Do anthropogenic nutrient inputs increase American beech susceptibility to BLD

Beech Leaf Disease (BLD) has spread rapidly across the northeastern United States since its first documentation in Ohio in 2012, leaving ecologists with an unresolved question: why are American beech trees declining so severely when the presumed causal nematode is present even on asymptomatic trees?

Most current research has focused on Litylenchus crenatae subsp. mccannii as the primary agent of disease. Yet mounting evidence suggests that nematode presence alone cannot explain the geographic pattern, severity, or progression of BLD. Nematodes are ubiquitous in forest ecosystems, and their detection on healthy beech trees raises the possibility that BLD is not driven by a novel pathogen, but by altered host susceptibility.

This paper explores the hypothesis that fertilizer-driven nutrient imbalance—particularly excess nitrogen and altered phosphorus availability—may be a critical predisposing factor in Beech Leaf Disease, weakening tree defenses, altering leaf chemistry, and creating conditions that allow nematodes to cause disproportionate damage. By examining landscape position, agricultural history, fertilizer use trends, and physiological responses of beech trees, this work reframes BLD as a cumulative, anthropogenic stress syndrome rather than a single-pathogen disease.

Rather than asking whether fertilizers cause BLD outright, this paper asks a more ecologically plausible question: have modern nutrient inputs shifted forest conditions enough to turn a native or benign organism into a lethal one?

How can we test it: