEET varies along its life cycle. DEET repellence was assessed in small, medium, and large nymphs, and in adults of both sexes, all originated from the same laboratory colony (CIPEIN). The experimental arena consisted in a piece of filter paper treated with repellent on one half (195 µg/cm2) and solvent alone on the other half. A cockroach was placed on the filter paper, and its behavior was filmed. An image analyzer was used to quantify how long the insect spent on each side of the paper. As a control, a cockroach was exposed to a piece of filter paper treated with solvent (acetone) alone. Each assay was repeated independently six times. Distribution coefficient (DC) values were calculated, a parameter that ranges between 0 (attraction) and 1 (repellence). Small nymphs were more sensitive to DEET (mean DC = 0.93). The mean DC values of the other groups varied between 0.62 (medium nymphs) and 0.71 (male adults). The group of medium nymphs was the only one whose behavior was not significantly altered by exposure to DEET. The results show the importance of assessing insect repellents at different stages of the insect's life cycle in order to obtain a complete panorama of its effect.

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Entre as espécies sinantrópicas de baratas, a barata alemã, Blattella germanica (L., 1767), é a mais importante por desenvolver altas populações em habitações. Este trabalho objetivou avaliar a mortalidade de B. germanica exposta a diferentes áreas tratadas, com quantidade equivalente de inseticidas e verificar a mortalidade provocada por inseticidas em superfícies lisa e rugosa, antes e após lavagem. Os experimentos foram conduzidos no Departamento de Fitossanidade da UNESP/FCAV de Jaboticabal, SP. No primeiro experimento, a aplicação dos inseticidas foi realizada sobre placas de Petri, com áreas de exposição ao inseticida de 25, 50, 75 e 100%. No segundo, a aplicação foi realizada com pulverizador costal pressurizado, sobre superfícies lisa (de azulejo) e rugosa (de cimento), que posteriormente foram lavadas com detergente e água corrente. Foram utilizados os inseticidas cypermethrin (Cynoff 400 PM) 2,5 g p.c./L; deltamethrin (Deltagard WG 250) 1,0 g p.c./L; lambda-cyhalothrin (Icon 5 CE) 5,0 mL p.c./L e uma testemunha sem aplicação. Foram confinadas, por quinze minutos, cinco baratas adultas no primeiro experimento e dez no segundo. As avaliações de mortalidade foram realizadas 0, 1, 2, 4, 24, 48 e 72 horas após o confinamento. Assim, conclui-se que os inseticidas aplicados em 50%, 75% e 100% das áreas resultaram em alta mortalidade de B. germanica. Os inseticidas cypermethrin , deltamethrin e lambda-cyhalothrin foram eficientes no controle de B. germanica, antes da lavagem, na superfície lisa. A eficiência de controle dos inseticidas foi maior na superfície lisa que na superfície rugosa. Após a lavagem, a eficiência diminuiu em ambas as superfícies.

Among the species of synanthropic cockroaches, the German cockroach, Blattella germanica (L., 1767) is the most important in terms of developing high populations in habitations. This study evaluated the mortality of B. germanica exposed to different areas treated with an equivalent amount of insecticides to verify the mortality caused by pesticides on smooth and rough surfaces, before and after washing. The experiments were carried out at the Departamento de Fitossanidade, UNESP/FCAV, Campus Jaboticabal, SP, Brazil. In the first experiment, the insecticide was applied to Petri dishes, with areas of exposure to the insecticide of 25, 50, 75 and 100%. The second application was performed by pressurized spraying on smooth and rough surfaces, which were then washed with detergent and water after treatment. The insecticides used were cypermethrin (Cynoff 400 AM) 2.5 c.p. g/L, deltamethrin (250 Deltagard WG) 1.0 c.p. g/L; lambda-cyhalothrin (Icon 5 EC) c.p. 5.0 mL/L and an untreated plot (control). In the first experiment, 5 adult insects were enclosed for fifteen minutes, while 10 were enclosed in the second experiment. Mortality evaluations were performed at 0, 1, 2, 4, 24, 48 and 72 hours after confinement. It was found that the insecticides used in 50%, 75% and 100% of the area resulted in a high mortality of B. germanica. The insecticides cypermethrin, deltamethrin and lambda-cyhalothrin proved efficient for the control of B. germanica, before the washing of the smooth surface. The effectiveness of these insecticides was greater on a smooth surface than a rough one. After washing, the effectiveness was lower for both surfaces.

