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White Pine Needle Damage (WPND) is a complex of foliar fungal pathogens that have established as a chronic disease impacting eastern white pine ( Pinus strobus L.) stands in the northeastern United States. With long-term ecological and economic impacts in mind, it is critical to quantify the negative effects of this disease on tree and forest health in order to make informed management decisions. We measured litterfall to determine the timing and magnitude of WPND-induced defoliation across four study sites in the northeastern US between 2014–2016. We measured N concentrations of needles cast throughout the 2014 growing season to estimate total litter N flux resulting from WPND. Additionally, to quantify growth declines we measured annual basal area increment (BAI) from six symptomatic study sites in the infected region. We found that WPND-induced defoliation in the months of June and July accounted for 47% of the total annual litterfall across the study sites, often exceeding normal needle senescence in October. Foliar %N in June and July was 0.78 and 0.84% respectively, significantly higher than October concentrations of 0.40%, suggesting incomplete resorption of N during the summer months. Untimely summer defoliations resulted in a mean estimated N loss of 0.92 g N m −2  yr −1 , representing 63% of the total growing season N input from foliage. Growth of symptomatic trees at all sites was reduced following outbreaks of WPND initiating between 2007–2009. Severely infected trees reduced BAI 25–73% compared to pre-outbreak years. Our results show that WPND-induced defoliation significantly alters litterfall and N dynamics of affected stands, and suggest that subsequent N limitation in addition to reduced foliar area greatly reduces annual wood growth within infected stands. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The foliar fungal pathogens associated with the disease complex known as White Pine Needle Damage (WPND) are causing widespread defoliation of eastern white pine ( Pinus strobus L.) in the northeastern United States and Canada. Presently, there are no specific management recommendations for addressing declining stand health relating to WPND induced defoliations. This study aims to test the effects of thinning at two different residual stocking densities (14 and 25 m 2  ha −1 ) on mitigating the negative impacts of WPND within infected stands. To quantify the impacts of WPND on individual tree health, we generated a composite health index score using response variables measured in the field and weighted according to their association with observations of WPND severity. Post-thinning changes in disease severity were used to evaluate the effectiveness of stand thinning to reduce pathogen pressure and promote overall tree vigor. Results show that thinning had a rapid positive effect on overall tree health, with no significant difference between thinning treatment levels in the first two years following tree removal. Severity of WPND was reduced by 35% in low-density residual thinnings in the second year of the study. Our findings suggest that thinning as a silvicultural tool to reduce stocking densities within infected stands can effectively promote overall tree health and maintaining proper stocking densities is recommended for stands at risk of infection. [ABSTRACT FROM AUTHOR]