Abstract Plutella xylostella (L.) is responsible for considerable vegetable crop losses in the metropolitan region of Manaus, Brazil. In recent decades, essential oils have been investigated as an alternative to synthetic insecticides. The genusPiperis widely distributed in Amazonia and essential oils from these plants have insecticidal properties. This study describes the chemical composition of the essential oils fromPiper capiterianumandPiper krukoffiias well as the lethal and sublethal effects onP. xylostella. The phytotoxicity of the oils on the host plant was also evaluated. Globulol was the major constituent of theP. krukoffiioil ando-cymene was the major constituent of theP. capitarianumoil. The oil fromP. capiterianumexhibited greater toxicity to larvae and eggs. This oil also presented greater repellant action, feeding deterrence and mild phytotoxicity to the host plant (Brassicae oleraceae). The findings suggest that this oil can be used in the preparation of a formulated insecticide for the management ofP. xylostellain different development phases. However, further studies are needed to evaluate the effect of this oil on crops under field conditions as well as non-target organisms and determine the cost-benefit ratio of a product formulated withP. capitarianumoil.

Este trabalho tem por objetivo a avaliar a influência da incorporação de finos de brita na microestrutura e nas propriedades de queima de uma massa cerâmica argilosa. As propriedades avaliadas foram: retração linear, absorção de água e tensão de ruptura à flexão. Foram preparadas composições com 0% e 25% em peso de finos de brita para a obtenção de corpos-de-prova por extrusão para queima em temperaturas de 800 a 1200ºC. A microestrutura das cerâmicas queimadas foi avaliada por microscopia ótica. Os resultados mostraram que a incorporação de finos de brita é benéfica para a produção de cerâmica vermelha possibilitando redução da retração linear e da absorção de água, sem muito efeito na resistência mecânica.

This work has as its objective to evaluate the incorporation of stone fines in the microstructure and fired properties of a clayey ceramic. The evaluated properties were: linear shrinkage, water absorption and flexural strength. Compositions were prepared with 0 and 25 wt.% of stone fines to obtain specimens by extrusion that were fired at temperatures varying from 800 to 1200ºC. The microstructure of the fired ceramics was evaluated by optical microscopy. The results showed that the incorporation of stone fines is beneficial to the production of red ceramic by decreasing both the linear shrinkage and the water absorption, without much effect on the mechanical strength.