The American Tree Farm System will be offering a webinar on April 18 to discuss managing Thousand Cankers Disease. This is a newly identified fungal infection (Geosmithia morbida) that affects black walnuts (Juglans nigra). This disease is passed around by a tiny beetle called the walnut twig beetle (Pityophthorous juglandis).
The disease has not been found in the Central Coast, but there are several parts of California that have been affected, primarily in southern California and in the Central Valley.
The Thousand Cankers Black Walnut Disease website will provide you with the most current information and several photographs of both diseased trees and the vector beetle.
As always in these diseases, the best prevention for the spread of the disease is to keep untreated wood at the site of origin.