Infected Fagus grandifolia Leaf Litter is a Persistent Reservoir of Litylenchus crenatae Inoculum for Beech Leaf Disease in a Northeastern Hardwood Forest

The American beech (Fagaceae: Fagus grandifolia ) is a mast-bearing canopy tree species that plays a vital role in northeastern North American forest ecosystems. Beech leaf disease (BLD) is a newly emergent and fast-moving forest disease affecting millions of American beech trees. As the disease advances, there is a significant reduction of bud and leaf survival, leading to defoliation, reduction of the canopy, and eventually tree mortality. The causal agent, the foliar nematode Litylenchus crenatae (Lc), is regarded as a new invasive species with potential origins in Asia. In addition to its association with beech buds and foliage, this nematode may also exploit senescent leaves as a stable reservoir of inoculum on the forest floor. This study investigates a potential role for infected beech leaf litter in the spread of BLD by quantifying extracted nematode individuals, observing their survival in desiccated leaves over one annual cycle, and exploring environmental predictors that may be associated with their survival. In one northeastern forest, the leaf litter around 15 symptomatic trees were monitored. Living Lc were consistently extracted from leaf litter in every month sampled, and collection of viable nematodes persisted up to 14 weeks in desiccated leaf tissues. Predicted nematode survival was not significantly influenced by prior month’s precipitation, but both vapor pressure deficit and freeze-thaw cycles were correlated with Lc survival after desiccation. These findings identify infected beech leaf litter as a plausible environmental reservoir of viable Lc and suggest that natural desiccation process may not reliably eliminate the inoculum.