Amanda Grassmann da Silveira

Atividade antifúngica do extrato natural da acácia-negra à Pycnoporus sanguineus

Among the xylophagous organisms, fungi are mostly responsible for major losses in wood production. The prolonged use of chemical fungicides implies in the emergence of more resistant lines and toxicity in the environment. The goal of this study was to evaluate the toxic effect of the tannin extractive derived from the black wattle (Acacia mearnsii) on the mycelial growth of the fungus Pycnoporus sanguineus, causing white rot. Three methodologies have been developed to work with the product (sterilizing, nonsterilizing and filtering) and four concentrations (0.5, 1.0, 1.5 and 2.0%) were individually incorporated into the culture medium, evaluating the radial growth of the evaluated mycelium and results were compared with the non-treated specimen. The procedure was repeated with the methodology evaluated as being the most adequate, but increasing concentrations (3.0, 4.0 and 5.0%). The concentrations 4 and 5% were more efficient to fungal activity, and the second showed total inhibition in 50% of the plaques evaluated, also showing the smallest mycelial growth rate among all treatments tested.

Tannic extract potential as natural wood preservative of Acacia mearnsii

High toxicity of the preservatives most frequently used in wood treatment and the resulting risks of handling pose a threat to small producers and to the environment. In an attempt to mitigate these problems, the present study was conducted with the objective of evaluating the preservative effect of tannic extract on biodeterioration of Acacia mearnsii wood. For this purpose, untreated and preserved specimens, some with tannin extract and some with a preservative mixture based on CCB (Chromated Copper Borate), were submitted to accelerated rotting trials with the fungus that causes white rot (Pycnoporus sanguineus) for 16 weeks. The evaluations were made with a basis on weight loss and chemical components analysis, and they showed that the natural resistance of Acacia wood is moderate when exposed to the white rot fungus. The tannin concentrations showed similar effects to those of the CBB mixture in all evaluations, i.e., they significantly increased the biological resistance of the material, which started to be classified as very resistant to the fungus. Overall, the results suggest that tannin can be considered as a potential natural preservative product.

Ocorrência e danos de térmitas na madeira de Acacia mearnsii (Fabaceae) em dois campos de apodrecimento (Nota Científica).

RESUMO – Entender a relacao entre praga e ambiente e base para um adequado gerenciamento no setor madeireiro, assim como a busca por informacoes sobre a qualidade da madeira de especies exoticas, que sao alternativas para suprir a sua demanda. Dessa maneira, o trabalho objetivou verificar a ocorrencia e danos de termitas na madeira de Acacia mearnsii De Wild. (Fabaceae) em dois campos de apodrecimento. O experimento foi realizado em area de pastagem e de mata nativa. A avaliacao foi realizada de forma visual, com atribuicao de notas de acordo com o estado fitossanitario de cada peca. Os moiroes foram divididos em: parte subterrânea (contato com o solo) e aerea (parte do moirao situada acima do solo). Termitas atacaram somente pecas em mata nativa, nao ocorrendo danos dos insetos em area de pastagem. A influencia dos organismos foi determinada atraves do Indice de Deterioracao – I.D., onde das sete pecas da parte subterrânea presentes em mata nativa, quatro sofreram ataque moderado (I.D. = 70), uma apresentou ataque intenso (I.D. = 40), e duas, ataque leve ou superficial (I.D. = 90). Quando analisada somente a parte aerea, verificaram-se poucos danos, sendo atribuido I.D. geral de 90, ou seja, ataque leve. Os resultados foram associados as caracteristicas edafoclimaticas de cada ambiente, sendo que em mata nativa o desenvolvimento de termitas foi melhor devido a menor temperatura ambiente, maior umidade relativa do ar, menor movimentacao de ar, maior porosidade e menor densidade do solo.