John Dawson, 61, of York, Pa., teaches math at Penn State's York campus and is an avid mushroom hunter.
"The attraction for some is edibility, a free meal," Dawson said. "For me, it's the challenge of identification."
Even scientists who study mushrooms have no clues as to how many kinds there are in the world.
"Only a small number are edible, and only a small number are poisonous," Dawson said. "The rest are too tough to eat, too tasteless or don't taste good."
Poison mushrooms give all species a bad reputation, he said.
The poison is slow-acting, wherein lies mushrooms' greatest danger.
"It takes about 24 hours before you know you've been poisoned," Dawson said. "By that time, it's too late. You're already high on the list for a liver transplant. The poison attacks the liver."
Dawson's favorite mushroom is the black chanterelle or black trumpet, a common variety found in midsummer.
About 15 of the 160 members at the weekend gathering are professional mycologists, Dawson said. Many are plant pathologists who study mushrooms to protect plant species.
Dawson said fungi nearly destroyed France's wine industry in the mid-19th century. They caused the Irish potato famine in the late 1800s and wiped out American chestnut trees in the early 20th century.
"Now, they're decimating live oaks in California," he said.
Amateur mushroomers are invaluable to professionals, Dawson said.
"They have an army of amateurs collecting for them," he said.
Dawson said members of his local club in Lancaster, Pa., are in the woods every other weekend from spring through late fall. In the winter, it's monthly lectures.
Ike Forester, 50, and his girlfriend, Becky Phillips of North Wilkesboro, N.C., drove up to Mont Alto for the weekend.
Forester, an amateur mushroomer, is president of the 2,000-member National Mycological Association.
Forester grew up on his family farm and knew nothing about mushrooms, he said.
"I walked those woods all my life and never even noticed them until a local community college came on the property to hunt them," Forester said. "They were picking baskets full of colorful mushrooms that I had never noticed."
Forester said he got hooked on the hobby after that.
"I enjoy hunting them, identifying them, cooking and eating them," he said. "I'm still an amateur, but I'm heavily involved."
Forester and Phillips started dating five years ago, and now she's as enthusiastic about mushrooms, she said.
"I never liked mushrooms, but he got me started," Phillips said. "You meet some very fascinating people in this hobby, young and old, and they are all learning."
Forester had one bit of advice for wood-be-mushroom hunters.
"Never eat one unless you are 100 percent certain it's not poisonous, and the best way to learn is to join a group like this," he said.