Birch and pine stakes treated with chromated copper arsenate and didecyldimethylammonium chloride were incubated in two soils in a "Fungus Cellar" test. At three month intervals, sets of stakes were inspected and assigned visual ratings or removed from the soil beds for weight loss determination. Preliminary results after nine months exposure have shown differences in the decay rates between birch and pine and also between soils. Overall, the decay rate for pine, treated and untreated, has been considerably lower than birch in both soils. A Michigan soil accelerated the decay rates up to 3 times that observed for a Florida soil. Soil type also influenced the primary decay present in the stakes. Basidiomycete attack was observed in birch stakes treated with subthreshold retentions of both preservatives in the Michigan soil, while the primary decay in the Florida soil was soft rot. Untreated birch controls failed through basidiomycete attack in both soils. Soft rot was the primary decay in treated and untreated pine for both soils. However, more data is needed to determine if this trend will continue. Weight losses as low as 9.3% caused stake failure (visual ratings of 0). Basidiomycete damage caused stake failure at lower weight losses than soft rot. Regardless of the decay type, threshold retentions selected by weight loss or visual ratings were similar.

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