Deadly Tree Disease Spreading Rapidly In Bay Area

KCBS Radio Afternoon News
November 07, 2019 - 4:38 pm
A California Live Oak tree spreads its limbs across the golden grassy hills of California

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A deadly disease could mean the end for millions of oak trees stretching from the Bay Area to Baja California.

UC Berkeley’s annual tree survey found the number of trees infected with the pathogen known as sudden oak death doubled in the last year, and in some areas the rate of infection had increased by as much as 10 times.

“It can take as little as half a year to kill a tree,” said UC Berkeley forest pathology professor Dr. Matteo Garbelotto. “When the pathogen gets to the main stem of oaks and tan oaks, it starts a process of eating away a circumference of the tree.”

Infected trees have been found in the East Bay as well as Marin, Napa and Sonoma counties, although San Francisco has been spared for now.

Signs of sudden oak death include pale leaves and new shoots that wilt and appear old.

The last two winters may be partly to blame for the rapid increase in the spread of the disease, as wet weather helps produce and spread the spores. 

“The microscopic spores are mostly produced when we get significant rainfall,” said Garbelotto. “The spores are picked up by droplets of rain and as the droplets of rain fall on the ground and fall on other plants, so do the spores."

The disease was first carried over to the U.S. on plants coming from Asia. It's estimated that millions of trees along the west coast have fallen to the disease since.

As the trees die, they leave behind kindling for wildfires.

Garbelotto said it’s unlikely that the disease can be eradicated. Billions of dollars have been spent in an effort to prevent the disease from spreading outside of the U.S. to uninfected countries.