SOD Blitz 2025 Survey Results

SOD BLITZ 2025 meeting

Sudden Oak Death Blitz Results Meeting 2025.mp4

SOD Distribution maps

2025 SOD Blitz map (download link, requires Google Earth)

2008-2025 SOD Blitz map (download link, requires Google Earth)

SODmap: updated version TBA

Calinvasives Phytophthora ramorum map

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Table of 2025 SOD Blitz results

2025BlitzResultsTable.xlsx

Comparison Table (2024-2025) of SOD Blitz results

6-2025BlitzResultsCOMPARISON TABLE.xlsx

Table of samples not included in map

7-Samples not included in maps or tables 2025 SOD Blitz.xlsx

Results of 2025 SOD Blitz at a glance

The 2025 SOD blitzes were a huge success with an increase in the number of trees sampled, highlighting the current and continued relevance of the program and of the disease it addresses. Unfortunately major cuts in federal funding only allowed us to test 75% of all samples received.

The overall results indicate that we are currently in an epidemic phase of the disease, given that the % of SOD+ samples has doubled for two years in a row, since 2023. The State average percentage of SOD+ infectious bay laurels and/or tanoaks is 26.1 % (33% excluding areas without SOD). This is the third highest percentage of infection ever recorded in the 18-year history of the SOD Blitz program. Based on previous years’ data and on experience, when the local rate of bay laurel trees positive for the SOD pathogen goes over 20%, oak infection is likely to occur. Oak infection does not occur in dryer years when bay laurels sod positive rate is below 20%.

Currently, the risk of oak infection is HIGH for Big Sur, West Sonoma, Santa Cruz Mountains, Carmel, North San Francisco, Peninsula, Marin Co., Santa Cruz Co., Del Norte Co.(no oaks) and LOW-MEDIUM for the San Francisco East Bay, Mendocino, Co. East San Francisco Peninsula, East Sonoma Co. This is a good year to treat your oaks and remove bay laurels which may be growing 15-30 feet around them (60 feet for monumental oaks).

The spread and permanence of the disease continue to be greatly affected by the climate, with warmer areas being less impacted ( see Mount Diablo, South San Francisco Bay) while cooler, wetter areas are experiencing higher levels of the disease. It has been shown that rainfall favors the spread of the disease and that warmer temperatures slow the spread of the disease. However, current data are based on the NA1 lineage of the pathogen. Unfortunately, in the last 4 years, California has been dealing with the introduction and spread of two different lineages of the pathogen. In del Norte County, the NA1 lineage has doubled its range since it was first detected in the 2019 SOD Blitz. During the 2024 SOD Blitzes, five NA2 outbreaks were detected in the San Francisco Bay Area. Based on 2024 data, only one such outbreaks had a diameter of over 1 mile. However, the 2025 SOD Blitzes have determined that four out of the five outbreaks have diameters close to or larger than one mile, with one outbreak North of Woodside possibly having a diameter of at least 2.5 miles and possibly consisting of four separate outbreaks. An outbreak in the North Peninsula measures at least 2 miles in length. The differences in estimated size of the NA2 outbreaks between 2024 and 2025 are mostly due to under sampling in 2024 and not to annual spread of the pathogen, although some of that may have occurred in one year. Many ownerships are now affected by NA2, which, based on lab tests, is more infectious, especially at warmer temperatures. Best Management Practices need to be put in place to ensure we do not facilitate the spread of NA2 in California. The NA2 has also been reported in del Norte County by UCCE, Calfire and CDFA.

One nursery in the East Bay near one NA2 outbreak had its plant stock tested and all plants were negative, but multiple bay laurels in the property are positive for the SOD pathogen, although -fortunately- it is the NA1 lineage that has affected these bay laurels. Two nurseries in San Francisco were found to be negative as well. San Luis Obispo County remains negative for the pathogen, in spite of excellent and thorough testing of bay laurels and tanoaks. As reported above, the iconic Mount Diablo State park was also negative and the area around Sunol was also uninfested. Spread of the disease on foliar hosts such as bay laurels, tanoaks, toyons, Pacific madrones, Redwoods and many ornamentals is predicted to be significant in all areas having either HIGH or LOW-MEDIUM oak infection risk. With the exception of Tanoaks, foliar hosts suffer a very mild disease when infected by the SOD pathogen, however spread on these foliar hosts may in the end allow the pathogen to infect oaks in new spots or even locations.