Bleeding Trees: Microbial suspect named in beech deaths

A relative of the microbe that caused the Irish potato famine may be the killer in puzzling deaths of beech trees in the northeastern United States.

Plant pathologist George Hudler of Cornell University says that he’s been worrying for 30 years about occasional U.S. declines of century-old showpiece European beech trees. Thanks to a break in some recent cases, though, Hudler’s now naming a suspect: a Phytophthora.

Telltale symptoms of the disease include thin cracks in the bark that ooze sap and a startling pink shade to tissue just under the bark in fall, Hudler and his colleagues reported in Milwaukee this week at the annual meeting of the American Phytopathological Society.

European beeches grow into tall, rounded beauties from Virginia to Massachusetts and as far west as Ohio. “These are majestic trees,” says Hudler.

In the early 1970s, he began to receive occasional calls to examine huge beeches that turned into skeletons with little warning. Once a beech sickens, many microbes and insects rush to the feast, and Hudler couldn’t say which plague had struck first.

In the past several years, though, a few tree owners called in Hudler at a much earlier stage of beech decline. He and his colleagues sampled so-called bleeding cankers on some four dozen beeches in New York and Connecticut. Field tests, microscopic observation, and genetic sequencing all point to the genus Phytophthora.

Biologists used to classify these thread-like, spore-forming organisms as fungi, but recent molecular work has suggested a closer relationship to brown algae. The genus Phytophthora includes, besides the species that attacks potatoes, one that has alarmed the West Coast with sudden oak death (SN: 8/5/00, p. 86).

Hudler’s team says that the new results show that the beech pathogen is not an East Coast outbreak of the oak pathogen that’s triggered plant quarantines in California and Oregon. Hudler says, “I was really worried about that.”

Hudler recommends pampering a sick beech tree with soil improvements and plenty of water, but he’s testing antifungal treatments.

Pathologist Robert Linderman of the Agricultural Research Service in Corvallis, Ore., says he, too, thinks that the beech pathogen looks different from the Phytophthora that causes sudden oak death. Both diseases seem to start with bleeding cankers in bark, though. “It’s an odd coincidence,” says Linderman.