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Posts Tagged: oak

UC publication helps city folks living with oaks

The oak is a common symbol of strength and endurance, but some of the majestic trees in California are buckling under the pressure of urbanization, reported the Sacramento Bee this week.

The Bee's feature about the care and feeding of California native oaks was centered around the new UC publication "Oaks in the Urban Landscape," written by retired UC Cooperative Extension environmental horticulture advisor Laurence Costello, and co-authors Bruce Hagen and Katherine Jones. The 265-page book is available in the UC ANR Catalog for $55.

In most cases where urban environments are shaded by oaks, the trees towered over the landscape long before humans moved in. Costello said witnessing the heartbreaking decline of urban oak trees was a catalyst for writing the book.

"It's just a shame; they're such a beautiful tree and the symbol species of California," Costello was quoted in the story.

Costello provided reporter Debbie Arrington with basic tips for protecting oaks in urban environments:

  • Know what kind of species you have. "Is it a California native or imported? It makes a huge difference."
  • Don't surround a valley oak with lawn; irrigation three times a week can cause fungus problems in the root and crown.
  • Know where the oak roots are before installing a swimming pool or an irrigation line. Oak roots are very sensitive.
  • Use a layer of mulch – preferably bark – to keep oak roots comfortable.
  • Fertilizer is usually unnecessary and pruning can weaken trees.

Oak trees may seem needy, but Costello says they are worth the extra effort. California's oaks are difficult to regenerate and it can take centuries for trees to develop the massive canopies and enormous trucks found on the most highly valued oaks.

Although shade-tolerant turf can be used under oaks, it is best to replace the turf with mulch.
Although shade-tolerant turf can be used under oaks, it is best to replace the turf with mulch.

Posted on Thursday, August 18, 2011 at 6:05 AM
Tags: Laurence Costello (1), oak (2)

The agony of the oaks

As if life weren’t difficult enough for California’s majestic oaks, they now face a brand new adversary. Already burdened by drought, wildfires, firewood harvesting and Sudden Oak Death, the Riverside Press-Enterprise reported in December that goldspotted oak borer hitchhiked from Arizona or Mexico a few years ago and is now attacking Southern California oaks.

It was identified in the Golden State in 2006 and to date has besieged coast live oak, California black oak and canyon live oak, according to an article in the December 2009 issue of UC's Oaks 'n' Folks newsletter written by Doug McCreary, UC Berkeley Cooperative Extension natural resources specialist. So far, more than 17,000 oaks have succumbed to the borer.

Unlike pests that target weakened or stressed trees, the GSOB (also called "Golden SOB" by some, according to McCreary) attacks large, vigorous and healthy trees, including those in urban yards.

"We are turning a big crank on this bug right now," the Press-Enterprise article quoted Mark Hoddle, an entomologist and director of UC Riverside's Center for Invasive Species Research. "Can you imagine Southern California without oak trees? It would be a disaster."

Even more alarming, officials believe the pest's range in California will likely expand. It's progress can be slowed with the public's help. The Press-Enterprise published the following tips for stemming the spread of GSOB:

  • Do not transport oak firewood into or out of campgrounds or parks

  • Chip infested oak wood to 1-inch pieces

  • Cover stored oak firewood with 6 mm, UV-stabilized, durable plastic tarps in the spring. Secure all the edges of the tarp to the ground to prevent beetles from escaping

  • Season oak firewood. Remove the bark and place the wood in direct sunlight

The UCR Center for Invasive Species has created a Web page with information about and photos of GSOB and damage caused by the pest.

In addition, a two-page Pest Note on gold spotted oak borer, with 14 color photos, may be downloaded from the Web.

Goldspotted oak borer.
Goldspotted oak borer.

Posted on Wednesday, January 6, 2010 at 7:33 AM
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