The situation was bleak two years ago when an upsurge in Dutch elm disease threatened to sweep through St. Helena's historic Tunnel of the Elms on Highway 29.

Trees were succumbing left and right. Unless money were found to pay for an expensive battle plan, a century's worth of arboreal splendor seemed destined for the mulcher.

Fourteen of 143 elms succumbed to Dutch elm disease before a community effort funded by the St. Helena Beautification Foundation came to the rescue.

Some $45,000 in treatment expenses later, the foundation is stepping back. Caltrans, the owner of the trees, and the city of St. Helena, which views the stately double row with pride, are now challenged to come up for a plan to save the trees for generations to come.

Dutch elm fungus still infects the tunnel's intertwined roots. It can be held at bay if each tree is treated annually with a fungicide and a pesticide to control the beetles that transmit the disease, said Joe Borden, owner of Britton Tree Services.

"These materials are 100 percent effective when you get proper application," Borden said.

Britton Tree Services will be applying a final dose of fungicide this fall, exhausting the funds raised by the St. Helena Beautification Foundation.

The city and Caltrans have begun negotiations on how to continue treatments in 2008 and beyond, said Bert Johansson, St. Helena city manager.

Beringer Vineyards, whose facilities border the Tunnel of the Elms, is likely to be a player in keeping the trees healthy, he said.

Caltrans is proposing that St. Helena take over responsibility for the trees, with the state helping to pay for ongoing treatment, Johansson said.

St. Helena is proceeding cautiously. Joe Haller, the city's parks superintendent, estimates it will cost $30,000 annually to maintain the tunnel, including chemical treatments, pruning, mulching, fertilizing and watering.

"There has to be some incentive to take on the liability," Johansson said. Because the trees are planted only a few feet from the roadway, cars routinely hit them, he said.

Caltrans watered and pruned the trees this year, while the city applied a non-nitrogen fertilizer to promote root growth, Haller said. Britton Tree Services provided a mulch that city workers spread on the root zone.

In recent weeks, a tree on the east side showed signs of branch death. Tests confirmed Dutch elm disease, so the tree will be removed, possibly this week, he said.

This death does not mean that the chemical treatments are not working, Borden said. The dying tree was likely infected before the chemical applications began in 2006, he said.

Bill Pramuk, a consulting arborist who has observed the Tunnel of the Elms for years, said the various governmental entities need to come together and map out a preservation strategy.

Absent a plan, "I'm getting a sinking feeling about the whole thing," he said.

Trees along the west side of Highway 29 are more vigorous than those on the east. They benefit from irrigation on the grounds of Beringer's Rhine House, tree experts said.

Ideally, irrigation will be extended to the east side. The St. Helena Beautification Foundation may help pay for irrigation materials, said president Joice Beatty.

Kathleen Kernberger, a local historian, said the elms were likely planted in the first decade of the 20th century. Tour guides at Beringer claim the trees were planted in the 1880s, but Kernberger is skeptical of the photographic evidence.

Borden said he counted 103 rings on the trunk of a recent Dutch elm casualty, suggesting the tree was planted in 1904.

American elms can live 200 years or more, suggesting that the Tunnel of the Elms has decades of additional life. But annual treatments will be needed to keep Dutch elm disease under control, Borden said.

Whoever planted the elms apparently did so without creating a stir, said Kernberger, who has surveyed newspapers of the time.

St. Helena officials are talking about planting disease-resistant replacement elms wherever there is a missing tree, but farther from the roadway. Over time, a replacement tunnel would be formed, but less susceptible to vehicle collisions, Johansson said. This would require cooperation with Beringer.

Saving the Tunnel of the Elms isn't a negotiable proposition, said Phoebe Ellsworth, a beautification foundation member. "They are precious. They are St. Helena," she said.