<p>Forest pathology specialist Matteo Garbelotto researches Sudden Oak Death in Marin County, Calif.</p>
<p>SAN FRANCISCO — On the rolling hills and low mountains of coastal Northern California, green and lush now after winter rains, live oaks, tan oaks, black oaks and madrones have been dying for more than two years. A mysterious microscopic organism that causes Sudden Oak Death has been found on a widening list of trees. Even the stately redwood, a California icon as well as a valuable timber product, may be vulnerable. But a far more troubling scenario is gaining currency among plant pathologists and federal regulators: that the disease will make its way out of California and infect the forests of the interior United States with potentially disastrous results.</p>