TACOMA (AP) — Something is killing bigleaf maples — Washington’s biggest broadleaf tree — and scientists can’t stop it. They don’t even know what’s causing it. “We’ve looked for everything we can possibly think of and what people smarter than us can think of,” said Amy Ramsey, a forest pathologist with the state Department of Natural Resources. From British Columbia to California, stands of bigleaf maples are dying, leaving bald patches in the forest canopy or even denuded hillsides. Reports of dying and dead maples first reached the DNR in 2010, Ramsey said.