Fungitoxicity of Sulfuryl Fluoride to Ceratocystis fagacearum -In Vitro and in Wilted Red Oak Log Sections. R. P. Woodward, Postdoctoral Research Associate, Department of Forest Products, University of Minnesota, St. Paul 55108. E. L. Schmidt, Professor, Department of Forest Products, University of Minnesota, St. Paul 55108. PLANT DIS. 79:1237. Accepted for publication 5 September 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1237.

The European Union requires imported red oak logs to be fumigated with methyl bromide to eradicate the oak wilt fungus, Ceratocystis fagacearum. The restriction of methyl bromide would threaten the export of oak, as other fumigants have not been evaluated. Sulfuryl fluoride penetrates wood and has been used extensively for insect control, but fungicidal effects are unknown. The effect of sulfuryl fluoride exposure on 10-day-old C. fagacearum cultures was tested in a closed circuit fumigation chamber at concentrations of 16, 40, 60, 80, 100, and 120 g/m3 for 24 and 48 h. Rates of 80 g/m3 for 48 h and 120 g/m3 for 24 h rendered cultures unable to grow. When stained with Janus Green B, both mycelia and conidia were nonviable. End-sealed log sections from wilted red oak trees were fumigated at 160, 220, and 280 g/m3 for 72 h. Eradication of C. fagacearum from red oak log sections was achieved after exposure to 280 g/m3 for 72 h. (concentration ? time product = 18,530 g h/m3). Graphium, Veriicillium, and Paecilomyces spp. (also isolated initially) were eradicated after the 18,530 g h/m3 treatment. This is the first report of fungitoxicity of sulfuryl fluoride.

Keyword(s): Quercus rubra