A swift-moving disease threatens California's signature tree, among others. Caused by a fungal species in the genus Phytophthora (fy-tof-thor-a). Formerly classified as fungi, phytophthoras are adaptable and aggressive algae-like pathogens.  At least two related species attack oaks inadvertently overwatered by homeowners caring for their lawns, and the symptoms mimic SOD. Still, this phytopthora could spread faster and further than most. Its spores are carried by soil and rain-splash and may be airborne as well. Often the first sign is black or burgundy sap oozing from tiny holes in the bark; soon after, the tree wilts, turning starkly brown.

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