Abstract
The southeastern United States has been experiencing unexplained sugarberry (Celtis laevigata) mortality for over a decade, representing one of the most severe and widespread Celtis mortality episodes ever reported from North America. Here we describe external symptoms, progression of mortality, and the known geographic extent of the problem. More than half of all trees monitored at one site within the affected area died over five years of observation. Although many trees died within a year of first exhibiting symptoms (e.g., small yellow leaves, branch dieback, premature leaf fall), many others continued living for years after becoming symptomatic. A preliminary insecticide trial found no improvements in survivorship among trees treated with insecticides, emamectin benzoate and imidacloprid, relative to control trees. Our findings suggest the problem will likely continue and become more widespread in the coming years.
Study Implications
Sugarberry mortality in urban and forested environments is an ongoing problem that has the potential to spread throughout the southeastern United States and perhaps more widely, depending on the susceptibility of other native Celtis species. Many trees die within a year of first showing external symptoms, whereas others can live for many years after appearing symptomatic. Declining trees in rights-of-way and public spaces are presenting costly hazards to cities, and canopy gaps in natural areas are likely to facilitate the establishment and spread of invasive plants. Studies aimed at determining the cause of this problem are urgently needed.
Progression of Sugarberry (Celtis laevigata) Dieback and Mortality in the Southeastern United States