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[en] The main objectives of the present study are to introduce new, ecologically safe, and natural compounds for controlling red flour beetle, Tribolium castaneum, and to understand the possible mode of action of these compounds. Therefore, the insecticidal and repellent activities of two phenylpropenes and six monoterpenes have been evaluated against the adults of T. castaneum. The inhibitory effects of these compounds on the activity of adenosine triphosphatases (ATPases) and acetylcholinesterase (AChE) were also tested. In fumigant toxicity assay, (−)-terpinen-4-ol (LC50 = 20.47 μl/l air) and α-terpinene (LC50 = 23.70 μl/l air) exhibited the highest toxicity without significant differences between them. Moreover, (−)-menthone and p-cymene showed strong toxicity, while (−)-citronellal, trans-cinnamaldehde, and eugenol were not active. In contact toxicity assay, the two phenylpropenes, trans-cinnamaldehde and eugenol, had the highest toxicity with same LC50 value of 0.02 mg/cm2. The monoterpenes and phenylpropenes showed pronounced repellent effect on the adults of T. castaneum at 0.001 mg/cm2 with (−)-menthone, trans-cinnamaldehyde, and α-terpinene being the most effective after 2 h of exposure. Repellent activity depended on compound, exposure time, and concentration. On the other hand, the tested compounds exhibited strong inhibition of ATPases form the larvae of T. castaneum as their IC50 values ranged between 1.74 and 19.99 mM. In addition, (−)-citronellal (IC50 = 9.82 mM) and trans-cinnamaldehde (IC50 = 23.93 mM) caused the highest inhibitory effect on AChE, while α-pinene (IC50 = 53.86) and p-cymene (IC50 = 68.97 mM) showed the weakest inhibitory effect. The results indicated that the tested phenylpropenes and monoterpenes had the potential to be developed as natural insecticides and repellents for controlling T. castaneum.
[en] To study the effect of gamma irradiation on deltametrina, malathion and fenitrothion, the saturated filter paper technique was used. The filter paper, saturated with the products, was submitted to increasing doses of gamma radiation - 10, 20 and 40 kGu at a 12.76 kGy rate p/h. Adults of Sitophilus zeamais Mots. reared at 250 +- 10C and relative humidity of 70 +- 5% were used. The dead rate used and life expectancy was calculated using the best regression as indicator of the degradation factor of the insecticide. It was noted that gamma radiation degraded deltametrina and fenitrothion, the latter more markedly at a 40 kGy dose. Gamma radiation had no effect on malathion and the insects submitted to it showed a life expectancy smaller than the controls. (author)
[pt]Este trabalho teve por objetivo estudar a degradacao dos inseticidas: deltametrina, malathion e fenitrothion utilizando-se a tecnica de impregnacao de papel de filtro aos inseticidas e submetidas a doses crescentes de radiacao gama de 10, 20 e 40 kGy sob uma taxa de dose de 12,76 kGy por hora. Para realizacao do experimento utilizaram-se adultos de Sitophilus zeamais Mots. de uma criacao normal mantidos a condicoes de +- 10C de temperatura e umidade relativa de 70 +- 5%, como animais indicadores da degradacao dos inseticidas. Com os resultados das esperancas de vida dos insetos calculou-se as melhores regressoes segundo o criterio do melhor coeficiente de correlacao. Observou-se que as radiacoes gama degradaram os inseticidas deltametrina e fenitrothion, porem para este ultimo a degradacao foi mais acentuada na dose de 40 kGy. Quanto ao malathion as radiacoes gama nao o degradaram, sendo que os insetos a ele submetido apresentaram esperanca de vida (exo) menor que a testemunha. (autor)
[en] We expressed rat Nav1.6 sodium channels in combination with the rat β1 and β2 auxiliary subunits in Xenopus laevis oocytes and evaluated the effects of the pyrethroid insecticides S-bioallethrin, deltamethrin, and tefluthrin on expressed sodium currents using the two-electrode voltage clamp technique. S-Bioallethrin, a type I structure, produced transient modification evident in the induction of rapidly decaying sodium tail currents, weak resting modification (5.7% modification at 100 μM), and no further enhancement of modification upon repetitive activation by high-frequency trains of depolarizing pulses. By contrast deltamethrin, a type II structure, produced sodium tail currents that were ∼ 9-fold more persistent than those caused by S-bioallethrin, barely detectable resting modification (2.5% modification at 100 μM), and 3.7-fold enhancement of modification upon repetitive activation. Tefluthrin, a type I structure with high mammalian toxicity, exhibited properties intermediate between S-bioallethrin and deltamethrin: intermediate tail current decay kinetics, much greater resting modification (14.1% at 100 μM), and 2.8-fold enhancement of resting modification upon repetitive activation. Comparison of concentration-effect data showed that repetitive depolarization increased the potency of tefluthrin ∼ 15-fold and that tefluthrin was ∼ 10-fold more potent than deltamethrin as a use-dependent modifier of Nav1.6 sodium channels. Concentration-effect data from parallel experiments with the rat Nav1.2 sodium channel coexpressed with the rat β1 and β2 subunits in oocytes showed that the Nav1.6 isoform was at least 15-fold more sensitive to tefluthrin and deltamethrin than the Nav1.2 isoform. These results implicate sodium channels containing the Nav1.6 isoform as potential targets for the central neurotoxic effects of pyrethroids.
[en] This review outlines the major achievements in design of novel chemical insecticides and acaricides, especially those with non-standard mechanisms of action, viz., neonicotinoids and oxidative phosphorylation decouplers. The bibliography includes 119 references.
[en] Plants produce a plethora of chemical compounds that can be used for various applications. Philippines is one of the mega-diverse country in the world in terms of its fauna na flora. Today different plant sepcies are being tapped as source of natural products that can be used to develop greener solutions vis-a-vis synthetic ones. This study used traditional fruit bearing fauna, Annona squamosa L. and Mangifera altissima B. to screen for biological activity against the tropical cocount pest, Brontispa longissima G. Organic preparations via reduced vacuo from seeds of these plant species were evaluated. In vitro-assays performed revealed that the selected organic preparations of M. altissima and A. squamosa were comparable to synthetic formulation. These were further evaluated under stimulated conditions at the screening facility of the Philippine Coconut Authority -Albay Research Center. Organic formulations have also shown less adverse biological effects on non-target species such as parasitoid, Tetrastichus brontispae F. (Hymenoptera: Eulophidae). Hence, data from plants with potential for applications in agriculture and other key sectors of the country. (author)
[en] The distribution of carbofuran (2,2-dimethyl 2,3-dihydrobenzofuranyl 7-N methyl carbonate) in the rice plant was studied by using 14-C3 labelled carbofuran. Study was conducted for the whole plant as well as ground plant. Results obtained show than ground plants materials absorbed carbofuran and the equilibrium was reached after four hours of shaking. The distribution constant were 20 : 1 for stem and root, and 10 : 1 for leaves. Carbofuran was absorbed by plant root through water absoption metabolism. Carbofuran absorbed by plant was proportional with plant weight. Radioactivity of 14-C was higher in plant roots and leaves than stems. For the leave, it was more concentrated in the tip. (author). 3 refs, 1 fig, 3 tab