Effectiveness of wood preservatives and treatments against marine borers in Philippine waters
F R Siriban, M G Laxamana, P G Mata
A 5-year exposure test was conducted on the effectiveness of wood preservatives and treatments against marine borers in Philippine waters. Air-dried heartwood samples of apitong (Dipterocarpus grandiflorus) 76.2 x 88.9 x 609.6 mm³ (3 x 3.5 x 24 in³) in size were pressure treated with coal tar creosote and two types of CCA (copper/chrome/arsenic) and CuCZA (copperized chromated zinc arsenate) waterborne preservatives. Average retention for creosote was 232.8 kg/m³ (14.5 lb/ft³). The dry salt retentions for the water-borne preservatives were CCA (A) 6.74 and 9.14 kg/m³; CCA (B) 8.01 and 12.04 kg/m³; and CuCZA 6.13 and 9.33 kg/m³ respectively. The first set of these treated specimens including untreated controls was exposed to marine borers at the Philippine Navy Ship Repair Yard in Cavite City in 1961 and another set a year later. Inspections were made at 6-monthly intervals. Preservatives CCA (A) and CuCZA at the two retention levels used and CCA (B) at the higher retention favourably oompared in performance with creosote at 14.5 lb/ft³ against marine borer infestations. The untreated apitong specimens incurred 75% deterioration after 9 months while the treated specimens attained the same degree of attack after 3.5 to 4.75 years. One of the CCA preservatives and creosote used in double-treating wooden test frames appeared to have conferred better protection than any of the water-borne preservatives tested. Martesia borers were more destructive and active than Limnoria in the test site. Martesia were active throughout the year, while the Limnoria appeared prevalent during the warmer months.