Title: Sudden oak death disease progression in oaks and tanoaks
Author: McPherson, Brice A.; Mori, Sylvia R.; Wood, David L.; Storer, Andrew J.; Svihra, Pavel; Kelly, N. Maggi; Standiford, Richard B.
Source: In: Frankel, Susan J.; Shea, Patrick J.; and Haverty, Michael I., tech. coords. Proceedings of the sudden oak death second science symposium: the state of our knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 379-382
Description: In March 2000, we established twenty disease progression plots in Marin County to monitor the progress of sudden oak death symptoms in coast live oak (Quercus agrifolia), California black oak (Q. kelloggii), and tanoak (Lithocarpus densiflorus) (McPherson and others 2005). Plots were located to encompass a variety of habitat types and species combinations, ten in China Camp State Park and ten in Marin Municipal Water District. We monitored every coast live oak (731), California black oak (52), and tanoak (181) with a stem diameter greater than 2.5 cm, four times a year. Trees were evaluated by symptom and not sampled for Phytophthora ramorum to avoid affecting disease progression. Bleeding coast live oaks were found to follow a consistent and predictable sequence: bleeding, then beetle colonization, followed by emergence of Hypoxylon thouarsianum reproductive structures, and then death. Results are reported for the period 2000 through 2003. For all three species, the combined number of bleeding and dead trees increased by 2003, with the greatest increases seen in tanoaks. The percentage of living coast live oaks that were bleeding remained relatively constant, at around 25 percent. The response of California black oaks was very similar to coast live oaks. The proportion of bleeding tanoaks increased from 39 percent to 72 percent. Through 2003, every plot with symptomatic coast live oaks in 2000 showed increased numbers of bleeding and dead trees. Approximately 50 percent of bleeding coast live oaks were under active attack by ambrosia and bark beetles (Coleoptera: Scolytidae) or showed past beetle activity during each March sampling period, from 2000 to 2003. Beetles had colonized every bleeding coast live oak that died during this study while each was still alive. Beetles colonized tanoaks much less consistently than coast live oaks during the study period. Structural failure on the main stem (bole) occurred in bleeding coast live oaks with a much greater frequency than in asymptomatic trees of this species, or in either bleeding California black oaks or tanoaks.
Keywords: California black oak, coast live oak, Phytophthora ramorum, survival analysis, tanoak
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McPherson, Brice A.; Mori, Sylvia R.; Wood, David L.; Storer, Andrew J.; Svihra, Pavel; Kelly, N. Maggi; Standiford, Richard B. 2006. Sudden oak death disease progression in oaks and tanoaks. In: Frankel, Susan J.; Shea, Patrick J.; and Haverty, Michael I., tech. coords. Proceedings of the sudden oak death second science symposium: the state of our knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 379-382
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