T he mail is full of worms — and that’s exactly what plant pathologist Robert Marra had hoped for when he cashed in on a favor. Marra works at the Connecticut Agricultural Experiment Station , based in New Haven, and he’s been cashing in a lot of favors recently. Gallon-sized Ziploc baggies of forest detritus — jumbles of leaves, buds, and twigs — are arriving at his laboratory from across the Eastern United States.

Marra carefully unpacks each delivery. Then, he starts hunting for worms. Marra is looking for Litylenchus crenatae mccannii, a microscopic roundworm, called a nematode, that preys on beech trees.

American beech are a widely beloved species that populate forests across the eastern third of the United States, and their highly nutritious nuts are a food source to more than 40 animal species, including wild turkeys and black bears. Advertisement But over the last 12 years, L. crenatae mccannii has taken up residence in beech forests, and it has multiplied at an alarming rate.

One scientist described it like a scene out of a horror movie: Picture a rain-soaked New England forest, where every blade of grass, every twig, and every stray bird feather is coated with slithering microscopic nematodes. Millions upon millions of worms. L.

crenatae mccannii is thought to be the cause of beech leaf disease , a highly infectious pathogen that can disrupt a tree’s ability to photosynthesize and therefore survive. In highly infested areas, the disease can kill up to 90.