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Microbial insecticides for cockroach control, such as those containing entomopathogenic fungi, may be an alternative to reduce contamination by chemicals in housing and food storage environments. Virulence of isolate ESALQ1037 belonging to the Metarhizium anisopliae complex against nymphs and adults of Blattella germanica (L.), and its infectivity following exposure of insects to a contaminated surface or to M. anisopliae-bait were determined under laboratory conditions. Estimated LD50 15 d following topical inoculation was 2.69 x 10(5) conidia per adult, whereas for nymphs the maximum mortality was lower than 50 percent. Baits amended with M. anisopliae conidia had no repellent effect on targets; adult mortality was inferior to 25 percent, and nymphs were not susceptible. All conidia found in the digestive tract of M. anisopliae-bait fed cockroaches were unviable, and bait-treated insects that succumbed to fungal infection showed a typical mycelial growth on mouthparts and front legs, but not on the hind body parts. As opposed to baits, the use of a M. anisopliae powdery formulation for surface treatment was effective in attaining high mortality rates of B. germanica. Both nymphs and adults were infected when this delivery strategy was used, and mycelia growth occurred all over the body surface. Our results suggest that the development of powders or similar formulations of M. anisopliae to control B. germanica may provide faster and better results than some of the strategies based on baits currently available.

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ABSTRACT Among the species of synanthropic cockroaches, the German cockroach, Blattella germanica (L., 1767) is the most important in terms of developing high populations in habitations. This study evaluated the mortality of B. germanica exposed to different areas treated with an equivalent amount of insecticides to verify the mortality caused by pesticides on smooth and rough surfaces, before and after washing. The experiments were carried out at the Departamento de Fitossanidade, UNESP/FCAV, Campus Jaboticabal, SP, Brazil. In the first experiment, the insecticide was applied to Petri dishes, with areas of exposure to the insecticide of 25, 50, 75 and 100%. The second application was performed by pressurized spraying on smooth and rough surfaces, which were then washed with detergent and water after treatment. The insecticides used were cypermethrin (Cynoff 400 AM) 2.5 c.p. g/L, deltamethrin (250 Deltagard WG) 1.0 c.p. g/L; lambda-cyhalothrin (Icon 5 EC) c.p. 5.0 mL/L and an untreated plot (control). In the first experiment, 5 adult insects were enclosed for fifteen minutes, while 10 were enclosed in the second experiment. Mortality evaluations were performed at 0, 1, 2, 4, 24, 48 and 72 hours after confinement. It was found that the insecticides used in 50%, 75% and 100% of the area resulted in a high mortality of B. germanica. The insecticides cypermethrin, deltamethrin and lambda-cyhalothrin proved efficient for the control of B. germanica, before the washing of the smooth surface. The effectiveness of these insecticides was greater on a smooth surface than a rough one. After washing, the effectiveness was lower for both surfaces.

