Acaricidal and insecticidal effects of essential oils against ectoparasites of veterinary importance / Efectos acaricidas e insecticidas de los aceites esenciales contra los ectoparásitos de importancia veterinaria

Ectoparasitism in animals has become an issue of great concern that needs to be resolved to prevent huge economic losses occurring to livestock industry all over the world. Synthetic adrugs have been playing a major role in controlling ectoparasites, but their frequent and irrational use has resulted in drug resistance to routinely used chemicals and their residual effects on food and environment. Therefore, this approach of using chemical acaricides and insecticides is losing its popularity and effectiveness in controlling ectoparasites. So, the development of alternative approaches in ectoparasite management is currently required. Among alternative protocols, plants and their essential oils have played remarkable role in controlling different ectoparasites (ticks, flies, mites, lice) of veterinary importance. Essential oils have been proved to be cheaper, more effective and safer therapeautic agents against different ectoparasites of livestock importance.

En los animales el ectoparasitismo se ha convertido en un tema de gran preocupación que debe resolverse para evitar que se produzcan grandes pérdidas económicas para la industria ganadera en todo el mundo. Los aditivos sintéticos han desempeñado un papel importante en el control de los ectoparásitos, pero su uso frecuente e irracional ha dado como resultado la resistencia a los fármacos utilizados habitualmente y efectos residuales sobre los alimentos y el medio ambiente. Por lo tanto, el enfoque basado en el uso de acaricidas e insecticidas químicos está perdiendo popularidad y efectividad en el control de los ectoparásitos. Por lo tanto, actualmente se requiere el desarrollo de enfoques alternativos en el manejo de ectoparásitos. Entre los protocolos alternativos, las plantas y sus aceites esenciales han jugado un papel notable en el control de diferentes ectoparásitos (garrapatas, moscas, ácaros, piojos) de importancia veterinaria. Se ha demostrado que los aceites esenciales son agentes terapéuticos más baratos, más efectivos y más seguros contra diferentes ectoparásitos de importancia ganadera.

Juvenile hormone activity in Dysdercus cingulatus Fabr by juvenile hormone esterase inhibitor, OTFP.

Application of juvenile hormone esterase inhibitor 3-octylthio-1,1,1- trifluropropan-2-one (OTFP) to 5th instar nymphs and virgin females of D. cingulatus revealed the profound role played by juvenile hormone esterase (JHE) in metamorphosis and reproduction. The ability of OTFP to cause delay and the formation of malformed nymphs, suggests that inhibition of JHE in vivo maintains a higher than normal hemolymph JH titer. It is obvious that OTFP does inhibit in vivo JHE activity in late instar nymphs. Further, the application of JHE inhibitor, OTFP to virgin females demonstrates that substituted trifluropropanones can indirectly stimulate egg development by inhibiting JHE activity in virgin females.

Effects of an oil spill and discharge of domestic sewage on the insect fauna of Cururu stream, Manaus, AM, Brazil

As assembléias de insetos aquáticos e edáficos de três igarapés da Amazônia Central foram utilizadas para avaliar o impacto sofrido por um deles (igarapé Cururu), após um vazamento de óleo derivado de petróleo, ocorrido em agosto de 1999. O igarapé Cururu já era impactado pelo despejo de esgoto doméstico. A avaliação desses sistemas foi realizada em quatro diferentes períodos do ciclo hidrológico da região (vazante, seca, enchente e cheia), entre setembro de 2000 e maio de 2001. Os insetos foram coletados com draga Eckman, rede entomológica aquática e trado, e utilizados para estimar a riqueza taxonômica (nível de família) e a densidade de insetos em cada sistema. Os efeitos de anóxia e os efeitos da eutroficação foram mensurados pelas médias de concentração de oxigênio dissolvido, nitrogênio total e fósforo total, estimadas nos três sistemas. A riqueza e abundância da fauna de insetos foram maiores no igarapé Cristalino (não impactado) do que nos igarapés Bom Jardim (impactado pelo despejo de esgoto) e Cururu, com exceção das amostragens de insetos litorâneos. A concentração do oxigênio dissolvido no igarapé Cururu foi menor do que nos outros dois sistemas, enquanto as concentrações de nitrogênio total e fósforo total no igarapé Cururu foram maiores. Esses elementos tiveram valores inversos no igarapé Cristalino e intermediários no igarapé Bom Jardim. As concentrações de oxigênio dissolvido, nitrogênio total e fósforo total refletem as modificações provocadas pela eutroficação antropogênica nos sistemas Bom Jardim e Cururu. Isso ocorreu devido à liberação de efluentes domésticos pelas comunidades locais e pelo óleo introduzido no igarapé Cururu, influenciando negativamente a riqueza e abundância de insetos nesses igarapés.

