When planning or evaluating SOD management activities, you will need to consider if weather conditions over the previous several years have been favorable for SOD development. As discussed in Part 1, the likelihood that P. ramorum will initiate many new cankers or spread into new areas varies from year to year based on amount and timing of spring rainfall.
SOD prevention treatments are most successful when applied to trees that are not infected. Within one to two years of favorable SOD infection conditions, many infected trees will not yet have external symptoms and will appear healthy. In contrast, after several dry years with low inoculum production, most trees without symptoms are likely to be noninfected.
To evaluate the effectiveness of SOD prevention treatments, you need to monitor both treated areas and similar untreated control areas. During periods of low disease pressure, you will not be able to tell if SOD prevention treatments are working because even untreated trees are unlikely to develop symptoms. Trees need to monitored for at least several years after one or more seasons of high disease pressure to determine whether treated trees show less disease than untreated controls.