Effect of an Introduced Ambrosia Beetle (Xyleborus glabratus) on Red Bay (Persea borbonia) Mortality in Maritime Forest Communities of St. Catherine's Island, GA
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Authors
Hess, Matthew
Issue Date
2007-05-02
Type
Thesis
Language
en_US
Keywords
barrier island , red bay , pathogen , American chestnut , American elm , St. Catherine's Island
Alternative Title
Abstract
Over the past three years, red bay (Persea borbonia, Lauraceae) populations along the Georgia coast
have experienced high levels of mortality due to an introduced fungal pathogen (Ophiostoma sp.) being
spread by outbreaks of a recently introduced, Asian ambrosia beetle, Xyleborus glabratus. The beetle
carrying the fungus was believed to have arrived in this country on shipping pallets and was first
identified in the port of Savannah, Georgia in 2002. Red bay is an abundant and ecologically important
tree species found in the coastal plain of the southeastern United States. This study represents the first
assessment of red bay decline, which as a casualty of an introduced pathogen, may be following the same
fate as American chestnut, American elm and flowering dogwood in the forests of the eastern U.S. Five
5000m2 plots were established on St. Catherine’s Island, a barrier island south of Savannah. The status of
red bay populations in these plots was assessed in 2004, 2005 and 2006 for leaf wilt, diameter at breast
height (DBH), and the presence of basal sprouts. It was determined from that red bay is a common
species represented in many size classes. Across the five study sites, the proportion of fully wilted red
bays increased from 0.06 in 2004 to 0.89 in 2006. A fitted logistic regression model for binary response
variables suggested that DBH was not a significant predictor of probability of infection (p>0.05), while
site and year were significant (p<0.05). The odds of basal sprouting on a dead tree in 2006 were 7.09
times higher than the odds of sprouting on a live tree. However, potential regeneration by basal sprouts
was severely limited by deer browse. A comparison with Dutch Elm Disease (DED) and other significant
tree losses suggest that red bay will likely meet the same fate. This will have serious consequences for the
already degraded maritime forest ecosystem in terms of species composition, structure and function.