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Fuzzy caterpillars munching Palo Alto oaks

Future tussock moths infest trees, land on cars and creep out people

At the intersection of Homer Avenue and Kipling Street, caterpillars dangle in the air, crawl on the ground and teem on trees. They catch on passersby and swarm on parked vehicles.

Their leaf gorging is audible -- crunching, crackling, sizzling.

Barbara Lockwood lives downtown and walks by the intersection about three times a week to visit her mother. The caterpillars first appeared last week, but were particularly prominent Tuesday, she said.

"They're just all over," Lockwood said, noting her mother had to pick the caterpillars off her when she arrived.

The fuzzy, inch-long caterpillars, with black antennae and usually four cream or yellow dots on their backs are western tussock moths, according to Stanford University Grounds Manager Herb Fong.

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The oak trees near Homer and Kipling aren't the only local infestation.

The caterpillars can be found along Alma Street near El Palo Alto, at Gamble Garden, and near the chemistry building and athletic department on the Stanford campus.

"This is going to be a huge year," Palo Alto Managing Arborist Dave Dockter said, noting that the dry weather has contributed to the explosion.

Fong said this is the second year of a heavy tussock moth infestation. The population swells cyclically, he said.

Tussock-moth caterpillars dine primarily on oak leaves, but will also eat manzanita and other foliage, Fong said.

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Infestations usually don't kill the trees, he said. It would take about three or four defoliations in one year to kill a mature tree, Fong said.

The caterpillars are annoying and noxious, however. The hairs can irritate some people and if a rash develops, a doctor should be consulted, Fong said.

To combat the moths, Dockter and Fong suggest spraying the tree with a hose, raking up the caterpillars and disposing of them.

"There's not much that can be done," Dockter said.

He said soapy water or, if necessary, a "Bt"-based insecticide could be used.

Fong said Stanford ground workers have experimented by introducing predators of the moths. He said it is too early to know if their efforts are going to be successful.

"Several different things such as spiders and soldier beetles that are working on these pests (are) having a fairly easy time of eating," Fong said.

And for the non-squeamish, Fong said some of the caterpillars are even infected with a virus.

"They're shriveled and they seem a little lethargic and less active," he said.

The caterpillars, whose off-white fuzzy cocoons pock some trees, will pupate into adult moths in a few weeks, Fong said. Those adults, however, will lay more eggs.

This season could see three or more cycles of infestation, Dockter said.

Another oak pest, the California oak worm is just hatching now. They are green and smooth. Dockter said a large oak worm infestation is also possible.

The porch and front yard of the Women's Club of Palo Alto are covered with the critters.

Member Emily Renzel said the caterpillars were also bad last year and the club plans to try to control the infestation.

For tree-care tips, visit the city's Technical Tree Guide at www.cityofpaloalto.org/planning-community/tree_technical-manual.html.

(Staff Writer Becky Trout can be e-mailed at [email protected])

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Fuzzy caterpillars munching Palo Alto oaks

Future tussock moths infest trees, land on cars and creep out people

by /

Uploaded: Wed, Apr 4, 2007, 11:30 am

At the intersection of Homer Avenue and Kipling Street, caterpillars dangle in the air, crawl on the ground and teem on trees. They catch on passersby and swarm on parked vehicles.

Their leaf gorging is audible -- crunching, crackling, sizzling.

Barbara Lockwood lives downtown and walks by the intersection about three times a week to visit her mother. The caterpillars first appeared last week, but were particularly prominent Tuesday, she said.

"They're just all over," Lockwood said, noting her mother had to pick the caterpillars off her when she arrived.

The fuzzy, inch-long caterpillars, with black antennae and usually four cream or yellow dots on their backs are western tussock moths, according to Stanford University Grounds Manager Herb Fong.

The oak trees near Homer and Kipling aren't the only local infestation.

The caterpillars can be found along Alma Street near El Palo Alto, at Gamble Garden, and near the chemistry building and athletic department on the Stanford campus.

"This is going to be a huge year," Palo Alto Managing Arborist Dave Dockter said, noting that the dry weather has contributed to the explosion.

Fong said this is the second year of a heavy tussock moth infestation. The population swells cyclically, he said.

Tussock-moth caterpillars dine primarily on oak leaves, but will also eat manzanita and other foliage, Fong said.

Infestations usually don't kill the trees, he said. It would take about three or four defoliations in one year to kill a mature tree, Fong said.

The caterpillars are annoying and noxious, however. The hairs can irritate some people and if a rash develops, a doctor should be consulted, Fong said.

To combat the moths, Dockter and Fong suggest spraying the tree with a hose, raking up the caterpillars and disposing of them.

"There's not much that can be done," Dockter said.

He said soapy water or, if necessary, a "Bt"-based insecticide could be used.

Fong said Stanford ground workers have experimented by introducing predators of the moths. He said it is too early to know if their efforts are going to be successful.

"Several different things such as spiders and soldier beetles that are working on these pests (are) having a fairly easy time of eating," Fong said.

And for the non-squeamish, Fong said some of the caterpillars are even infected with a virus.

"They're shriveled and they seem a little lethargic and less active," he said.

The caterpillars, whose off-white fuzzy cocoons pock some trees, will pupate into adult moths in a few weeks, Fong said. Those adults, however, will lay more eggs.

This season could see three or more cycles of infestation, Dockter said.

Another oak pest, the California oak worm is just hatching now. They are green and smooth. Dockter said a large oak worm infestation is also possible.

The porch and front yard of the Women's Club of Palo Alto are covered with the critters.

Member Emily Renzel said the caterpillars were also bad last year and the club plans to try to control the infestation.

For tree-care tips, visit the city's Technical Tree Guide at www.cityofpaloalto.org/planning-community/tree_technical-manual.html.

(Staff Writer Becky Trout can be e-mailed at [email protected])

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