Sapstain and mould of pine timber: field screening of pine species and preventative chemicals
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Freshly cut and sawn timber of Pinus elliottii, P. patula and P. taeda was dipped in one concentration of Stopstain (a boric acid based chemical) and several concentrations of Antiblue (active ingredient sodium pentachlorophenate) following a standard ten-minute immersion time and stacked in the open at Martin Sawmill, Chimanimani during the wet season. The timber was assessed for stain and mould development four or five weeks later. P. elliottii was most susceptible to stain and mould fungi, P. taeda moderately so and P. patula least. Antiblue in the range 2,5-4,0 per cent concentration was the better of the chemicals, providing adequate control of causal fungi on the three pine species. The recommended rate of 5,0 per cent Stopstain gave results slightly better than the control. A similar experiment had been conducted during the wet season at Chisengu Sawmill, Chimanimani, using Antiblue and P. elliottiitimber. A concentration of 2,0 per cent provided 91 per cent control and 3,0 per cent gave complete control against stain and mould fungi. The results indicate the need to vary concentrations of preservative chemicals depending on weather conditions, in particular rainfall amount and distribution. Broad interim recommendations to minimise stain and mould development on pine timber in Zimbabwe are provided.