Environment & Science

A fungal infection is killing a quarter of LA County’s ficus trees — and it’s spreading

File: A ficus tree shades a park in Los Angeles.
File: A ficus tree shades a park in Los Angeles.
Andres Aguilar/KPCC

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The deadly botryosphaeria fungus has infected more than 25 percent of Los Angeles County’s ficus trees, the L.A. County Agricultural Commissioner’s office said this week. The fungus is airborne and spreads easily down rows of trees lining city streets.

Once infected, a tree has less than three years to live, Jerry Turney, the agency’s plant pathologist told KPCC. The fungus only infects woody plants, not humans or animals, he said.

As the fungus reproduces, it causes branch die-back disease. The disease kills trees from the inside out, forming round cankers inside the wood. Branch by branch, an infected tree dies and begins to rot before releasing fungus spores into the air. The spores then get carried by wind and rain, Turney said.

The problem gets exacerbated when the fungus attacks a tree that’s a part of a long row of ficus trees, jumping from tree to tree, he said.

The county’s thousands of ficus trees make up about 2 percent of its urban forest. Ficus microcarpa — the specific genus being targeted — have been popular in L.A. for more than 50 years.

“[Ficus] are very common,” Turney said. “You can hardly go to a neighborhood where they aren’t in the area.”

Native to China and Nepal, ficus trees were brought to L.A. and planted in rows by the dozens along some of the city’s busiest corridors, he said. Their thick canopies provide ample shade.

Some of the worst-affected spots are Alhambra, along Main Street in downtown L.A., and Pasadena along Green Street, Turney said.

“You might go to a neighborhood were none of the trees show symptoms,” he said. “Then you might go a quarter-mile, half-mile away and you hit a street, and the whole street is involved.”

Botryosphaeria fungus also commonly infects agricultural crops such as pistachios and grape vines, he added. 

In downtown Los Angeles, dozens of tall, healthy looking ficus trees provide a break from the sun along Spring Street. Keith Giles, a resident, walks his three shih tzu’s — Mona Lisa, Al Pacino and Gracie — by them almost every day. He said he would miss having the shade if the trees were to die.

“It’s a pretty stark environment with no greenery around,” he said. “That’s really the only greenery we have are these trees.”

But the tree’s roots also buckle and ruin sidewalks. Nicole Wilder, another resident, thinks a fungal epidemic might just be a good thing.

“They are just not the right tree for this environment,” she said. “Unfortunately, the mistake was made and now we’re all paying for it. If the fungus kills them, sorry!”

Last month, Burbank's city council voted to remove 400 ficus trees in Magnolia Park and replace them with another species, the L.A. Times reported. 

Once a street gets infected, there’s no stopping it, according to Turney. The fungus’ spread is only just beginning. Over the next decade or so, thousands more ficus trees are expected to die, he said.

Symptoms of a botryosphaeria fungus infection on ficus trees: