Controlling internal decay of preservative-treated utility poles
1996
Giron, M.Y. | San Pablo, M.R. | Morrel, J.J. (Forest Products Research and Development Inst., College, Laguna (Philippines). Protection and Preservation Section)
Two methods of controlling internal decay in preservative-treated, standing utility poles were evaluated: application of fumigants and bandage wrap + vapam. To determine the retreatment cycle, core samples were extracted at yearly intervals in 4 years. These were bioassayed through the closed tube technique using Fomes lividus as the test decay fungus. Decay fungi were observed on 50 percent of the standing preservative-treated poles that have been in service for 10 years in Metro Manila. Poria sp. was isolated from most of the poles with internal decay and was found to cause considerable weight loss in apitong (Dipterocarpus grandiflorus Blanco), red lauan (Shorea negrosensis Foxw.), white lauan (Shorea contorta Vid.) and tangile [Shorea polysperma (Blanco) Merr.]. Penicillium sp., Aspergillus niger, Trichoderma viride, Alternaria sp., and Curvularia inaequalis comprised 45 percent of the isolates. The population of decay fungi was observed to be very frequent at the groundline but decreased toward the poles' top. The efficacy of creosole, sodium pentachlorophenate (NaPCP), vapam, vorlex and methylisothiocyanate (MITC) and chloropicnien varied. However, complete inhibition of fungal growth was noted in test blocks when chloropicnien and MITC were applied at 125 ug/cc and 50 ug/cc, respectively, per wood block. Field test revealed that vapam and MITC persisted for 3 years as shown by the inhibition of growth of F. lividus fungus in the bioassay tubes. Bandaging and the application of vapam or MITC markedly reduced growth of the fungus
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