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    Author(s): Brice A. McPherson; Greg Biging; Maggi Kelly; David L. Wood
    Date: 2017
    Source: Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 25-26.
    Publication Series: General Technical Report (GTR)
    Station: Pacific Southwest Research Station
    PDF: Download Publication  (161.0 KB)

    Description

    Prior to 2000 the etiology, effects on host trees, and possible consequences for northern California’s forests of the syndrome known as sudden oak death were unknown. We designed a plot-based study to address these issues and to set a baseline for future evaluations.

    In March-April 2000 we established a total of 20 plots in two forested areas in Marin County: China Camp State Park [CCSP] (10) and Marin Municipal Water District [MMWD] (10). The host species monitored were coast live oak [CLO] (Quercus agrifolia) and California black oak [CBO] (Q. kelloggii) in both sites and tanoak [TO] (Notholithocarpus densiflorus) in MMWD. We employed symptom-based monitoring on every stem >2-cm DBH (1.37-m), twice per year through 2007, then once per year through 2015. Symptom categories were bleeding; bleeding plus ambrosia and bark beetle attacks; bleeding plus beetles plus Annulohypoxylon thouarsianum sporocarps; and death. Trees that died without these symptoms were classified separately. Between 2000 and 2015, asymptomatic CLOs (n = 683) decreased from 68.8% to 42.9% and mortality increased from 6.7% to 40.5%. For CBO (n = 52), asymptomatic trees declined from 82.7% to 47% and mortality increased from 1.9% to 40.8%. For TO (n = 132), the asymptomatic trees decreased from 62.9% to 21.9% and mortality increased from 6.1% to 62.3%. The percentages of symptomatic trees declined from 22.4% to 8.7% for CLO and 31% to 15.9% for TO.

    Of the CLOs that were asymptomatic in 2000 (n = 454), 22% were dead with SOD symptoms by 2015 and 10% were symptomatic. However, another 14% were in remission, which we define as cessation of bleeding for at least three years prior to 2015 in a previously symptomatic tree (in the absence of beetle attacks). Although the long-term durability of remission is not known, our previous estimates of CLO infection levels did not recognize the remission category.

    Publication Notes

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    Citation

    McPherson, Brice A.; Biging, Greg; Kelly, Maggi; Wood, David L. 2017. Long-term monitoring of sudden oak death in Marin County and the East Bay Hills. In: Frankel, Susan J.; Harrell, Katharine M., tech. coords. Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 25-26.

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