Sad Moos – Trees

December 22, 2009


Have you noticed the bare landscape in front of Woodside High? Sadly, there are no “Woods” along Woodside Road in front of the school anymore. The long row of stately trees had to be removed due to disease, a sadly familiar theme playing out in our town. The school will replace the trees with native California trees more resistant to disease. We can’t wait for this to happen as the school frontage looks so bare and bleak without them.

With this harsh reminder that the drought, Sudden Oak Death and a variety of other insects and diseases are killing our beautiful trees, we all need to do all we can to help our trees survive. Oaks, Evergreens, Madrones and even mighty Redwoods are having trouble, and with the very high value of having mature trees on your property, it is a time for concern.

We have written about our old nemesis Sudden Oak Death (SOD) before. Discovered in 1995, in tanoaks growing on a Marin homeowner’s property, it has a fungus like pathogen called Phytophthora ramorum (pronounced “phy-TOFF-thoruh ra-mor-um”). This very aggressive pathogen is related to organisms believed to be responsible for the Irish potato blight in the 1840s and to the current large-scale destruction of eucalyptus trees in Australia and oak trees in Europe.

In light of the fact that the chestnut blight largely made chestnuts extinct in American forests in a mere 40 years, this species of the notorious Phytophthora group should have us all worried. And it’s not just Oaks, there is concern that redwood forests may become infected. The role of the pathogen in redwoods is still not known but it is suspected that, while it may not kill adult redwoods, it affects redwood regeneration.
The common name, sudden oak death, is misleading since the pathogen affects more than oak trees and it typically takes more than a year for the tree to die. As a homeowner, however, the death of a once healthy tree may seem sudden because the leaves turn brown in a matter of weeks.

This pathogen has two diseases, one stem canker disease, which can kill adult species, and one foliar and branch disease that kills some but not all host plants. The most common symptom in tanoaks less than 20 feet tall is the wilting of new shoots. The shoot dies back, then falls off and new shoots appear from the dieback point, giving the tree a bushy appearance. As the tanoak leaves turn brown and the tree begins to die, there is often a canker located on the trunk not more than 15 feet from the ground. New sprouts often occur at the base of the dying tanoak but these sprouts will typically die, too.

In the true oak family, Coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), Shreve oak (Quercus parvula var. shrevei), the earliest symptom is a bleeding canker with a burgundy-colored to tar-black sap that oozes out on the bark. The bleeding will kill moss or lichen it touches, and is another sign to look for. The ooze may dry to a hard, dark mass and it may also wash off in a rainstorm.
Later, the tree will be attacked by very small (1/16- to 1/8-inch long) brown-colored beetles which leave a tell-tale trail of sawdust (called frass) on the bark. The tree will also be attacked by fungi. Old fungi may be hard and wart- like while new fungi will have powdery spores that rub off if touched. The pathogen kills the tree by effectively choking it.

You can find several links and video on our Mootube page under Public Service. You will find information on how to spray to protect your trees, how many trees are likely effected and where the outbreaks are.

So COW’s do what you can to keep the Woods in Woodside!

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