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Tree-Killing Pathogen In California Can't Be Stopped

David Rizzo

Large-scale tree mortality in northern Sonoma County, California

David Rizzo

Sudden oak death has killed millions of trees over hundreds of square miles in California. A new study shows forest managers can’t stop the damage now, but measures could have been taken to reduce it.

Sudden oak death has taken out millions of oak and tanoak trees along northern coastal areas of the state, including Marin and Sonoma Counties and Big Sur.

The fungal pathogen, first detected in 1995, causes tree trunks to crack open and canker, or bleed out sap. The only way to stop it is to cut down the affected trees.

A study published in the Proceedings of the National Academy of Sciences finds that if forest managers had done that by 2002, they could have stopped the disease from spreading, but it would have come at great cost over several years. Now it’s too late.

The study also identified where and how to fell trees to control the spread more effectively in the future. Sudden oak death is known to affect over one hundred species of trees and shrubs. Researchers say the death of large numbers of trees also exacerbates the fire risk in California.