Efficacy of basal girdling to control oak wilt fungal mat production in Texas red oak (Quercus buckleyi) in Central Texas

Abstract

Woodlands dominated by Ashe juniper (Juniperus ashei) and oaks, including Texas red oak (Quercus buckleyi; synonyms: Quercus texana, Quercus shumardii var. texana), serve as breeding habitat for the endangered golden-cheeked warbler (Dendroica chrysoparia) in central Texas. Oak wilt, caused by the fungus Ceratocystis fagacearum, is considered a threat to habitat quality for this warbler. Basal girdling was tested for controlling fungal mat production on Texas red oak and for reducing disease spread at the stand level. For 2 years, symptomatic trees were girdled by stripping bark from the lower trunks in late summer. Trees were inspected the following spring for mats. Basal girdling reduced the overall proportion of infected stems that produced one or more fungal mat from 9.7 to 2.5%. Among mat-producing stems, basal girdling reduced the mean number of mats per stem from 4.78 ± 0.73 (least squares mean ± 1/2 95% confidence interval) to 2.78 ± 1.34. Probability that a stem would produce one mat or more was positively correlated with dbh and was significantly reduced by the basal girdling treatment. Two years of treatment did not affect 3rd-year infection levels within treated stands. However, the study design we used could not exclude local tree-to-tree spread of the pathogen through common/grafted roots. We suggest that basal girdling, used as a stand-alone practice, may not be effective in controlling the local spread of C. fagacearum in central Texas woodlands. Copyright © 2008 by the Society of American Foresters.