Sudden Oak Death Description:

Sudden Oak Death (SOD) is caused by a water mold called Phytophthora ramorum. The disease is common throughout California and Oregon.


Oaks of various species can be affected by SOD. The most common oaks that SOD can be fatal to include:

  • Tanoak
  • Coast live oak
  • California black oak
  • Shreve’s oak
  • Canyon live oak

Biology & Symptoms:

SOD spreads through the transfer of spores. Spores can be spread by rainfall and flowing water, or even via a person’s shoes or clothing or on animals’ paws. The disease causes dieback and loss of the tree. Initial symptoms include cankers, leaf spots, and loss of foliage.


There is currently no cure for SOD, so prevention is key. Regular preventative treatments can be applied to help prevent SOD, as well as proper pruning, mulching or fertilization to optimize the tree’s overall health. Phosphonates, a non-nutrient form of phosphorus, can be applied to protect oaks from becoming infected with SOD. Ask an arborist about utilizing this approach to manage this disease.

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