Correlação entre teores de extrativos e a resistência natural de quatro madeiras a cupins xilófagos.

Abstract

Correlation between extractive contents and the natural resistance of four woods to xylophagous termites. The objective of the research was to correlate the natural resistance of four woods to the attack of the xylophagous termite (Nasutitermes corniger Motsch) with the amount of extractives and ash present in the chemical composition of the tested species. The woods evaluated were angico (Anadenanthera colubrina var cebif), craibeira (Tabebuia aurea), cumaru (Amburana cearensis) and eucalyptus (Eucalyptus camaldulensis). Specimens measuring 2.00 x 10.16 x 0.64 cm were taken from each species in two positions (heartwood and sapwood). The samples were exposed to the action of termites for 45 days in a food preference test. The extractive content of the woods was obtained by means of sawdust that passed through a 40 sieve and was retained in a 60 mesh. Natural resistance was not associated with the extractive content present in the wood. The wood most resistant to termite attack was angico in both positions (heartwood and sapwood) and eucalyptus wood showed the greatest wear. The ash content was correlated with the resistance of the woods, that is, the species that presented the highest contents was the most resistant to the attack of termites.