RESUMO Entre as espécies sinantrópicas de baratas, a barata alemã, Blattella germanica (L., 1767), é a mais importante por desenvolver altas populações em habitações. Este trabalho objetivou avaliar a mortalidade de B. germanica exposta a diferentes áreas tratadas, com quantidade equivalente de inseticidas e verificar a mortalidade provocada por inseticidas em superfícies lisa e rugosa, antes e após lavagem. Os experimentos foram conduzidos no Departamento de Fitossanidade da UNESP/FCAV de Jaboticabal, SP. No primeiro experimento, a aplicação dos inseticidas foi realizada sobre placas de Petri, com áreas de exposição ao inseticida de 25, 50, 75 e 100%. No segundo, a aplicação foi realizada com pulverizador costal pressurizado, sobre superfícies lisa (de azulejo) e rugosa (de cimento), que posteriormente foram lavadas com detergente e água corrente. Foram utilizados os inseticidas cypermethrin (Cynoff 400 PM) 2,5 g p.c./L; deltamethrin (Deltagard WG 250) 1,0 g p.c./L; lambda-cyhalothrin (Icon 5 CE) 5,0 mL p.c./L e uma testemunha sem aplicação. Foram confinadas, por quinze minutos, cinco baratas adultas no primeiro experimento e dez no segundo. As avaliações de mortalidade foram realizadas 0, 1, 2, 4, 24, 48 e 72 horas após o confinamento. Assim, conclui-se que os inseticidas aplicados em 50%, 75% e 100% das áreas resultaram em alta mortalidade de B. germanica. Os inseticidas cypermethrin , deltamethrin e lambda-cyhalothrin foram eficientes no controle de B. germanica, antes da lavagem, na superfície lisa. A eficiência de controle dos inseticidas foi maior na superfície lisa que na superfície rugosa. Após a lavagem, a eficiência diminuiu em ambas as superfícies.

RESUMEN

Os objetivos deste trabalho foram o de caracterizar a resistência de Blattella germanica (L.) aos inseticidas deltametrina e clorpirifós e avaliar as relações de resistência cruzada desses inseticidas com fipronil. O isolamento da resistência foi realizado em condições de laboratório a partir de populações coletadas no campo. Três ciclos de pressão de seleção foram realizados com deltametrina e clorpirifós para a obtenção das linhagens Deltametrina-R e Clorpirifós-R. A DL50 estimada para deltametrina na linhagem suscetível (SUS) foi de 0,24 (IC 95 por cento 0,18 - 0,31) e na linhagem Deltametrina-R de 10,26 (IC 95 por cento 7,28 - 14,17) mig deltametrina/mg. Para clorpirifós, a DL50 estimada para a linhagem SUS foi de 4,16 (IC 95 por cento 2,80 - 5,33) e para a linhagem Clorpirifós-R foi de 24,98 (IC 95 por cento 20,90 - 30,28) mig clorpirifós/mg. Portanto, as razões de resistência foram de aproximadamente 43 e seis vezes para deltametrina e clorpirifós, respectivamente. Uma baixa intensidade de resistência cruzada (de aproximadamente duas vezes) foi verificada entre fipronil e os inseticidas deltametrina e clorpirifós. Sendo assim, fipronil mostrou ser viável como opção de controle em programas de manejo da resistência de B. germanica a deltametrina e clorpirifós.

The objectives of this study were to characterize the resistance of Blattella germanica (L.) to deltamethrin and chlorpyrifos and to evaluate their cross-resistance relationships to fipronil. The isolation of resistance was done under laboratory conditions from field-collected populations. Three cycles of selection pressure with deltamethrin and chlorpyrifos were conducted to obtain the Deltamethrin-R and Chlorpyrifos-R strains. The estimated LD50 for the susceptible (SUS) strain was 0.24 (IC 95 percent 0.18 - 0.31) and for Deltamethrin-R strain was 10.26 (IC 95 percent 7.28 - 14.17) mug deltametrina/mg. For chlorpyrifos, LD50 for the SUS strain was 4.16 (IC 95 percent 2.80 - 5.33) and for Chlorpyrifos-R strain was 24.98 (IC 95 percent 20.90 - 30.28) mug chlorpyrifos/mg. Therefore, the resistance ratios were approximately 43- and 6-fold to deltamethrin and chlorpyrifos, respectively. A low intensity of cross-resistance (approximately 2-fold) was observed between fipronil and the insecticides deltamethrin and chlorpyrifos. Thus, fipronil can be used as a good candidate in resistance management programs of B. germanica to deltamethrin and chlorpyrifos.