There’s something iconic about driving through California’s Central Coast and seeing giant oak trees scattered across the landscape. Throughout history, however, not all Californians have appreciated the majesty and value of these trees. During the first half of the 1900s, many oak trees were removed to make way for agriculture and urban development. This, together with poor regeneration, contributed to declining populations of some of California’s 20 native oak species, most notably the valley oak.

https://www.growingproduce.com/fruits/what-oak-trees-mean-to-the-health-of-vineyards/?amp

Armillaria is a serious forest pathogen common throughout California, having evolved to live where native oaks have grown. It is a long-lived, parasitic fungus that survives off dead root material, eventually killing a susceptible host. It does not affect oaks unless they are already stressed by disease or overly-watered lawns underneath the canopy.

https://alamedasun.com/news/%E2%80%98tis-season-oak-root-fungus-strike