Modulatory influence of juvenile hormone analogue (JHa) and 20-hydroxyecdysone on lipophorin synthesis in red cotton bug, Dysdercus cingulatus Fabr.

Topical supply of methoprene, a juvenile hormone analogue (JHa) caused notable morphological disturbance in insects. Topical supply of methoprene to newly emerged adult female D. cingulatus caused notable disturbance and induced a dramatic reduction in the total haemolymph protein pattern and lipophorin production in tissues like fat body, ovary and haemolymph. Total protein concentration in haemolymph also showed significant reduction in 1 day old insects but increased slightly as age advanced. Application of 20-hydroxyecdysone (20-HE) to 2-day-old adult female stimulated protein synthesis intensively. Lipophorin levels in fat body and ovary also simultaneously increased. Densitometric analysis revealed that methoprene inhibits while 20-HE stimulates lipophorin production in D. cingulatus.

Electroantennogram responses of Chrysoperla carnea (Stephens) to volatiles.

Electrophysiological responses of adult males and females of C. carnea to commonly occurring plant volatiles were recorded using the electroantennogram technique. Responses to 28 volatiles evaluated indicate that both depolarization and recovery to the baseline were rapid in females compared to males. Normalized EAG responses relative to the standard, trans-caryophyllene reveal significant differences between the chemicals as also between the sexes. The response of males to several of the compounds, particularly the terpenoids was higher than females. The pooled averages to the different classes of chemical compounds reveal greater response for fatty acid derivatives and terpenoids, particularly the oxygenated monoterpenes and the sesquiterpenes. These findings are discussed in relation to volatiles released in the cotton ecosystem.

Hormonal implication in Bracon-venom-induced paralysation of the host larva of Corcyra cephalonica (Lepidoptera: Pyralidae).

To facilitate oviposition, the ectoparasite Bracon hebetor, injects its venom, a paralysing toxin, to the host Corcyra larva that ultimately dies without showing any metamorphic change, even if allowed to remain unparasitised. At the initial stage of venom injection the rate of heartbeat of the host becomes abruptly high. This has been explained from the synergistic action of the substances of poison gland and calyx. The paralysed larvae subsequent to envenomization die within 240 hr. Application of hydroprene as single dose or with a booster dose after paralysation mostly increases the survival period considering heart beat as the index. The predicted value of survival period (714.4 hr), determined from a fitted equation obtained from the relationship between heart beat and survival period, indicates that a 100 microg treatment/larva with a booster dose of 50 microg/larva most effectively lengthens the period. It is concluded that the venom-induced physiological dysfunction of the immobilised larvae, as indicated in the rate of heart beat and survival period, though can be recovered to some extent after the application of juvenoids, there cannot occur any metamorphic change of these larvae. The parasitoid, therefore, succeeds in completing its development and metamorphosis by arresting the development of its host through an indirect hormonal suppression. The findings indicate an endocrine implication in host-parasite relationship in insect.

Aspectos moleculares de la resistencia a insecticidas / Molecular basic of insecticide resistance

El surgimiento de resistencia en poblaciones de insectos es uno de los efectos indeseables asociados al uso de insecticidas, y es un buen ejemplo del modo en que ocurren los procesos microevolutivos. En 1908 se documentó por primera vez la existencia de insectos resistentes a insecticidas. Ahora se conocen casos de resistencia en más de 500 especies de artrópodos. Los principales mecanismos que confieren resistencia a insecticidas son penetración cuticular reducida, metabolismo degradativo aumentado y reducción en la susceptibilidad de los sitios de acción. Los métodos de la biología molecular permiten identificar las bases moleculares de esos mecanismos. El propósito de este artículo es reseñar el conocimiento disponible acerca de la biología molecular de la resistencia a insecticidas: mutaciones puntuales en genes de acetilcolinesterasa (Drosophila melanogaster) y del receptor de GABA (varias especies), inserciones en genes de transferasas (D. melanogaster) y del citocromo P450 (D. melanogaster), amplificación de genes de esterasas (Myzus persicae y Culex pipiens / quinquefasciatus complex), cambios que afectan la expresión del gen del citocromo P450 (Musca domestica), y una mutación ligada al gen del canal de sodio dependiente de voltaje (M. domestica)

Bioinsecticide action of the venom of africanized bees Apis mellifera Linnaeus 1758 (hymenoptera: apidae): I-the most susceptible age of diatrae saccharalis fabricius 1794 (Lepeletier: pyralidae) eggs to the venom action

The present paper aimed at testing the action of non-lyophilized venom of Africanized bees Apis mellifera through topical applications on Diatraea saccharalis egg masses. The CL50, DL50 and the most susceptible age of eggs to the venom topic application were also determined. Three-day-old eggs were the most susceptible to the venom action with CL50 equal to 8.6 mg/ml and DL50 equal to 0.173 mg/mass. The venom loses its action after being stored for 15 days.

