Effect of Climatic Variables on Abundance and Dispersal of Lecanosticta acicola Spores and Their Impact on Defoliation on Eastern White Pine.

The disease complex white pine needle damage (WPND), first reported in 2006, has now escalated to an epidemic state across the northeastern United States. Although this complex is composed of several fungal species, Lecanosticta acicola is considered to be the primary causal agent. Knowledge regarding the epidemiology, specific climatic factors that affect the spread of L. acicola on eastern white pine (Pinus strobus) in natural forest settings, and potential risks repeated defoliation may have on tree health is limited. Therefore, this study examined how climatic variables affect the abundance and distance of spore dispersal of L. acicola and compared litterfall caused by defoliation versus natural needle abscission. Conidia were observed on spore traps from May through August, with a peak in abundance occurring in June, corresponding to the defoliation of second- and third-year foliage measured in litter traps. During peak spore production, relative humidity and the occurrence of rainfall was found to have the greatest influence on spore abundance. Our results will aid managers in determining how far from infected trees natural regeneration will likely be affected and predicting future disease severity based on climatic conditions.