Juarez Benigno Paes

Natural resistance of nine woods of Brazilian semi-arid region to wood-destroying fungi under laboratory conditions

The objective of this research was to evaluate the natural resistance of nine semi arid region Brazilian woods to wood-destroying fungi under laboratory conditions. The studied woods were the Prosopis juliflora, Anadenanthera macrocarpa, Myracrodruon urundeuva, Schinopsis brasiliensis, Senna siamea, Tabebuia aurea, Amburana cearensis, Tabebuia impetiginosa and Aspidosperma pyrifolium. Test samples measuring 2.54 x 2.00 x 1.00 cm, with the largest measure taken fiber-wise were obtained from four pith-to-bark positions. The samples were submitted to action of the Postia placenta and Neolentinus lepideus fungi for 14 weeks. Species resistance, with exception of those of Prosopis juliflora and Anadenanthera macrocarpa (P. placenta), Tabebuia aurea (N. lepideus) and Senna siamea (P. placenta and N. lepideus), was affected by pith-to-bark position, not been associated to density wood. The Tabebuia impetiginosa wood and the heartwood of Myracrodruon urundeuva and Schinopsis brasiliensis showed the greatest resistance to the tested fungi. The natural resistance disparity, except in Myracrodruon urundeuva and Schinopsis brasiliensis, has not been associated to content of soluble substances in hot-water present in the wood of each species studied.

Eficiência do CCB na resistência da madeira de algaroba (Prosopis juliflora (Sw.) D.C.) em ensaio de apodrecimentoacelerado

The objective of research was to analyze the Osmose CCB preservative efficiency to improve the wood Prosopis juliflora (Sw) D.C. resistance to Postia placenta fungus. In order to meet the objectives proposed, round pieces of P. juliflora were treated by sap displaced method in 1; 2 and 3% of active ingredients of CCB solutions, by 3, 6, 9, 12 and 15 days. Wood disks were obtained at three positions (50 cm from the base, middle and top) of the treated pieces. CCB penetration and retention were analyzed at these positions, as well as the resistance to P. placenta fungus (accelerated laboratory test decay) It was found better penetration and retention in pieces submitted to 2% of CCB solutions. The CCB penetration and retention, as well as the resistance of treated wood, in general, decreased from base to top of pieces. The preservative treatment conferred high-level resistance against P. placenta fungus to P. juliflora pieces. This has not occurred only for samples from the top (1% CCB and 15-day treatment; 2% and 9 days; 3% and 3, 12 and 15 days) and from the middle of pieces (3% CCB and 3 and 12-day treatment), which were classified as resistant.

Resistência natural de nove madeiras do semiárido brasileiro a fungos xilófagos em simulares de campo

The objectives of this research were to evaluate the natural resistance of nine woods from the Brazilian semi-arid region to fungi under field simulator condition and to correlate the wood natural resistance with the wood density and the content of extractives soluble in hot water. The studied woods were Prosopis juliflora, Anadenanthera colubrina var. cebil, Myracrodruon urundeuva, Schinopsis brasiliensis, Senna siamea, Tabebuia aurea, Amburana cearensis, Tabebuia impetiginosa and Aspidosperma pyrifolium. Test samples measuring 0.5 x 1.5 x 15.0 cm, with the largest measure taken on fiber direction, were obtained from four positions on pith to bark direction in the stem. The samples were submitted to the action of natural micro-flora of three soils; forest, agricultural use and gramineous plant soils, for 180 days. Wood resistance to decay was affected by the bark-heart wood position. Just for M. urundeuva, the wood resistance was associated to wood density and extractives content soluble in hot water. The resistance of P. juliflora, A. columbrina, T. aurea, and T. impetiginosa woods was not associated to density nor the extractive content. The sp-wood was the most attacked position for all soils. Among the tested soils, the one for agricultural use presented the lowest biological activity, presenting lower deterioration for the tested woods.

Resistência de painéis aglomerados produzidos com diferentes proporções de madeira e casca de arroz a fungos e cupins xilófagos

Decay resistance against fungi and termite of particleboard made with different proportions of woodxa0 ( Eucalyptus grandis ) and rice husk was studied. Particleboard with 0, 20, 40, 60, 80 and 100% proportions of rice husk was produced using urea-formaldehyde and tannin-formaldehyde as adhesives. Particleboards produced with rice husk presented a higher resistance against fungi and termite attack. Particleboards glued with tannin-formaldehyde were more resistant to the attack of termites; for fungi, the difference between adhesives was observed when these particleboards were submitted to the attack of Gloeophyllum trabeum , in which case the particleboards produced with urea-formaldehyde were more resistant. Trametes versicolor was the fungus that caused the largest mass loss to the particleboards.