Survival, developmental and morphogenic deficiencies of parasarcophaga argyrostoma [diptera: sarcophagidae] induced by the biosynthesis inhibitor chlorfluazuron [IKI-7899]

To evaluate the activity of benzoylphenyl urea chitin biosynthesis inhibitor chlorfluazuron [IKI-7899] against Parasarcophaga argyrostoma, 7 doses were topically applied [once] onto early third [last] instar larvae, puparia, or newly pupa: 150, 100, 50, 10, 1, 0.5 and 0.25 mug/insect. After topical treatment of last instar larvae, the highest morality was caused by both highest dose and the lowest mortality was caused by the lowest dose. The lethal activity of IKI-7899 pronouncedly decreased as the treatment was lately carried out [at the puparial time]. IKI-7899 failed to cause cumulative mortality because no pupal or adult mortalities were observed, irrespective of the time of treatment. Treated larvae suffered the action of IKI-7899 because they had decreased weight gain. Except the lowest dose, the weight gain of larvae inversely correlated with the dose levels. IKI-7899 prolonged not only the larval duration, but also the pupal duration after topical treatment of last instar larvae with doses 50 - 0.25 mug/larva. With no exception, all doses topically applied onto puparia or newly formed pupae enhanced pupae to live longer. Topical application onto last instar larvae resulted in different degrees of reduction of pupation rate, but IKI-7899 could not affect the pupal morphogenesis after larval treatment except by its highest dose, which led to 8.33% pupal deformities and 7.69% larval-pupal intermediates. The dose 100 mug/larva topically applied onto last instar larvae obtained 7.69% permanent larvae, which suffered from the action of compound along 16 days and eventually perished without any external feature of puparium formation. A metamorphic effect of IKI-7899 pronouncedly appeared in the adult stage. Three higher doses completely arrested the adult flies

Controle da cigarrinha-verde (Empoasca kraemeri (Ross & Moore, 1957) (Hemiptera - Homoptera: cicadellidae)) no feijoeiro (Phaseolus vulgaris) / Control of cigarrinha-verde (Empoasca kraemeri (Ross & Moore, 1957) (Hemiptera - Homoptera: cicadellidae)) in the beans (Phaseolus vulgaris)

Estudou-se os efeitos tóxicos dos inseticidas esfenvalerato, fenitrotion, fenpropatrin e monocrotofos sobre as ninfas de E. kraemeri em cultura de feijoeiro. A pesquisa doi conduzida no município de Nepomuceno - MG, utilizando uma lavoura comerical de cultivar "Carioca". Os compostos foram diluídos em água nas doses recomendadas pelos fabricantes para o controle de pragas, sendo a aplicaçäo realizada através de um pulverizador costal, propiciando volume de aplicaçäo de 400 L/ha. Os resultados mostraram que todos os compostos controlaram a praga em questäo, porém o fenitrotion na dose de 750 g i.a./ha apresentou o maior nível médio de controle.

Histochemical studies on the effect of propoxur on yolk synthesis in the ovarioles of the blow fly, chrysomyia albiceps [Wiedemann] [diptera: calliphoridae]

The effect of the carbamate insecticide, propoxur, on yolk synthesis in the ovarioles of the blow fly, Chrysomyia albiceps [Wiedemann] was studied. Histochemical studies showed that DNA, RNA, protein and lipid synthesis in propoxur-treated ovarioles decreased as compared with that in non-treated ovarioles, with some deteriorations in the chromatin in the nuclei of some nurse cells. On the other hand, the synthesis of carbohydrate is more or less not affected

Therapeutic action of acetylcholine in malathion toxicity.

Administration of malathion to the developing Philosamia ricini larvae induces accumulation of acetylcholine, marked inhibition of acetylcholinesterase activity, depletion of all nutrients, heavy weight loss and high mortality. Pre-treatment of the larvae with acetylcholine via feed, reduces malathion toxicity and conversely, feeding of acetylcholine to malathion-treated larvae reverses the toxic effects. Resumption of normal control feed to malathion-treated insects results in higher mortality than in insects fed acetylcholine after exposure to malathion. This emphasizes the therapeutic action of acetylcholine. Feeding of a mixture of equal quantities of malathion and acetylcholine recorded significantly lower mortality among insects in comparison to those fed malathion alone. This further supports the protective action of acetylcholine. Reversal of malathion toxicity and the protective action of acetylcholine have been attributed to the mediation of choline, an essential insect vitamin that gets released as a catabolic product of acetylcholine.