PERFORMANCE OF UNMODIFIED AND COPPER-MODIFIED ALKYLAMMONIUM-TREATED STAKES IN GROUND CONTACT

Pinus radiata D. Don sapwood stakes treated with two unmodified and two copper-modified alkylammonium compounds were examined during 4 years' exposure in the Whakarewarewa "graveyard". The stakes treated with benzalkonium chloride (10.6 kg/m3) and dialkyldimethyl ammonium chloride (6.2kg/m3) have been colonised and attacked by brown-rot, soft-rot, and white-rot fungi. Stakes treated with these chemicals modified by the addition of a cupric salt were in better condition. The modified treatments partially controlled white rot but treated stakes remained susceptible to soft rot and an unsightly brown erosion. This erosion is thought to be caused by brown-rot fungi. Although none of the four treatments examined is suitable for approval as a groundline treatment, copper modification still offers potential for this end-use and further formulation studies are considered worthwhile