Long-term monitoring of P. ramorum inoculum identifies spatio-temporal patterns of pathogen sporulation and proves that selective California bay laurel removal reduces risk of oak infection

Abstract

In 2005, eight 50 x 50 m plots, all with a significant component of California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.), were selected in the Soquel Demonstration State Forest, Santa Cruz County, California. Each plot contained a 5 m buffer zone around the edges and sixteen 10 x 10 m squares. A bucket was placed at the center of each square: buckets were filled with at least 5 L of water every 2 to 3 weeks, and five California bay laurel leaves were placed as bait in each bucket for 2- to 3-week periods throughout the year (or when leaf infection was ascertained to occur). In a preliminary laboratory experiment, it was determined that infection of four to five bait leaves corresponded to an inoculum level of at least 10⁴ sporangia, while infection of one to three leaves corresponded to inoculum levels at least one order of magnitude lower than 10⁴. In 2007, all California bay laurels were eliminated from four treatment plots, while four control plots remained untreated. Baiting occurred all year round until 2009 and then only between February and July until July 2011. In the course of the experiment, a total of 240,000 leaves from 128 baiting buckets were inspected for infection.

Parent Publication

• Proceedings of the sudden oak death fifth science symposium

Citation

Garbelotto, M.; Swain, S.; Schmidt, D. 2013. Long-term monitoring of P. ramorum inoculum identifies spatio-temporal patterns of pathogen sporulation and proves that selective California bay laurel removal reduces risk of oak infection. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. Proceedings of the sudden oak death fifth science symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: p. 121.