"SOD is deadly for oaks and it's impacting many other species as well," states Matteo Garbelotto, an extension forest pathologist and adjunct professor at the University of California, Berkeley, and a leading researcher on SOD. Not long after the isolation of the microbe causing SOD by U. C. Davis Professor Dave Rizzo in 2000, plant pathologists began to suspect that while oaks were the direct victims of the disease, other plants were involved in spreading it. Plants from the rhododendron family were among the first host plants identified. "What we hypothesized and what we're now confirming," says Garbelotto, "is that SOD is not spreading via the oaks, but is instead using a huge range of native plants for reproduction."
In fact, research by Garbelotto and Rizzo indicates that nearly all of the main tree species in California's forests, as well as forest shrubbery and undergrowth, may act as hosts for SOD. SOD appears to use the leaves, branches and stems of these plants to reproduce, resulting in lesions and leaf discoloration. It doesn't kill the host plant outright, but scientists say repeated SOD infections are likely to weaken the plant over time, negatively impacting its growth and making it susceptible to other diseases and insects.
And the more host plants SOD is able to use, the greater its potential impact on California's forests and ecosystems. Says Garbelotto, "SOD's reproductive strategy may make it able to persist indefinitely in infested forests and may affec
Contact: Cindy Ash
American Phytopathological Society