When Erin and Jeff Zaruba decided to buy a home in Nicasio, California, the majestic 40-foot-tall coast live oak shading the backyard was nearly as appealing as the house. That's why they were heartbroken to discover that the leaves of their beloved oak had turned brown and its trunk was oozing reddish-black sap. Less than six months after the Zarubas moved into the house, the tree was completely dead. Says Erin: "It looked as if a bear stabbed it with its claws and ripped it apart."

The Zarubas and their tree are not alone. Tens of thousands of oaks across California are suffering from a mysterious disease. It causes huge sores, or cankers, that can kill a tree in just a few months. Officials at California's state parks are worried that the disease, known as Sudden Oak Death, could eventually kill the state's estimated 30 million live oaks, black oaks and tan oaks.

"You walk into a forest and see hundreds of trees bleeding to death," says Victor Marquez of San Francisco.

Scientists admit that they have never seen this disease before and don't know how to stop it. Since 1995, when Sudden Oak Death was first spotted, they have tried everything to halt its spread: spraying pesticides, injecting chemicals into roots, removing infected trees. To keep the disease from spreading outside California, state and federal officials were working on a plan last week to stop oak products from leaving the state.

The Root of the Problem
Detective work on the disease is paying off. University of California scientists have identified the cause: a fungus belonging to a group called Phytophthora (fy-toff-ther-a). It's related to the fungus that wiped out Ireland's potato crops in 1846. Phytophthora usually invades plants through the roots, but this type may be different. "We think the fungus may be splashing off the big trees in raindrops," says researcher David Rizzo.

Because Phytophthora can infect many types of plants, researchers fear the fungus will spread beyond oaks. It's already been spotted on a rhododendron and a huckleberry shrub. The Department of Agriculture has approved $3.5 million for research. Tree experts say much more will be needed to keep it from spreading across the U.S.

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March 30, 2001 World Report