Unseasoned export lumber sawn in British Columbia currently is treated with aqueous anti-sapstain formulations, applied by relatively inefficient hydraulic spray systems. As an alternative spray system ICI's Electrodyn (ED) applying PP523, an organic solvent-based formulation containing 5% hexaconazole as the active ingredient, had been previously tested at Forintek in field trials. Recent development work showed that a bipolar apparatus using twelve ED nozzles could uniformly treat lumber to the required retention levels at transfer efficiency as high as 60%. To prove the commercial potential of the improved ED system, the PP523 formulation was applied at two levels of treatment on a large quantity of lumber for a shipping trial. Earlier field trials indicated that a retention of 25-30 μg hexaconazole/cm2 was required for acceptable protection. Included in the current test was a set of untreated control lumber and a set treated with the aqueous formulation NP-1 applied by a conventional hydraulic spray system; one of the two active ingredients of NP-1 is didecyl dimethyl ammonium chloride (DDAC), and treatment was done to the recommended level of 90μg DDAC/cm2. One lot of lumber was shipped to Tampa, Florida, for storage and another kept in Vancouver, British Columbia; both lots were inspected four and one-half months after treatment and rated for the extent of fungal degradation.
All untreated lumber, both in Tampa and in Vancouver, was degraded by staining fungi and moulds so that only 32% and 48%, respectively, was rated as acceptable. In all sets treated with PP523, applied to 20μg and 30μg hexaconazole/cm2, lumber was protected to better than 90% acceptability. Although the lumber treated with NP-1 was rated at 96% acceptability in the Vancouver-stored lumber, the Tampa-stored lumber was rated at only 82% acceptability. The 90% acceptability figure, determined by a rating system in use for a number of years at Forintek, has become an international norm. This successful shipping trial of an ED system applying PP523 to lumber propelled at sawmill production line speeds, and subjected to rigorous export storage conditions, indicates the ED system should next be developed for a sawmill installation.