In the Pacific Northwest, freshly peeled Douglas-fir poles are often air-seasoned for 6 to 24 months before preservative treatment. The ability of ammonium bifluoride (ABF) to limit fungal colonization was evaluated by flooding pole sections with saturated solutions of ABF before air-seasoning them for 1, 2, or 3 years at site in Oroville, California; Eugene Oregon; Scappoose, Oregon; and Arlington, Washington. Each year, selected poles were destructively sampled to determine levels of fungal colonization. The results indicate that ABF substantially reduced those levels, especially at the driver, southermost site. ABF treatment can reduce, but not eliminate, the risk of fungal colonization during air-seasoning.