Propiconazole as a Treatment for Oak Wilt in Quercus rubra and Q. ellipsoidalis

Abstract

In Minnesota, propiconazole was injected into mature Quercus rubraand Q. e///pso/tfa//sat high risk to natural infection with Ceratocystis fagacearum, the oak wilt fungus. The trees were treated preventively in 1989 and 1990 at a constant rate of 0.168 g a.i./cm dbh using a root flare injection technique. Control trees were left untreated. Since 1989,15 of 49 trees treated in 1989 have wilted in comparison to 18 of 50 control trees. Nine of 88 treated trees in 1990 have wilted since 1990, whereas 42 of 80 control trees have wilted. Propiconazole was effective in 1990 as a preventive treatment for oak wilt in Q. rubra and Q. ellipsoidalis. Propiconazole was detected in the vascular tissue of a treated tree 12 months after injection using a thin layer chromatography (TLC) assay procedure; propiconazole was not detected 20 months after injection. Results from the assay procedure imply treatment with the fungicide would be required approximately once every 2 years.