EVALUATION OF CREOSOTE FORTIFIED WITH SYNTHETIC PYRETHROIDS AS WOOD PRESERVATIVES FOR USE IN THE SEA - 2 - EFFECTS ON WOOD-DEGRADING MICROORGANISMS AND FOULING INVERTEBRATES

Colonisation of wood by marine non-boring organisms was assessed on bl ocks of Scots pine pressure-treated with: creosote, CCA plus creosote, creosote fortified with different combinations of the synthetic pyret hroids permethrin, cypermethrin and deltamethrin, and these synthetic pyrethroids in white spirit. The depth of colonisation by soft rot fun gi and tunnelling bacteria was measured. Numbers of the barnacle Balan us amphitrite and an unidentified serpulid worm on the treated blocks were counted after different exposure periods at four tropical sites i n Australia, Papua New Guinea and Singapore. Soft rot was controlled a t three sites by any treatment containing creosote, but some soft rot was detected in most treatments at Singapore. Attack of samples by tun nelling bacteria was less rapid, though most treatments were subject t o some wood cell wall deterioration. Treatments with high loadings of creosote combined with CCA had lower numbers of barnacles than other t reatments at two sites, but at Singapore, treatments of CCA combined w ith lower amounts of creosote showed no such effect. The presence of c reosote in a treatment appeared to promote barnacle settlement at Sing apore from the outset and this effect was also noted after exposure fo r more than two years at other sites that had samples treated with hig her creosote loadings. Components of creosote may mimic the effect of chemicals known to be implicated in barnacle settlement behaviour. Ini tially, the presence of creosote discouraged serpulid settlement, but after more than two years in the sea, no difference was detectable bet ween different treatments.