Pine Pitch Canker
Pine pitch canker is a non-native plant pathogen that has was first identified in California in 1986. Since then it has spread to 18 California counties including San Mateo, San Francisco and Marin. The disease kills a variety of pine species and is having a dramatic effect on the bishop pine forests of Point Reyes National Seashore. Scientists are working to understand what impact this disease will have on our forests.
Sudden Oak Death (SOD)
First seen in Marin County in the mid 1990s, Sudden Oak Death (SOD) is now killing tanoaks, coast live oaks, Shreve oaks, canyon live oaks and black oaks in 13 coastal counties. In 2000, the cause of SOD was identified as the fungus-like pathogen Phytophthora ramorum. This extremely aggressive pathogen can kill an otherwise healthy tree in two years or less. Oaks and tanoaks that are infected with P. ramorum form bark cankers that may ooze a thick, dark reddish-brown liquid. Sick trees are also often invaded by bark beetles and fungus. P. ramorum spores spread from many other species, including California bay, coast redwoods, madrones, and rhododendrons that can host the pathogen, but are not harmed by it. In areas where SOD has been present for approximately a decade, tanoak mortality rates range from 35-60% and oak mortality rates range from 5-30%. Natural resistance in tanoaks is very low and SOD may eventually eliminate this species from coastal forests.
Oaks and tanoaks—and their nutritious acorns—play a vital role in Bay Area forests. The loss of these trees would be a serious blow to creatures such as birds, rodents, and squirrels that depend on them for food and shelter, as well as the owls, hawks, coyotes, and bobcats that prey on these creatures. Furthermore the dry dead trees and leaves may increase the frequency or intensity of wildfires. Because SOD was only recently discovered there is still much about it that remains a mystery. On-going research is looking at its causes, the exact nature of the disease cycle, and possible treatments.