Understanding and Managing Sudden Oak Death in California

3.2. Reducing Disease Risk in Susceptible Stands

Once P. ramorum has become established in an area, only a few management practices have the potential to reduce disease risk to susceptible oaks and tanoak. These practices are primarily preventative, and may also be used in at-risk stands in which the pathogen has not yet been detected. Large scale field testing of these techniques is still ongoing, so the level of protection provided by these practices under various field conditions is still unknown.

3.2.1. Timing of Pruning or Other Wounding

Although P. ramorum readily attacks intact bark, unpublished research (Doug Schmidt and Matteo Garbelotto, U.C. Berkeley) indicates that large pruning wounds have an elevated risk of infection for about four months. Other wounds that expose inner bark or wood would likely show a similar pattern.

These results suggest that SOD risk may be increased if major pruning or other operations that cause bark wounds are conducted when P. ramorum spores are present. To minimize this risk factor, avoid such activities during the rainy season. Ideally, complete pruning or wounding at least four months before P. ramorum spores are likely to be present.

Many native canker rot and other wood decay fungi that colonize pruning wounds also sporulate during the rainy season. Pruning during the dry season also minimizes the risk that pruning wounds will be infected by wood decay fungi.