Pitch Canker in California

Description

Pitch Canker in coastal California pine forests

Introduction:

The purpose of this project was to develop a system of permanent plots to track the impact and spread of pitch canker (caused by Fusarium circinatum) in native ponderosa pine (Pinus ponderosa), knobcone pine (P. attenuata), and Bishop pine (P. muricata) stands and in wildland and planted stands of Monterey pine (P. radiata) in California.

In 1998 and 1999, sets of ten permanent plots were established in native stands of ponderosa and knobcone pine in Santa Cruz County and Bishop pine in Marin and Monterey Counties.  These plots are of interest because they are dominated by species that have not been previously affected to a significant extent by this disease, and so they will provide baseline information on the impact of pitch canker on these hosts.  Eighteen additional plots were established in wildland and urban plantings of Monterey pine in and near the San Francisco Bay Area.  These plots were located on an east-west transect running from the coast in San Francisco and Marin Counties to inland areas in Contra Costa County.  The arrangement of these plots will provide data on the potential for pitch canker to develop on highly susceptible host species (Monterey pine) under warmer, drier conditions as compared to the moist coastal regions where the disease has already become severe.

Plots are located in stands of mixed age, ranging from old-growth to twenty-five year old trees. Within each plot, trees were tagged and rated for overall health and incidence of insect and disease problems, including pitch canker.  Since establishment, plots have been re-surveyed to monitor the development of pitch canker over time (in 1999, 2000, and 2002 for all plots, and also in 2005 for Bishop and ponderosa pine plots, and 2004 and 2006 for knobcone pine plots).

In 2001, an additional set of plots in Monterey pine wildland and urban settings was added to this project.  Previously, the maintenance of these plots was funded primarily by the Pebble Beach Company (where the plots are located).  These plots constitute one of the oldest plots sets for pitch canker monitoring in California.

Results:

As of 2003, there were low levels of pitch canker in only three of the ten knobcone pine plots (all other plots were uninfected), while only one Bishop pine plot (on the Monterey Peninsula) had a low level of pitch canker.  At that time, there was no pitch canker in any of the ponderosa pine plots.

Further analyses are in progress.