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New oak ailment to watch for.

New oak ailment to watch for

Beleaguered oaks in the San Francisco Bay Area face yet another fungus ailment. Recently, coast live oaks in the Santa Clara Valley have been displaying symptoms of a blight that affects the lower leaves of the tree; affected leaves bleach to a pale tan. In severe cases, the tree seems to be wearing a tan skirt.

The guilty fungus is a species of Cryptocline. Twigs and branches don't seem to be infected, as they are with Diplodia quercina, which causes dieback; Cryptocline is thus less threatening to a tree's health.

Studies on this and other oak leaf and twig blights are continuing, but as yet no chemical spray has been registered for use. So far, experiments with fungicides have not been effective on Cryptocline.

No one's certain whether stress--due to lack of water or other causes--is a factor in the disease; some experts feel that it is. In any event, best treatment is good care: occasional deep watering around the drip line during prolonged dry spells, adequate feeding, and a dry trunk base. With luck, new leaves in spring and summer will replace the blighted ones.

Photo: Lower half of oak canopy is discolored by fungus infection

Photo: Blighted leaves are bleached to a pale tan
COPYRIGHT 1986 Sunset Publishing Corp.
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Copyright 1986 Gale, Cengage Learning. All rights reserved.

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Publication:Sunset
Date:Apr 1, 1986
Words:212
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