A synthesis of emerging health issues of eastern white pine (Pinus strobus) in eastern North America

Abstract

Eastern white pine (Pinus strobus L.) is one of the most important conifer species across eastern North America. However, emerging health issues of eastern white pine have increased dramatically in recent decades, raising serious concerns over the health and future of this species. These emerging issues are due to native pests and pathogens that were mostly innocuous in the past and hence, have been rarely studied. One fungal pathogen of concern, Caliciopsis pinea Peck, is associated with severe resinosis, crown thinning, dieback, cankers, and bark cracks/fissures. Reports of C. pinea have been on the rise since the mid-1990s, particularly in the northeastern U.S. An insect of concern, eastern white pine bast scale (Matsucoccus macrocicatrices Richards), is a sap-sucking pest associated with branch flagging, dieback, and canker formation. Although described as early as 1958, this insect was not reported in the southeastern U.S. until 2006, when it was found on eastern white pine with dieback symptoms. A foliar complex of fungal pathogens has also been on the rise since 2006 in the northeastern U.S. and southern Canada, known collectively as White Pine Needle Damage. This complex results in needle discoloration and necrosis, premature needle drop, and branch dieback. In combination, these emerging health issues are occurring at levels not previously reported and across several regions, indicating an imminent range-wide health concern for eastern white pine. Our goal is to synthesize the ecology, evolutionary and post-settlement history, silvicultural practices, and abiotic and biotic stressors of eastern white pine. By unifying the known ecology and stressors of eastern white pine, we aim to provide a forest health framework to assist resource managers in developing a cohesive conservation, management, and restoration plan for this critical conifer species in North America.